22nd International Conference on Transparent Optical Networks ICTON 2020 and 12th Sub-Wavelength Photonics Conference SWP 2020 and 2nd Conference on Advanced Fibre Lasers and Coherent Sources (AFLaser) and 2nd International Conference on Dielectric Photonic Devices and Systems Beyond Visible (D-Photon 2020)   Bari, Italy, July 19-23, 2020

Co-located with:

• NEW! 1^st Workshop on Progress in Nonlinear Photonics and Applications (PNPA)
  
• NEW! 1^st Workshop on Photonic Technologies for Future Sustainable High-Capacity Metro Networks (PhotoMAN)
  
• NEW! 1^st Workshop on SDN-NFV Challenges and Solutions (SDN-NFV)
  
• NEW! 1^st Workshop on Softwarization and Virtualization of Optical Access Networks (OptSoft)
• NEW! 1^st Workshop on Microstructured optical fibers (MOF)
  
• 2^nd Workshop on Integration of Optical and Satellite Communication Systems into 5G Edge Networks (OSCto5G)
• 2^nd Workshop on Quantum Communications (QC)
• 2^nd Workshop on Multi-band Open Optical Networks (MOON)
  
• 2^nd Workshop on Machine Learning for Optical Communications (MALOC)
• 2^nd DFG MARIE workshop on THz Photonics (TP)
  
• 3^rd Workshop on Optical Microscopy Techniques (OMT)
• 4^thWorkshop on Novel Optical Amplifiers (NOA)
• 4^th Workshop on Label-Free Super-Resolution and Sensing (LFSRS)
• 4^th Workshop on High Capacity SDM-WDM Optical Networking (SDM-WDM)
• 4^th Workshop on Flexible and High-Capacity Optical Networks (Flex-ON)
• 5^th Workshop on Fiber-Wireless Network Technologies and Architectures towards 5G and Beyond (FiWiN5G)
• 5^th Workshop on Quantum Photonics (QPhot)
• 5^th Workshop on Multi-Layer Network Orchestration (NetOrch)
• 6^th Workshop on Technology for Data Center Interconnects (DACINT)
• 6^th Workshop on Datacenter Networks (DCN)
• 6^th Workshop on 5G Transport Networks (5GT)
• 7^th Workshop on Big Data Analytics and Network Optimization (BigNeO − former NeO)
• 10^th Anniversary Workshop on Green Optical Communications (GOC)
  
• 10^th Anniversary Special Session on Microwave Photonics (MWP)
• 11^th Workshop on Communication in Transportation Systems (CTS)
• 12^th Workshop on Broadband Access (former ACCORDANCE)
• 13^th Special Session on Market in Telecommunications (MARS)
• 15^th Nanophotonics for All-Optical Networking Workshop (NAON)
• 15^th Special Session on Photonic Atoms & Molecules (PAM – former Microresonators and Photonic Molecules, MPM)
• 15^th Special Session on Novel Glasses for photonic devices
• 16^th Reliability Issues in Next Generation Optical Networks Workshop (RONEXT)
• 16^th Optical Wireless Workshop (OWW – former Free-Space Optics Session)
• 16^th Photonic Integrated Components & Applications Workshop (PICAW)
• 17^th Global Optical & Wireless Networking Seminar (GOWN)
• 19^th European Symposium on Photonic Crystals (ESPC)
• 19^th Workshop on All-Optical Routing (WAOR)
  

ICTON invited presentations:

José Altabás

Roadmap for next generation optical networks based on quasi-coherent receivers
J. A. Altabas¹, O. Gallardo¹, G. Silva Valdecasa^1,2, M. Squartecchia¹, D. Izquierdo^3,4, S. Sarmiento⁵, M. Barrio⁴, J. A. Lazaro⁵, I. Garces⁴, and J. B. Jensen¹
Quasi-coherent receivers have been demonstrated as a powerful technology for addressing the requirements of the current optical networks based on 10 Gbps line rate. The quasi-coherent technology also has a promising future in the next generation of optical networks where the line rate scales up to 25 Gbps or 50 Gbps. In this paper, the current 10 Gbps quasi-coherent technology has been summarized, together with the first results at 25 Gbps. In addition, this paper shows the roadmap of the future updates of the quasi-coherent technology addressing the necessities of the future optical networks.

Mihai Bănică
Network visualization for optical transport networks
M. Bănică and V. Croitoru
Human interpretation of the network condition plays a key role in managing the network and services; information visualization allows network administrators to understand the behaviour of the managed network. Optical transport networks are inherently multivendor and multidomain networks, and the associated network management functions often make use of different databases and ways of information representation. In this paper we propose a method to optimize and enhance the information visualization, which allows for a unified and common information representation for the network management functions.
Keywords: optical transport networks, network visualization, network management.

Ignac Bugar
High contrast all-optical cross-switching of C-band femtosecond pulses in highly nonlinear soft glass dual core optical fibre
M. Longobucco^1,2, I. Astrauskas³, A. Pugžlys^3,4, D. Pysz¹, F. Uherek⁵, A. Baltuška^3,4, R. Buczynski^1,2, and I. Bugár^1,4
1Department of Glass, Łukasiewicz Research Network - Institute of Electronic Materials Technology, Warsaw, Poland
²Department of Geophysics, Faculty of Physics, University of Warsaw, Poland
³Photonics Institute, Vienna University of Technology, Vienna, Austria
⁴International Laser Centre, Bratislava, Slovakia
All-optical switching of 77 fs pulses centered at 1550 nm, driven by 270 fs, 1030 nm pulses in dual-core optical fibre exhibiting high index contrast is presented. The switching is achieved by nonlinear balancing of dual-core asymmetry. High switching contrast exceeding 20 dB is attained with driving pulses of only few nanojoule energy, which is due to the fibre core made of soft glass possessing high nonlinearity.
Keywords: all-optical switching, dual-core optical fibre, soft glass optical fibre, nonlinear directional coupler, ultrafast nonlinear optics, nonlinear cross interaction.

Ivan Cano
Laser-modulated EML for high output power transmitters
I. N. Cano, Huawei, Munich, Germany
We use a conventional externally modulated laser (EML) device with a novel dual-drive scheme to increase the achievable output power before saturation effects in the electro-absorption modulator degrade the signal quality. Both the laser and modulator section of the EML are driven together to generate a 10 Gbit/s intensity modulated optical signal. We compare the performance with conventional driving of the device whereby the modulator is driven with data and the laser is continuously on. Using the dual-drive scheme we are able to improve the mean modulated output power by 3 dB, compared to conventional driving, while still maintaining high extinction ratio (> 9 dB) and a low optical path penalty (< 1 dB).

Piero Castoldi
Network slicing in SDN networks
D. Scano, L. Valcarenghi, K. Kondepu, P. Castoldi, and A. Giorgetti
Scuola Superiore Sant'Anna, Pisa, Italy
Software Defined Networking is the candidate technology for implementing network slicing on a common network infrastructure for deploying a number of services with different requirements (e.g., 5G services). This work proposes a framework to deploy a set of network slices on an SDN network controlled by a single controller. Deployed slices guarantee isolation in terms of connectivity and performance. The proposed solution has been tested on an emulated SDN testbed utilizing the ONOS controller.

Peter Cochrane
Evolving network security
P. Cochrane and M. Abdel-Maguid
University of Suffolk, Ipswich, UK
In an ideal world the design and engineering of networks would include a comprehensive consideration of all security aspects and known requirements. These would then be integral into the basic net design at all levels. But this not the case! Such is the speed of technology progress and changing demand for new services and transport, designers are on the back foot and continually engaged in retrospective fixes. Two recent examples are the optical networks of the 80s and 90s designed to support the PSTN and modest Data Transmission that have been overtaken by IP networking and the WWW. More recently, the arrival of 5G has sparked the demand for a 10 – 100 fold increase in the capacity of FTTH/FTTP along with the abandonment of copper, GPON and BPON systems. At the same time the emergent properties of the IoT are creating even more stochastic chaos. “It is widely assumed that optical fibre provides the ultimate secure and stable channel, but this is not always the case” Along with all these changes are attendant security risks that see a rapidly rising catalogue of ‘patch solutions’. To tackle the many new and emergent risks we propose a number of new strategies based on the premise that fibre rich networks offer new levels of path and connection diversity, whilst AI has the ability to recognise network and connection anomalies on the fly.
Keywords: network design, local networks, last mile, core networks, fibre hacking, cloud computing, net traffic patterns, diverse routing, reliability and routing, common mode failures, 5G, mobile, IFTTH, FTTP, AI, IP, UDP, WWW, IoT, emergent properties.

Ivan Glesk
Investigation of 2D-WH/TS OCDMA system performance under the influence of PMD
I. Glesk¹, S. Seyedzadeh¹, J. Dubovan², M. Dado², and W. C. Kwong^3
1Electronic and Electrical Engineering Department, University of Strathclyde, Glasgow, UK
²Faculty of Electrical Engineering and Information Technology, University of Zilina, Slovakia
³Department of Engineering, Hofstra University, Hempstead, NY, USA
In this paper we analyse the performance of two-dimensional wavelength-hopping time-spreading (2D-WH/TS) incoherent optical code-division multiple-access (OCDMA) codes based on picosecond multi-wavelength code carriers under the influence of the polarization mode dispersion (PMD) in a commercially used optical fiber link operated by a data carrier provider. Based on the analysis of the experimental data followed by simulations we then propose design rules to minimise the PMD detrimental effects on the overall OCDMA system performance.

Miguel Gonzalez-Herraez
Underwater seismology using submarine dark fibers
R. Magalhaes¹, M. R. Fernandez-Ruiz¹, L. Costa¹, H. F. Martins², A. Garcia-Ruiz¹, S. Martin-Lopez¹, E. Williams³, Zhongwen Zhan³, R. Vantilho⁴, and M. Gonzalez-Herraez^1
1Department of Electronics, University of Alcala, Alcala de Henares, Spain
²Instituto de Óptica, CSIC, Madrid, Spain
³Seismology Laboratory, California Institute of Technology, Pasadena, CA, USA
⁴Marlinks, Leuven, Belgium
We review our recent work on chirped-pulse distributed acoustic sensing for the characterization of teleseismic and microseismic activity, particularly in submarine environments. We show that this tool may bring orders-of-magnitude more seismic data from the sea bottom, that could lead to a new understanding of the deep Earth's interior.

Norbert Hanik
Stability of the full spectrum nonlinear Fourier transform
B. Leible, D. Plabst, and N. Hanik
The Institute for Communications Engineering, Technical University of Munich, Germany
With the seemingly inevitable capacity crunch for state-of-the-art fiber optical systems, alternatives to wavelength-division multiplexing are widely discussed in the community. One of the proposed ideas that gained significant attention is the use of modulation schemes based on the nonlinear Fourier transform. For such a nonlinear frequency division multiplexing scheme, the time domain signal is generated from modulated continuous and discrete nonlinear spectra. We study the numerical behaviour of the used full spectrum nonlinear Fourier transform algorithm and propose optimizations to stabilize the forward- and backward transformation, in order to increase the feasible set for signal design.

Rongqing Hui
Spectral properties of quantum-dots mode-locked diode lasers and the impact in fiber-optic systems
Rongqing Hui¹, M. Al-Qadi¹, M. O'Sullivan², and Chongjin Xie^3
1Dept. Electrical Engineering & Computer Science, University of Kansas, Lawrence, USA
²Ciena Corporation, Ottawa, Canada
³Alibaba Infrastructure Service, Alibaba Group, Sunnyvale, USA
Coherent optical frequency comb based on semiconductor quantum-dots mode-locked laser (QD-MLL) is a promising device, which is able to provide a large number of equally spaced spectral lines simultaneously. We have measured the spectral properties of QD-MLL, including relative intensity noise, phase noise of each individual spectral line, as well as differential phase noise between spectral lines. More specifically, we report the frequency-dependent nature of QD-MLL phase noise, and its impact in the performance of fiber-optic communication systems.

Andreas Ioannou
All-in-fiber fabrication of cladding devices and components using femtosecond laser pulses
A. Ioannou^1,2, A. Theodosiou², C. Caucheteur¹, and K. Kalli^2
1Electromagnetism and Telecommunication Department, Faculté Polytechnique, University of Mons, Belgium
²Photonics and Optical Sensors Research Laboratory (PhOSLab), Cyprus University of Technology, Limassol, Cyprus
Femtosecond (fs) lasers are well suited for high-resolution inscription in transparent materials of all types, and in particular optical fibres. The “inscribe and step”, Plane-by-Plane (Pl-by-Pl) inscription method enables the fabrication of components, such as cladding waveguides (CWGs), cladding Mach-Zehnder interferometers (MZIs) and embedded waveguide Bragg gratings (MZI -FBGs), using the same key femtosecond laser parameters. The cladding waveguides structures were inscribed in such proximity for the fiber core that allowed evanescent coupling to occur. Having this operational principle, the compound cladding sensor has minimal effect on fiber strength, leading to a robust sensing device. Furthermore, the versatile femtosecond laser-inscribed cladding waveguides and ultra-compact MZIs that can support functional, integrated fibre Bragg gratings (FBGs). This method ensures a single inscription process, offering reliability and repetition in component manufacturing. This hybrid configuration is capable of measuring multiple parameters using the same demodulation equipment, with very high sensitivity while minimizing cross sensitivity issues. We focus on the response to changes in temperature, strain, bend, surrounding refractive index and relative humidity of the developed components.
Keywords: femtosecond laser inscription, fibre optics sensors, fibre Bragg gratings, microstructure fabrication, optical design and fabrication, cladding components.

Ognjen Jovanovic
Optimization of fiber optics communication systems via end-to-end learning
O. Jovanovic, R. T. Jones, S. Gaiarin, M. P. Yankov, F. Da Ros, and D. Zibar
DTU Fotonik, Technical University of Denmark, Lyngby, Denmark
The main limiting factor in fiber optic communication systems are the nonlinear transmission impairments, also known as the nonlinear Kerr effect. In order to deal with these impairments end-to-end learning is used with two approaches taken into consideration. The first approach is using a standard optical fiber communication system with conventional pulse shaping and autoencoders to optimize geometric constellation shaping, providing a solution robust to nonlinear optical impairments. While, in the second approach end-to-end learning is used to jointly train a nonlinear Fourier transform (NFT) based transmitter and a neural network (NN) based receiver. Optimization of the geometric constellation shaping provided gains up to 0.13bit/4D numerically and 0.12bit/4D experimentally. While for end-to-end learning optimized transceivers for NFDM systems improvement of up to two orders of magnitude are achieved in respect to bit error ratio.
Keywords: optical communication, neural networks, constellation shaping, nonlinearity compensation.

Joseph Kahn
Impact and mitigation of polarization- or mode-dependent gain in ultra-long-haul systems
H. Srinivas¹, E. S. Chou¹, D. A. A. Mello², K. Choutagunta¹, and J. M. Kahn^1
1E. L. Ginzton Laboratory, Department of Electrical Engineering, Stanford University, USA
²School of Electrical and Computer Engineering, University of Campinas, Brazil
We show by analysis and simulation of a multisection model that polarization- or mode-dependent gain from single-mode semiconductor optical amplifiers or multimode erbium-doped fiber amplifiers causes the channel capacity with minimum-mean-square error detection to become substantially lower than that of optimal maximum likelihood detection. However, the capacity loss can be mitigated with techniques such as successive interference cancellation (SIC) that retain reasonable complexity. We reaffirm that frequency diversity enables the outage capacity to approach the average capacity and evaluate the performance of frequency-domain SIC equalizers for single-carrier transmission on frequency-selective optical fiber channels operating at 64 Gbaud up to 15,000 km.
Keywords: channel capacity, nonlinear equalization methods, frequency diversity, modal diversity, ultra-long-haul optical communications.

Tsuyoshi Konishi
Spectroscopic inspection optimization for Edge computing in Industry 4.0
T. Konishi, T. Nakamichi, R. Kamikawa, and Y. Yamasaki
Osaka University, Japan
We discuss a new spectroscopic inspection approach from the viewpoint of edge computing in Industry 4.0.

Giuseppe Leo
Nonlinear dielectric metasurfaces with full field control
C. Gigli¹, G. Marino¹, C. De Angelis², and G. Leo^1
1Matériaux et Phénomènes Quantiques, Université de Paris, France
²Department of Information Engineering, University of Brescia, Italy
Optical metasurfaces, i.e. arrays of coupled optical antennas with sub-wavelength size and separation, have become very popular in the last decades. After their demonstration for flat optics in the linear regime, both with metallic and dielectric nanostructures, their nonlinear counterparts have also attracted an increasingly strong attention. While today optically amorphous metasurfaces provide spectacular waveform engineering of the harmonic field, their nonlinear generation efficiency is generally poor. Conversely, highly nonlinear metasurfaces based on non-centrosymmetric crystals don’t lend themselves naturally to a full control of the generated harmonic, due to non-intuitive design of the interacting near-fields that resonate in three dimensions at the nanoscale. In this presentation we will illustrate the different routes explored in the last two years, toward metasurfaces that combine efficient second harmonic generation and reliable control of its radiation pattern, polarization and phase front. Our main focus will be on the most performing nonlinear nanophotonics platform at telecom wavelengths to date, which is based on the bulk non-resonant χ⁽²⁾ of aluminium gallium arsenide.
Keywords: nonlinear photonics, nanophotonics, metasurfaces, second-harmonic generation, AlGaAs.

Yongcheng Li
Upgrading nodes with colorless, directionless, and/or contentionless ROADMs in an optical transport network
Yongcheng Li¹, Jingjing Li¹, Liangjia Zong², Sanjay K. Bose³, and Gangxiang Shen^1
1School of Electronic and Information Engineering, Soochow University, Suzhou, Jiangsu Province, China
²Transmission Technology Research Department, Huawei, Shenzhen, Guangdong Province, China
³Indian Institute of Technology Guwahati, India
Reconfigurable optical add/drop multiplexers (ROADMs) are critical for flexible lightpath establishment and release in an optical transport network. Today, a large number of colorless (C) ROADMs have been deployed in optical networks. However, with the maturity of colorless, directionless, and/or contentionless (CD/CDC) ROADMs, carriers start to upgrade their network nodes with these because of their more flexible lightpath reconfiguration capabilities. This therefore leads to the important problem of deciding the best strategy for RODAM node upgradation. In this paper, we explore this research problem and propose various strategies for ROADM node upgradation under dynamic lightpath traffic demands. Specifically, we consider how to upgrade nodes from C ROADMs to CD ROADMs and eventually to CDC ROADMs. We also evaluate the maximum benefit obtainable by deploying these more advanced ROADMs. Our simulation studies show that the proposed strategies are efficient in significantly improving lightpath blocking performance. We also find that CD ROADMs are cost-effective to achieve performance close to that of CDC ROADMs.
Keywords: ROADMs, colorless, directionless, contentionless, node upgradation.

Paolo Monti
Optical RL-Gym: An open-source toolkit for applying reinforcement learning in optical networks
C. Natalino and P. Monti
Chalmers University of Technology, Gothenburg, Sweden
Reinforcement Learning (RL) is leading to important breakthroughs in several areas (e.g., selfdriving vehicles, robotics, and network automation). Part of its success is due to the existence of toolkits (e.g., OpenAI Gym) to implement standard RL tasks. On the one hand, they allow for the quick implementation and testing of new ideas. On the other, these toolkits ensure easy reproducibility via quick and fair benchmarking. RL is also gaining traction in the optical networks research community, showing promising results while solving several use cases. However, there are many scenarios where the benefits of RL-based solutions remain still unclear. A possible reason for this is the steep learning curve required to tailor RL-based frameworks to each specific use case. This, in turn, might delay or even prevent the development of new ideas. This paper introduces the Optical Network Reinforcement-Learning-Gym (Optical RL-Gym), an open-source toolkit that can be used to apply RL to problems related to optical networks. The Optical RL-Gym follows the principles established by the OpenAI Gym, the de-facto standard for RL environments. Optical RL-Gym allows for the quick integration with existing RL agents, as well as the possibility to build upon several already available environments to implement and solve more elaborated use cases related to the optical networks research area. The capabilities and the benefits of the proposed toolkit are illustrated by using the Optical RL-Gym to solve two different service provisioning problems.
Keywords: machine learning, autonomous network management, resource assignment, reinforcement learning environments.

Vittorio Passaro
Parity-time and anti-parity-time-symmetry integrated optical gyroscopes: A perspective for high performance devices
V. M. N. Passaro¹, M. De Carlo¹, F. De Leonardis¹, G. Menduni¹, L. Lamberti², and A. G. Perri^3
1Photonics Research Group, Department of Electrical and Information Engineering, Politecnico di Bari, Italy
²Department of Mechanics, Mathematics and Management, Politecnico di Bari, Italy
³Electron Devices Laboratory, Department of Electrical and Information Engineering, Politecnico di Bari, Italy
It is well known that different optical techniques can be used to measure angular velocities. Interferometric Optical Gyroscopes (IFOGs) and Ring Laser Gyroscopes (RLG) exploit the Sagnac effect and are the preferred solutions for tactile grade applications. However, in the Sagnac effect the measured output is directly proportional to the gyroscope sizes. So, the miniaturization and the integration of optical gyroscopes is still a challenge in optoelectronics research. In this paper different approaches based on parity-time and anti-parity-time symmetry are explained and compared as highly performance solutions for the integration of optical gyroscopes. The sensitivity of the rotation-induced frequency-splitting (broadening) can be several orders of magnitude higher than the classical Sagnac splitting achieved with a single ring gyroscope occupying the same surface. We will show that anti-parity-time-symmetric solutions represent a better choice for angular velocity sensing.
Keywords: optical gyroscopes, coupled resonators, Sagnac effect, parity-time symmetry, anti-PT symmetry.

Pablo Pavón Mariño
Towards an open-source framework for jointly emulating control and data planes of disaggregated optical networks
I. Iglesias-Castreño, M. Garrich Alabarce, M. Hernández-Bastida, and P. Pavón Mariño
Universidad Politécnica de Cartagena, Spain
Software Defined Networking (SDN) principles in optical networks pursue disaggregated approaches, in which optical equipment is governed by the SDN controller with standard interfaces and common modelling abstractions. Software agents are a fundamental piece in disaggregated optical networks because they translate the commands from the SDN controller into specific actions to be performed by hardware equipment. In this paper, we rely on an existing framework for constructing software agents (Netopeer2-Sysrepo) and we discuss the common approach for the interaction between software agents and hardware equipment. Then, we report our preliminary advancements towards an optical emulation framework built on top of an automatic creation of agents. We use the OpenConfig-based model of Cassini and its ONOS driver, which are recent developments within TIP and ODTN initiatives, respectively.
Keywords: optical networks, SDN, SBI, NETCONF, software agents, Netopeer2.

Erwan Pincemin
A fully connected neural network approach to mitigate fiber nonlinear effects in 200G DP-16-QAM transmission system
C. Catanese¹, R. Ayassi¹, E. Pincemin¹, and Y. Jaouën^2
1Orange Labs, Lannion, France
²IMT Telecom ParisTech, Palaiseau, France
Advances in WDM transmission towards higher bit rate and denser spectral efficiency are challenged by fiber nonlinear effects. The existing digital signal processing techniques able to mitigate fiber nonlinear transmission impairments suffer from heavy computational resources and require the knowledge of a large number of system parameters, which is impractical in a field environment. By being agnostic to transmission parameters and driven only by data, neural networks offer a highly interesting solution. Here, a fully connected neural network is proposed for non-linearity mitigation in optical fibers. The proposed neural network, located after Carrier Phase Estimation algorithm at receiver side, performs a multivariate regression: its outputs are the real and imaginary parts of each symbol. Its aim is to find the inverse transfer function of the nonlinear transmission link. The proposed solution is trained and tested with a DP-16-QAM signal at 32GBaud in quasi-single channel propagation conditions, with simulated and experimental data. It allows a BER improvement over a large range of span input powers.

Stenio Ranzini
Optoelectronic signal processing for chromatic dispersion mitigation in direct detection systems
S. M. Ranzini^1,2, F. Da Ros¹, H. Bülow², and D. Zibar^1
1DTU Fotonik, Technical University of Denmark, Lyngby, Denmark
²Nokia Bell Labs, Stuttgart, Germany
An optical pre-processing structure is used to reduce the burden of digital equalizers and increase transmission reach for a direct detected system impaired by chromatic dispersion. The optical pre-processing consists of the optical signal being sliced into narrow frequency sub-band by an optical filter. Two distinct filters are numerically investigated: an arbitrary waveguide grating (AWG) filter and a series of cascaded Mach-Zehnder delay interferometers (MZDI). Each signal’s spectral slice is detected by a photodetector and used as input for the digital equalizer. Two options are also considered for equalization: a feedforward neural network (NN) equalizer and a recurrent neural network with reservoir computing (RC). The results are analyzed in simulation in terms of signal- to-noise penalty at the KP4 forward error correction threshold. The penalty is calculated with respect to a back-to- back transmission without equalization. A 32 GBd on-off transmission shows 0 dB penalty at ≈25 km transmission reach with optoelectronic processing with FNN and at ≈40 km with RC.
Keywords: reservoir computing, signal equalization, chromatic dispersion mitigation, short-reach transmission, direct-detection.

André Richter
Achievable mitigation of nonlinear phase noise through optimized blind carrier phase recovery
G. Di Rosa and A. Richter
VPIphotonics, Berlin, Germany
Partial mitigation of nonlinear phase noise by standard carrier phase recovery has been reported both, experimentally and through simulations. In this paper we quantify the achievable mitigation by using different implementations of the carrier phase recovery. All the approaches are based on the widespread blind phase search algorithm but follow different optimization strategies for handling simultaneously both, linear and nonlinear impairments of the channel. We apply the algorithms on probabilistically shaped signals transmitted over standard single mode fiber and non-zero dispersion shifted fiber in order to consider conditions in which the system performance is evidently affected by nonlinear phase noise. The results obtained are finally compared to the statistically estimated achievable phase noise removal. This allows to evaluate in different system scenarios an upper bound to the potential gain obtainable by algorithms developed to mitigate the detrimental impact of short-correlated nonlinear phase noise.

Gangxiang (Steven) Shen
Asymmetric CDC ROADM architecture for efficient support of bi-directional asymmetric traffic demands
Longjin Lu¹, Yongcheng Li¹, Liangjia Zong², B. Mukherjee¹, and Gangxiang Shen^1
1Suzhou Key Laboratory of Advanced Optical Communication Network Technology, Soochow University, Jiangsu Province, China
²Transmission Technology Research Department, Huawei, Shenzhen, Guangdong Province, China
The popularity of video-oriented applications causes increasing bi-directional asymmetry of traffic demands. We design a novel asymmetric CDC ROADM architecture to efficiently carry bi-directional asymmetric traffic demands, which can significantly reduce hardware cost compared to the conventional symmetric architecture.

Kestutis Staliunas
Gain-through-loss in nonlinear fibers: Modulation instabilities and tunable frequency combs
F. Bessin¹, A. M. Perego², K. Staliunas^3,4, S. Turitsyn^2,5, A. Kudlinski¹, M. Conforti¹, and A. Mussot^1
1Lille University, CNRS, France
²Aston University, Birmingham, UK
³ICREA, Barcelona, Spain
⁴UPC, Terrassa (Barcelona), Spain
⁵Novosibirsk State University, Russia
We propose a new counterintuitive mechanism of modulation instability: asymmetric, with respect to pump, losses can induce gain of sideband modes in absence of phase matching. The mechanism is experimentally demonstrated to generate frequency combs with tunable frequencies.

Weiqiang Sun
On dynamic hypervisor placement in virtualized software defined networks (vSDNs)
Sen Chen, Weiqiang Sun, and Weisheng Hu
State Key Laboratory of Advanced Optical Communications Systems and Networks, Shanghai Jiao Tong University, Shanghai, China
Virtual software defined networking networks (vSDNs) combines the benefits of software defined networking (SDN) and network virtualization, and is important to make effective use of physical network resources. In vSDN environments, the control plane latency is the sum of the two parts: the latency from switch to its hypervisor and the latency from hypervisor to controller. Therefore, in order to optimize the latency of the network, the location of hypervisors need to be carefully decided. In this paper, we study the placement strategy of hypervisors when the location of hypervisor may be changed in run time. We mainly have two goals: minimize the latency of switch to its controller and minimize the impact due to the hypervisor migration. We propose a general model called dynamic hypervisor placement problem (DHPP) to solve this problem. DHPP dynamically changes the hypervisors’ location and switches’ corresponding hypervisor to achieve trade-offs between latency metrics and hypervisor migration overhead. The model is formulated as an Integer Linear Problem (ILP). Our simulation results show that our solution minimizes the controller plane latency while incurring low hypervisor migration overhead.

Ioannis Tomkos
Challenges and opportunities towards 6G mobile networks
I. Tomkos, Athens Information Technology (AIT), Greece

Jan Vanda
High-energy ultra-short laser pulses transmission with optical fibers
P. Cech, M. Mydlar, M.-G. Muresan, J. Brajer, and J. Vanda
HiLASE Center, Institute of Physics CAS, Dolni Brezany, Czech Republic
Pulsed lasers with high peak power are commonly used in science and industry for a wide range of applications, from particle acceleration thru material treatment and machining towards communication and sensing. Due to the high intensity or fluence required in specific applications, beam distribution and delivery from the source towards treated or examined specimen becomes bottleneck limiting broader utilization of lasers. Conventional use of free-space optics is sufficient in laboratory environment and proof-of-principle experiments, but they are sensitive to contamination, space demanding and easily damaged. Using pulsed laser as a full-fledged tool requires more flexible and reliable means. In current study is described our approach in transmitting short and ultra-short laser pulses with peak powers exceeding 100 MW thru optical fibers. In addition, methods of laser induced damage mitigation, different approaches related with intended applications, currently developed solutions and future prospect for scaling up towards GW peak powers transmission will be discussed.

Stefan Wabnitz
Dynamics of high-energy multimode Raman solitons
M. Ferraro¹, M. Zitelli¹, F. Mangini², D. S. Kharenko³, A. Niang², and S. Wabnitz^1,3
1Department of Information Engineering, Electronics and Telecommunications (DIET), Sapienza University of Rome, Italy
²Department of Information Engineering (DII), University of Brescia, Italy
³Novosibirsk State University, Russia
The dynamics of high-energy Raman solitons in graded-index multimode fibers is both numerically and experimentally investigated. The propagation of high-power pulses produces nonlinear losses, that quench up to 80% of the fiber transmission. In such a regime, several solitons arising from the fission of ultra-short femtosecond pulses manifest unique features: pulse width, Raman self-frequency shift and soliton order remain nearly constant over a broad range of energies.
Keywords: optical solitons, optical fibers, Kerr effect, Raman scattering, ultrashort phenomena.

Ke Wang
Neural networks and FPGA hardware accelerators for millimeter-wave radio-over-fiber systems
Jeonghun Lee¹, Jiayuan He², and Ke Wang^1
1School of Engineering, Royal Melbourne Institute of Technology (RMIT University), Australia
²School of Computing and Information Systems, The University of Melbourne, Australia
High speed data streaming has been highly demanded by mobile end users and millimetre-wave (mm-wave) radio-over-fiber (RoF) optical communications have been studied to satisfy the users’ demands. To solve various impairments existing in mm-wave RoF systems, neural networks have been proposed and studied due to their capability in solving nonlinear effects and multiple impairments simultaneously. However, previous studies mainly focused on the fully-connected neural network (FC-NN), which has relatively complicated architecture and a large number of parameters to be learnt. To solve this issue, we have proposed the convolutional neural network (CNN) and binary convolutional neural network (BCNN) based decision schemes. In addition, the neural networks in previous studies are typically implemented offline using high-end CPUs or GPUs, which are not practical for optical communication applications. To solve this issue, we have proposed the field-programmable gate array (FPGA) based hardware accelerators, which have the key advantages of reconfigurability, low power consumption, and parallel computation capability. A novel inner parallel optimization method has also proposed to improve the latency with minimal additional power consumption. Results show that the CNN/BCNN implemented with GPU and with the FPGA-based hardware accelerator achieves similar BER performance within the forward-error-correction (FEC) limit, while the FPGA-based hardware accelerators reduce the power consumption significantly.
Keywords: millimeter-wave radio-over-fiber system, convolutional neural network, binary convolutional neural network, field programmable gate array, neural network hardware accelerator.

Xu Wang
Novel ultrafast imaging technology
Xu Wang, Heriot Watt University, Edinburgh, UK
We are developing ultrafast imaging technology using technologies we’ve developed for high-speed optical communication. Various data compressing techniques have been developed to enable the novel high speed imaging. Low cost 120 kfps ultrafast imaging system has been successfully demonstrated in the experiment.

Tianhua Xu
Influence of spectral broadening on nonlinearity compensation in ultra-wideband optical fibre communications
Tianhua Xu^1,2,3, Jiazheng Ding¹, Yifan Liu², Wenxiu Hu², B. Karanov^3,4, N. A. Shevchenko⁵, Zhe Li⁶, and Tiegen Liu^1
1Tianjin University, China
²University of Warwick, Coventry, UK
³University College London, UK
⁴Nokia Bell Labs, Stuttgart, Germany
⁵University of Cambridge, UK
⁶Finisar Corporation, California, USA
Optical fiber networks form the major part of the modern telecommunication infrastructure and are carrying over 95% of the Internet digital data. The increasing demand for higher data rates has promoted the development of higher-order modulation formats, denser wavelength multiplexing and more powerful signal processing. With the entire suppression of the chromatic dispersion, the polarization mode dispersion and the laser phase noise using digital signal processing, Kerr fiber nonlinearities become the main capacity barrier for optical communication systems, and digital back-propagation is generally applied to overcome such distortions. Kerr effects also result in the broadening of spectra of signals propagating in optical fibers, owing to intra- and inter-channel nonlinear interactions. This report shows that the spectral broadening effect is crucial for achieving an optimal performance of the digital back-propagation in wideband optical transmission systems.
Keywords: optical fiber communications, Kerr fiber nonlinearities, spectral broadening, digital back-propagation.

Xuelin Yang
Secure key generation and distribution using polarization dynamics in fiber
Liuming Zhang, A. A. E. Hajomer, Xuelin Yang, and Weisheng Hu
Shanghai Institute for Advanced Communication and Data Science, State Key Laboratory of Advanced Optical Communication Systems and Networks, Shanghai Jiao Tong University, China
Dynamic properties of optical signals in fiber channel provide a unique, random and reciprocal source for physical-layer secure key generation and distribution (SKGD). In this paper, an inherent physical-layer SKGD scheme is proposed and demonstrated, where the random source is originated from the dynamic fluctuation of the instant state of polarization (SOP) of optical signals in fiber. Due to the channel reciprocity, highly-correlated fluctuation of Stokes parameter of SOP is shared between the legal partners, where an error-free key generation rate (KGR) of 196-bit/s is successfully demonstrated over 25-km standard single-mode fiber (SSMF). In addition, an active polarization scrambler is deployed in fiber to increase the KGR, where an error-free KGR of 200-kbit/s is achieved.
Keywords: secure key generation, key distribution, state of polarization, Stokes parameter.

Yaping Zhang
DBR lasers with 10Gbps RF direct modulation
Yaping Zhang^1,2
1University of Nottingham Ningbo China, Ningbo, China
²Shandong OptoChip Optoelectronics Ltd, Jinan, China
This paper reports on the recent commercial product development on the 10 Gbps RF direct modulated Distributed Bragg Reflector (DBR) lasers, featuring 8 nm wavelength tuning range, 20 mW output power, high SMSR ratio (>40 dB), and high burn-in reliability performance. This development has paved the way towards low cost, reliable, and industrial standard high speed tunable lasers for 5G and metro network upgrading applications.

 

5GT invited presentations:

Sarvesh Bidkar
Low-latency TDM-PON for 5G fixed-mobile-convergence
S. Bidkar, Nokia Bell Labs, Stuttgart, Germany
As 5G networks gain momentum towards commercial deployments, existing fixed access network technologies such as the TDM-PON can provide an efficient, cost-effective transport option to carry radio signals between the radio units and centralized processing units of the 5G RAN architecture. However, the low-latency requirements of the mobile traffic, specifically for the fronthaul segment of the RAN are challenging to support with existing TDM-PON operations. In this paper, we present TDM-PON as a viable transport option for 5G RAN traffic and some of the techniques to support low-latency traffic with bandwidth efficiency.

Mirosław Klinkowski
Latency-aware flow allocation in 5G NGFI networks
M. Klinkowski¹ and D. Mroziński^2
1National Institute of Telecommunications, Warsaw, Poland
²Wroclaw University of Science and Technology, Wroclaw, Poland
The next generation fronthaul interface (NGFI) architecture has been proposed as a flexible and cost-effective solution developed for meeting stringent latency and high throughput requirements of future centralized and virtualized radio access networks (C-RAN/vRAN) in 5G mobile networks. In the NGFI network, the radio data to be processed is transmitted between a radio unit (RU), distributed unit (DU), and centralized unit (CU) by means of packets routed over a packet-switched transport network. In this paper, we focus on the latency-aware flow allocation (LFA) problem in the NGFI network, which concerns allocation of transmission resources for data flows assuming quality of service requirements related to maximal latency of these flows. To assess the network performance, we apply a meta-heuristic optimization algorithm and perform numerical experiments in a grid network topology connected using high capacity fiber links.
Keywords: 5G, NGFI, fronthaul network, packet-switched network, network optimization.

José Antonio Lázaro
Experimental assessment of NOMA-CAP waveforms for beyond 5G optical fronthaul applications
V. J. Narvaez¹, S. Sarmiento², J. A. Altabas³, D. Izquierdo⁴, A. Martinez⁵, C. Mas⁵, I. Garces⁶, J. B. Jensen³, A. Lerin², and J. A. Lazaro^1
1Universitat Politècnica de Catalunya, Barcelona, Spain
²Altran Innovación, Barcelona, Spain
³Bifrost Communications, Scion DTU, Lyngby, Denmark
⁴Centro Universitario de la Defensa, Academia General Militar, Zaragoza, Spain
⁵Chair of Communication Networks, Technical University of Munich, Germany
Aragon Institute of Engineering Research, University of Zaragoza, Spain
The constant growth of traffic demands caused by IoT, cloud computing and streaming services on personal devices, requires changes in architecture and more sophisticated schemes by pushing forward 5G optical fronthaul applications. An experimental assessment of NOMA CAP modulation is performed to foresee as technique for fronthaul setups concerning the 5G and beyond paradigms. NOMA CAP has been measured in scenarios with IM-DD systems. The transmitter is staged: on one side, a DML with a 1550 nm (VCSEL); on the other hand, an EML based on TLS and modulated by MZM. In addition, the receivers proposed are based on PIN (-13 dBm) and APD (-25 dBm) with a maximum data rate 14 Gbps over 50km of SSMF. Moreover, a practical approach for APD is validated with the comparison between the block (EDFA-Filter-PIN) and an SFP transceiver (APD included), the results in terms of sensitivity show a 0.1 dB to 0.5 dB difference.

Alberto Lometti
Fronthaul in 5G transport networks: IEEE1914.1 architecture and requirements
A. Lometti and V. Sestito
SM Optics, Vimercate, Italy
The deployment of 5G New Radio (NR) implies the capability both to deliver new mobile services (eMBB, URLLC, mMTC) and to perform critical functions as massive MIMO, beamforming, carrier aggregation, CoMP and scalable centralized/virtualized radio access network (C-RAN/V-RAN). In order to ease the implementation of such services and functions 3GPP specifies, from Release 14 onwards, functional split options for the baseband station processing chain, resulting in a separation between “distributed units” (DUs), located at cell sites, and Centralized Units (CUs), implementing the higher layer processing chain of several baseband units. Moving from 3GPP network view, the newly published IEEE Std 1914.1 specifies: - Architecture for the transport of mobile fronthaul traffic over packet-based networks (e.g. Ethernet); - Requirements and definitions for the fronthaul networks, including data rates, synchronization, and quality of service (QoS), for user data traffic, management and control plane traffic; - Models for the application of network slicing over fronthaul networks (“per QoS” and “per transport user”). In this paper we recap the basics of the new standard and focus on the fact that the relevant recommendations can be easily extended to a by far broader scope, including backhaul beside fronthaul services in the same transport infrastructure as well as any transport solution even if “not packet-based”. In this sense, it can be used as a general reference for the design and the analysis of carrier grade transport networks devoted to mobile cross-hauling applications. A practical example based on a TDM/WDM technology like OTN is used to validate the assumption.
Keywords: eCPRI (enhanced Common Public Radio Interface), NGFI (New Generation Fronthaul Interface), OTN (Optical Transport Network), RAN (Radio Access Network), RoE (Radio over Ethernet), TSN (Time Sensitive Networking), WDM (Wavelength Division Multiplexing).

Andrew Lord
Benefits of static and dynamic orchestration in 5G-driven optical networks
A. Lord¹, A. Rafel¹, and P. Pavon^2
1BT, UK
²UPCT, Spain
This talk will summarise the extensive Metro-Haul EU project, with focus on the architecture, including the optical backhaul. Various options for backhauling were considered, including options for both static and dynamic bandwidth provisioning. We will present the results of an extensive techno-economic modelling activity, designed to show the benefits of implementing a Control Plane capable of responding rapidly to changes in bandwidth requirements from future 5G applications. We will also describe some of the novel optical technology that will enable dynamic metro networks without the use of expensive ‘core network’ components.

Nelson Muga
DSP optimization for simplified coherent receivers
N. J. Muga¹, R. K. Patel^1,2, I. A. Alimi¹, N. A. Silva¹, and A. N. Pinto^1,2
1Instituto de Telecomunicações, University of Aveiro, Portugal
²Department of Electronics, Telecommunications, and Informatics, University of Aveiro, Portugal
The imminent 5G and data-center services and applications are imposing stringent requirements on the optical communication systems due to the ever-increasing network traffic. Based on this, there is significant need to enhance per wavelength data rate beyond 100 Gb/s. Meeting the current and future requirements for a high-speed system demands novel coding schemes, advanced modulation formats, and high-performance DSP algorithms. This paper presents our recent investigations on the optimization of the DSP subsystems for simplified coherent receivers, including the Kramers-Kronig scheme and the Stokes vector receiver architecture.
Keywords: digital-signal processing, Kramers-Kronig scheme, Stokes vector receiver, optical detection, self-coherent detection.

Carla Raffaelli
From IoT to cloud: Applications and performance of the MQTT protocol
D. Borsatti¹, W. Cerroni¹, F. Tonini², and C. Raffaelli^1
1DEI – University of Bologna, Italy
²Department of EE, Chalmers University of Technology, Gothenburg, Sweden
5G networking allows the Internet of Things (IoT) concept to span across access, edge and transport networks and reach cloud computing facilities. A cloud-based IoT testbed is presented with the description of the key role of the MQTT protocol and related performance.

Salvatore Spadaro
Autonomic 5G and beyond network management
S. Spadaro, F. Agraz, A. Pagès, and R. Montero
Optical Communications group (GCO), Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
This paper addresses the autonomic management of optical transport networks in support of 5G and beyond services. Firstly, a proper architecture design is presented, and then a practical use case exploiting such architecture is discussed, highlighting its benefits to guarantee the vertical requirements.

Carmen Vázquez
The role of power-over-fiber in C-RAN fronthauling towards 5G
D. S. Montero, J. D. López-Cardona, F. M. A. Al-Zubaidi, I. Pérez, P. C. Lallana, and C. Vázquez
Electronics Technology Department, Universidad Carlos III de Madrid, Leganés, Spain
We explore the potential integration of power-over-fiber (PoF) systems for the next generation 5G cloud radio access network front-haul solutions based on spatial division multiplexing with multicore fibers. Different architectures, including spatial division multiplexing with multicore fibers for both shared- and dedicated- core scenarios, are discussed. The PoF energy delivery to the remote site depending on the efficiencies of the different components and on fiber limitations is addressed as well as impairments related to non-linear effects, fiber crosstalk and temperature. The impact of high power-over-fiber signals on the data traffic signal quality is analysed. This study may help to design future power by light delivery added-value solutions for 5G Radio over Fiber systems and radio access networks with optical fronthauling.

ACCESS invited presentations:

Germán Arévalo
Direct-detection 25 Gb/s PON: PROs and CONs of digital signal processing at the transmitter side
P. Torres-Ferrera¹, M. Tipán¹, R. Gaudino¹, D. Cardenas², and G. V. Arévalo^3
1Politecnico di Torino, Dipartimento di Elettronica e Telecomunicazioni, Torino, Italy
²Escuela Politécnica Nacional, Quito, Ecuador
³Universidad Politécnica Salesiana, Quito, Ecuador
We evaluate the performance of direct-detection 25 Gb/s Passive Optical Networks (PON) with adaptive equalization at the receiver side, comparing three transmitter schemes: two including digital signal processing (DSP), namely square-root raised-cosine pulse shaping and pre-emphasis, and the third one without any DSP pre-compensation. We show that DSP at transmitter side can provide a performance advantage only under strong bandwidth limitations and when considering feed-forward equalization (FFE) at the receiver. When including decision-feedback equalization (DFE), the use of pre-compensation at transmitter does not provide any advantage under linear transmission. Keywords: PAM-4, pulse shaping, pre-emphasis, transmitter, pre-equalization, pre-compensation, PON, DSP.

Jose Manuel Delgado Mendinueta
NOMA-CAP modulation format for next generation converged fronthaul-optical access and data center interconnect networks
J. M. Delgado Mendinueta¹, S. Sarmiento^1,2, J. A. Altabás^3,4, S. Spadaro², S. Shinada¹, J. J. Vegas Olmos⁵, J. A. Lázaro², and H. Furukawa^1
1Photonic Network System Laboratory, National Institute of Information and Communications Technology (NICT), Koganei, Tokyo, Japan
²Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
³Bifrost Communications, Scion DTU, Lyngby, Denmark
⁴Aragon Institute of Eng. Research, Uni. of Zaragoza, Spain
⁵Mellanox Technologies, Yokneam, Israel
The ubiquitous use of video and gaming streaming applications in mobile and home devices is constantly increasing the traffic demand of optical access networks. In the future, emergent applications such as the internet of things and massive machine-to-machine communications may increase this demand even further. Moreover, the capacity demand in optical interconnects is also expected to grow steadily. Recently, we proposed the use of non-orthogonal multiple access-carrierless amplitude phase (NOMA-CAP) modulation format as a suitable candidate for future generation optical short reach networks, including optical access and interconnect networks. NOMA-CAP achieves high spectral efficiency, enables direct detection, exhibits a great degree of flexibility due to its multiband nature and has a reasonable computational complexity compared with competing modulation formats such as orthogonal frequency division multiplexing (OFDM). We first experimentally demonstrate NOMA-CAP as a modulation format for split-enabled optical interconnects with a capacity of up to 630 Gb/s using 7-core multi-core fiber (MCF) and requiring an electrical bandwidth of 25 GHz. Furthermore, we experimentally demonstrate a converged new-generation wireless radio over fiber (RoF) front-haul with a wired passive optical network (PON), consisting of a 15 Gb/s NOMA-CAP channel (wireless) coexisting with a legacy 10 Gb/s quaternary pulse amplitude modulation (PAM4) signal (wired).
Keywords: mobile fronthaul convergence, non-orthogonal multiple access (NOMA), carrierless amplitude phase (CAP), optical access networks, passive optical networks, optical interconnects.

Francesco Musumeci
Dynamic DU/CU placement for 3-layer C-RANs in optical metro-access networks
L. Askari, F. Musumeci, L. Salerno, O. Ayoub, and M. Tornatore
Politecnico di Milano, Italy
We investigate power-aware dynamic DU/CU placement for a 3-layer C-RAN architecture in optical metro-access networks. We show that adaptive placement and reconfiguration of both DU and CU locations based on traffic allows to significantly decrease energy consumption, paying off only a negligible increase in service blocking.

Anderson Sanches
Rate-flexible optical CDMA networks based on coherent modulation formats
A. Sanches¹, M. Abuhelala², T. R. Raddo¹, S. Haxha³, and I. Glesk^2
1Engineering, Modeling, and Applied Social Sciences Center, Federal University of ABC, Santo Andre, Brazil
²Faculty of Engineering, University of Strathclyde, Glasgow, UK
³Department of Electronic Engineering, Royal Holloway, University of London, UK
Coherent techniques in optical access networks might become a major paradigm shift since the introduction of fiber-optic communications due to recent advances in coherent optical technology. In this paper, we propose, design, and assess the performance of coherent access networks based on optical code-division multiple-access (OCDMA) considering three distinct coherent modulation formats, namely, binary phase-shift keying, quadrature phase-shift keying, and 16-quadrature amplitude modulation. We design a flexible network architecture based on these coherent modulation formats to provide either single rate transmissions or multiple data rate transmissions. In this way, the network supports rate-flexible services with all user classes transmitting at the same rate or classes of users transmitting at different data rates. We derive new closed-form bit error rate expressions to assess the performance of the rate-flexible coherent OCDMA network. Results shown that rate-flexible data traffic from different user classes can coexist almost transparently in terms of network performance. The rate-flexible OCDMA network might be a prospective alternative for implementing coherent access networks with modulation formats as a service according to different traffic demand requirements while supporting high capacity, security, and numbers of users.
Keywords: BPSK, QPSK, 16-QAM, coherent network, Bit Error Rate (BER), OCDMA.

 

BigNeO invited presentations:

Sima Barzegar
Soft-failure localization and time-dependent degradation detection for network diagnosis
S. Barzegar, M. Ruiz, and L. Velasco
Optical Communications Group (GCO), Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
In optical networks, degradation of the Quality of Transmission (QoT) can be the outcome of soft-failures in optical devices, like Optical Transponders, Wavelength Selective Switches (WSS) and Optical Amplifiers (OA). In this paper, we assume time-dependent degradations on ROADMs and OAs. Specifically, several degradations are considered: i) the noise figure can increase linearly over time due to the aging of the components; ii) the maximum of optical output power of the amplifiers can decrease because of the degradation in the pump lasers of the EDFAs; iii) aging effects, e.g., due to fiber splices; and iv) the OSNR can vary caused by frequency drift of WSSs due to temperature variations. Our proposal for degradation detection and soft-failure localization includes algorithms that are able to detect and localize the degradation in early stages and facilitate network diagnosis. In addition, we propose an architecture where the control plane consist of a network controller, a Monitoring and Data Analytics system and a QoT tool based on GNPy that are interconnected with each other.

Paola Festa
On the shortest path problems with edge constraints
D. Ferone¹, P. Festa², and T. Pastore^2
1Department of Mechanical, Energy and Management Engineering, University of Calabria, Rende, Italy
²Department of Mathematics and Applications “R. Caccioppoli”, University of Napoli FEDERICO II, Italy
The goal of this work is to provide a brief classification of some Shortest Path Problem (SPP) variants that include edge constraints and that find applications in several different contexts, including optical networks, transportation and logistics. One of the most broad and notable classes of edge-constrained SPPs is given by the so called Resource Constrained Shortest Path Problems (RCSPPs). In RCSPPs, in addition to the customary directed graph G = (V,E) and the edge-distance function, a L-dimensional vector of resources R is defined. Essentially, each resource is related to relevant link attributes that needs to be accounted in the planning of the path. Accordingly, a path P* is optimal whenever it is minimal w.r.t. the distance function, and satisfies the restrictions enforced on the resources. Other variants can involve colors assigned to the nodes or the edges of the graph and/or reload costs. This kind of problems have relevant applications in networks reliability. Particularly interesting is the so called k-Color SPP, where a color is assigned to each edge and the minimum path from a given source node s to a target node t must not cross more than k differently colored edges. As for the use of reload costs, a reload cost r(b,c) is assigned to each pair of colors (b,c) and represents the amount to be paid if in a path P an arc of color c is traversed after an arc of color b. In this paper, we formally define the most important edge-constrained SPPs and survey the most efficient state of the art algorithms to approach them.
Keywords: constrained shortest path problem, colored paths, network flow problems.

Lluis Gifre
Monitoring and data analytics-triggered reconfiguration in partially disaggregated optical networks
L. Gifre¹, F. Boitier¹, C. Delezoide¹, M. Ruiz², M. Buffa³, A. Morea³, R. Casellas⁴, L. Velasco², and P. Layec^1
1Nokia Bell Labs, Nozay, France
²Optical Communications Group (GCO), Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
³Nokia, Vimercate, Italy
⁴Centre Tecnològic Telecomunicacions Catalunya (CTTC), Castelldefels, Spain
Nowadays, the telecom industry is moving from fixed infrastructures to reprogrammable hardware. Software Defined Network (SDN) controllers centralizes control and management of network devices and provides unified management interfaces for network operators. Besides, novel Monitoring and Data Analytics (MDA) techniques can be used to take appropriate decisions to reconfigure network components, thus reducing margins, CAPEX and OPEX, while improving network reliability and performance. Optical network disaggregation aims at improving the agility and cost efficiency of multi-vendor optical networks. Nevertheless, open device agents are needed to (dis)aggregate network components and expose meaningful network devices to the SDN controller. In this paper, we propose ADONIS, a novel open device agent able to construct virtual network devices from logical (dis)aggregation of physical components. We demonstrate ADONIS in a control closed-loop involving an SDN controller, an MDA system, and a planning tool.
Keywords: autonomic networking, monitoring and data analytics.

João Pedro
Performance comparison of operational strategies for media channel provisioning with dynamic margin management
J. Pedro^1,2, D. Moniz^1,2, and J. Pires^2
1Infinera Unipessoal Lda, Carnaxide, Portugal
²Instituto de Telecomunicações, Instituto Superior Técnico, Lisboa, Portugal
Real-time monitoring of optical performance has been shown to enable hardware savings by operating the transport network closer to the performance limits. Despite this, most studies forgo operational considerations, such as the procedures to be enforced when an active media channel (MCh) is too close to the performance limit and it is no longer acceptable to use it in the present configuration. Importantly, the operational strategies that can be adopted to perform this task are dependent on factors such as the transport node architecture and the service level agreement (SLA). Hence, this work describes three main strategies to exploit dynamic margin management in a transport network, comparing their performance over reference networks in terms of key metrics such as the extent of hardware savings and the number of, potentially traffic affecting, rerouting events.

Marc Ruiz
End-to-end KPI analysis in converged fixed-mobile networks
M. Ruiz¹, M. Richart², A. Castro², and L. Velasco^1
1Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
²Universidad de la República, Montevideo, Uruguay
The independent operation of mobile and fixed network segments is one of the main barriers that prevent improving the network performance, while reducing capital expenditures coming from overprovisioning. In particular, a coordinated dynamic network operation of both network segments is essential to guarantee end-to-end Key Performance Indicators (KPI), on which new network services relay on. To achieve such dynamic operation, accurate estimation of end-to-end KPIs is needed for autonomic networking purposes such as triggering network reconfiguration before performance degrades. In this paper, we present extensions of the CURSA-SQ methodology to achieve accurate, scalable and predictive estimation of end-to-end KPIs with sub-second granularity near real-time in converged fixed-mobile networks. CURSA-SQ combines simulation and machine learning fueled with real network monitoring data. Numerical results validate the accuracy, robustness, and usability of the proposed CURSA-SQ methodology for converged fixed-mobile network scenarios.

Fatemehsadat Tabatabaeimehr
Distributed knowledge management process for collective self-learning in optical networks
F. Tabatabaeimehr, M. Ruiz, and L. Velasco
Optical Communications Group (GCO), Universitat Politècnica de Catalunya, Barcelona, Spain
Although autonomic networking have been experimentally demonstrated, their application in real networks entails some challenges that are not yet solved; particularly that of the availability of complete datasets that can be used for ML training, as many datasets are collected from simulation and/or lab experiments and might not cover real deployments. To overcome this issue, complex knowledge management architectures towards practical and effective implementation of autonomous control loops are being recently proposed. In this paper, we present several methods for knowledge sharing and knowledge assimilation based on the distribution and combination of ML models that are initially trained in distributed nodes. Two illustrative use cases based on classical optical network ML applications are used to evaluate the proposed algorithms. Exhaustive simulation results validate the proposed methodology as enabler for collective self-learning in optical networks.
Keywords: knowledge sharing and assimilating, machine Learning, network automation, self-learning.

Juan Jose Vegas Olmos
Big data processing and artificial intelligence at the network edge
J. J. Vegas Olmos¹, F. Cugini², F. Buining³, N. O’ Mahony⁴, T. Truong⁴, L. Liss¹, T. Oved¹, Z. Binshtock¹, and D. Goldenberg^1
1Mellanox Technologies, Yokneam, Israel
²Conzorcio Nazionale Interuniversitario per le Telecommunicazione (CNIT), National Lab of Photonic Networks, Pisa, Italy
³Hiro MicroDataCenter, Voorburg, The Netherlands
The delivery of computing services - including storage, databases, networking, software, analytics, intelligence and more is moving from the cloud towards the edge; among all technical requirements, the edge needs to be able to natively support artificial intelligence processes to enable new technological paradigms, such as smart Factory 4.0, healthcare assisted living, smart cities and advanced robotics, for example. In this paper, we will present the enabling technologies to will be developed within the “Big data processing and artificial intelligence at the network edge” (BRAINE) project, one of the largest joint activities in Europe in the area of edge computing enabling artificial intelligence. BRAINE covers the full stack of a system solution, from subsystem integration up to artificial intelligence service provisioning, and includes four use cases of direct impact in the European ecosystem.
Keywords: edge computing, artificial intelligence, computing infrastructure, extreme scale analytics.

Luis Velasco
Knowledge management in optical networks
L. Velasco, F. Tabatabaeimehr, and M. Ruiz
Optical Communications Group (GCO), Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
Autonomous network operation realized by means of control loops, where prediction from machine learning (ML) models is used as input to proactively reconfigure individual optical devices or the whole optical network, has been recently proposed to minimize human intervention. A general issue in this approach is the limited accuracy of ML models due to the lack of real data for training the models. Although the training dataset can be complemented with data from lab experiments and simulation, it is probable that once in operation, events not considered during the training phase appear thus leading into model inaccuracies. A feasible solution is to implement self-learning approaches, where model inaccuracies are used to re-train the models in the field and to spread such data for training models being used for devices of the same type in other nodes in the network. In this paper, we develop the concept of collective self-learning aiming at improving models error convergence time, as well as at minimizing the amount of data being shared and stored. To this end, we propose a knowledge management (KM) process and an architecture to support it.
Keywords: knowledge management; network automation; autonomic transmission; self-learning.

 

CTS invited presentations:

Noureddine Boudriga
Multi-array spherical LIDAR system for drone detection
M. Salhi and N. Boudriga
CNAS, Supcom, University of Carthage, Tunisia
The detection of unmanned aerial vehicles (UAVs) represents a necessity to protect critical areas and infrastructures against potential attacks performed by these UAVs. Different detection solutions have been proposed in the literature. They include conventional radars, radio frequency signal detection, acoustic detection, as well as light detection and ranging (Lidar) using cameras. Using cameras, the latter technology is new and promising, yet controversial for its feasibility and cost effectiveness. In this paper, we propose a multi-array Lidar system that is capable of detecting potential UAVs using visible light communication. The system is composed of laser sources and laser concentrators. These transmitting/receiving elements are arranged through arrays along a spherical form including a photodiode at its center. The reflected optical energy reaching the concentrators is transmitted to this central photodiode. The work assesses the feasibility and effectiveness of the solution through an in-depth examination of the design parameters. This includes the sensors’ characteristics, the elements positioning and interspace, as well as the dimensions of the monitored spherical cylinder.

Jordi Casademont
Multi-radio V2X communications interoperability through a multi-access edge computing (MEC)
J. Casademont^1,2, B. Cordero², D. Camps-Mur², L. A. Morais da Conceição³, C. Laoudias⁴, and A. Lalos^5,6
1Universitat Politècnica de Catalunya, Barcelona, Spain
²i2CAT, Barcelona, Spain
³Ubiwhere, Aveiro, Portugal
⁴University of Cyprus, Nicosia, Cyprus
⁵University of Patras, Rio, Patras, Greece
⁶ATHENA Research Centre, Patras, Greece
The ecosystem of connected vehicles and Cooperative Intelligent Transport Systems (C-ITS) has been working in developing standards, building prototypes and deploying real testbeds for more than ten years. Now, it is time to start the industrialization phase and to deliver final products to the consumers. The C-ITS system's upper layer protocols (from network layer and up) are stable and, although there are two main architectures, the European based on the GeoNetworking protocol standardized by ETSI and the North-American based on the WAVE (Wireless Access in Vehicular Environments) architecture standardized by IEEE, there is no much problem because each one will be used in specific regions and it is not foreseen to have areas with vehicles using both architectures. The main controversy is in the Physical and Link layers which contain the radio technologies to be used around the world, independently on which upper layer protocols are. Nowadays, there are two main lines of technologies, both with one working standard and a new version in development. The more mature is IEEE 802.11p and later it came the proposal from 3GPP which is LTE-V2X Release 14. While these two technologies are commercially fighting to get chosen by the vehicle industry, they are working on the new standards IEEE 802.11bd and 5G NR-V2X. The fact is that, as for early 2020, some vehicles manufacturers, as Volkswagen, have begun to distribute vehicles with IEEE 802.11p and shortly, there will be other cars equipped with LTE-V2X. This raises the problem that vehicles using different radio technologies will not be able to communicate directly between them. Apart from having vehicles equipped with multiple technologies, the solution is to relay on functions performed by the fixed network and have communications V2I2V (Vehicle-to-Infrastructure-to-Vehicle). Nevertheless, due to the strict end-to-end delay restrictions required by some C-ITS applications, it seems that the use of a Multi-access Edge Computing (MEC) could provide the necessary performance values. This paper provides a presentation of the four different V2X radio technologies and the possible architectures of fixed network using a MEC that will make interoperability between vehicles using different radio technologies possible. Moreover, taking advantage that the MEC is already foreseen in the architecture, we will propose other functionalities that can additionally be performed by the MEC as filtering frames to be relayed on the basis of their region of influence using GeoNetworking protocol headers, dropping messages if their security certificates have expired, providing support for safety applications and executing other new security functions as detecting misbehaviours on the broadcasted position of the vehicles. Finally, we will present the approach taken by the ongoing H2020 CARAMEL project which deals with these issues and plans to implement a testbed with 802.11p Road Side Units (RSU), LTE Small Cells and their interoperation through a MEC with the cited extended functions.

Joan García-Haro
Advisory speed estimation for an improved V2X communications awareness in winding roads
J. Aznar-Poveda, E. Egea-López, A.-J. Garcia-Sanchez, and J. Garcia-Haro
Department of Information and Communication Technologies, Universidad Politécnica de Cartagena (UPCT), ETSIT, Cartagena, Spain
The European Telecommunications Standards Institute (ETSI) establishes a Decentralized Congestion Control (DCC) which triggers the so-called Cooperative Awareness Message (CAM) depending on vehicle kinematics. However, this algorithm hence called CAM-DCC represents a challenge in the triggering rules of these messages. In particular, it lacks (i) awareness of the neighboring vehicles and (ii) efficient use of the channel bandwidth. Consequently, information gaps related to the road environment might give rise to non-compliances in the application layer requirements of the vehicles, which could potentially threaten the drivers’ safety, most particularly in hazardous roads. To overcome these flaws, we first study the CAM generation trigger focused on the vehicle heading in risky curves or winding roads. Then, we evaluate both scenarios tuning different triggering thresholds and including additional mechanisms such as the comparison of the current speed respect to the estimated advisory speed over time. Different computer simulations have been conducted in two real road sections to validate our proposal. Results reveal significant better performance in terms of awareness and channel usage.
Keywords: vehicular networks, cooperative awareness message, rate control, winding and curved roads, congestion, awareness.

Ivan Glesk
2-D optical-CDMA modulation in automotive time-of-flight LIDAR systems
Wing C. Kwong¹, Wei-Yi Lin², Guu-Chang Yang², and I. Glesk^3
1Department of Engineering, Hofstra University, Hempstead, NY, USA
²Department of Electrical Engineering and Graduate Institute of Communication Engineering, National Chung Hsing University, Taichung, Taiwan
³Center for Intelligent and Dynamic Communications, Electronic and Electrical Engineering Department, University of Strathclyde, Glasgow, UK
In this paper, the application of 2-D optical code-division multiple-access (OCDMA) modulation using wavelength-hopping time-spreading codes in long-range automotive time-of-flight (ToF) light detection and ranging (LIDAR) systems is proposed and demonstrated. The regulations and constraints that govern the design of the proposed system are presented. Using 2-D carrier-hopping prime codes, the modulation technique and associated hardware are implemented and validated with OptiSystem simulation. Interference-robustness studies show that the proposed 2-D OCDMA ToF LIDAR system is more flexible in the choice of system/code parameters and can support many more sensors and simultaneous ToF measurements than the 1-D counterpart.

Kira Kastell
Comparison of suitable infrastructure for different transportation scenarios with focus on cars
K. Kastell, Fachhochschule Frankfurt am Main – University of Applied Sciences, Germany
In this paper different transportation scenarios focusing on cars are described. These contain rural and urban scenarios with different degrees of autonomy as well as different external entities contributing information, e.g. traffic lights. The scenarios are analyzed with respect to their requirements. The resulting parameters are checked against IEEE 802.11p, WAVE IEEE 1609, and 5G. From there a suitable infrastructure for each scenario is described.

Tetsuya Kawanishi
Simple pedestrian detection secondary radar using frequency doubling
T. Kawanishi^1,2, S. Masuda¹, E. Shigematsu¹, K. Jitsuno¹, K. Inagaki^1,2, and A. Kanno^2
1Waseda University, Shinjuku, Tokyo, Japan
²National Institute of Information and Communications Technology (NICT), Koganei, Tokyo, Japan
This paper describes a secondary radar for detection of hidden pedestrians. A transponder carried by a pedestrian responds to a radio-wave transmitted from a car. The distance between the transponder and the car can be measured by using a phase detection scheme, where the frequency detected radio-wave is doubled at the receiver.

Alicia López
Experimental characterization of the transmission properties of large-core graded-index PMMA fibers
A. López, N. Villar, A. Losada, E. Laporta, and J. Mateo
Photonics Technology Group (GTF), Aragón Institute of Engineering Research (i3A), Universidad de Zaragoza, Spain
Large-core PMMA graded-index plastic optical fibers (GI-POF) share the advantages of standard step-index PMMA fibers (SI-POF) along with a much lower modal dispersion that leads to a much higher transmission capacity even for very long links. In fact, the limits of this capacity have not been clearly determined as the measurement of the fiber frequency response is challenged by the lack of sources and photodetectors with the required bandwidth. In addition, the non-constant index profile of GI-POF affects light coupling at the fiber ends that further impacts the fiber transmission properties, so that input/output light coupling conditions have to be carefully considered in this type of fibers. In this work, we have performed a complete experimental characterization of the transmission properties of PMMA GI-POF. We have used a high bandwidth photodetector to measure the frequency response of the fiber as a function of its length. Also, attenuation and angular intensity distribution have been included in the study. The final goal is to gain a better understanding of the behavior and the transmission properties of PMMA GI-POF exploring the mechanisms involved in light propagation through these fibers.
Keywords: plastic optical fibers, experimental characterization, optical communications.

Samael Sarmiento
Study of graphene-SOI-based micro-ring resonator for beamforming automotive radars
S. Sarmiento^1,2, J. A. Lazaro², A. Lopez³, M. A. Losada³, J. Pinazo¹, and A. Lerin^1
1Altran Innovación, Barcelona, Spain
²Universitat Politècnica de Catalunya, Barcelona, Spain
³Aragon Institute of Engineering Research, University of Zaragoza, Spain
The development of autonomous vehicles has generated a need for, among others, improving detection and ranging accuracy. Beamforming radars based on electrical solutions are relevant as they can allow informative 4-dimensional (4-D) measurements. However, their bandwidth is limited due to the beam squint. To resolve this problem, optical delay lines (ODLs) based on micro-ring resonators (MMRs) are a promising solution. In this paper, we study the MMR as key ODL building block for future self-driving vehicles requiring radar-based sensing. To allow for continuous delay tuning, MMR based on graphene-silicon waveguide structure is considered. Results show that, for an MMR radius of 20 µm, the delay can be tuned in a range of 10 ps for a voltage range of the graphene of 0.1 V, providing a flat delay range of 1.5 GHz.
Keywords: graphene, micro-ring resonator, optical delay line, radar, self-driving vehicle, silicon-on-insulator waveguide.

Sergey Sokolov
Computer networking for management information system of unmanned vehicles
S. М. Sokolov and A. A. Boguslavsky
Keldysh Institute of Applied Mathematics Russian Academy of Sciences (KIAM RAS), Moscow, Russia
The ever-increasing need for the large-scale implementation of unmanned vehicles requires situational awareness of such vehicles. In this case two general directions are possible. The first: simplification and fixing situations with vehicles movements. The second: improving the onboard control system and its information component. We focus on the second direction in our study. Information support of vehicles, especially systems of technical vision, requires ever-increasing computing resources and intelligent technologies in algorithmic support. The experience of our research shows that reconfigurable high-performance heterogeneous resources are the effective software and hardware tool for information support of autonomous vehicles Such devices combine sequentially parallel processing of visual data. In the process of developing such resources, we use a heterogeneous computer network based on the PCI express bus. The report describes the general scheme of such a network, considers hardware and software configurations for solving application task, gives the results of experiments to solve the issues of collecting and processing visual data, and discusses the prospects for the development of this approach.
Keywords: intelligent technologies, neural network architectures, tensor processors, serial-parallel processing, unmanned vehicles.

Naoaki Yamanaka
Cyber-physical system for autonomous driving vehicle considering with social welfare
N. Yamanaka¹, G. Yamamoto¹, S. Okamoto¹, and A. Fumagalli^2
1Department of Information and Computer Science, Keio University, Japan
²University of Texas at Dallas, USA
Autonomous driving vehicle control network by edge computer having very short response time has been constructed. Each vehicle has an agent program on the edge and communicated with adjacent vehicle. The advantage of connected vehicle control from stand-alone vehicle is sophisticated and total/global control. The network edge computer calculated “social welfare” which is benefit for all vehicle. This paper describes control architecture and method at edge computer. In addition, some experimental results for controlling autonomous vehicle are also described.

 

DACINT invited presentations:

Nikos Bamiedakis
A new equalizer structure for high-speed optical links based on carrierless amplitude and phase modulation
N. Bamiedakis, Xiaohe Dong, D. G. Cunningham, R. V. Penty, and I. H. White
Centre for Photonic Systems, Department of Engineering, University of Cambridge, UK
The ever increasing data traffic inside data centres is pushing the demand for high-speed short-reach optical links. Currently, 400 Gb/s links are under development. In order to achieve this target, the use of advanced modulation formats is essential in order to mitigate the limited bandwidth of the optical and electrical components in such links. Carrierless amplitude and phase modulation (CAP) is an attractive passband modulation scheme that offers increased spectral efficiency over conventional on-off keying (OOK), removes baseline wander and allows simple implementation that can achieved with digital circuits. It relies on the transmission of two orthogonal pulses which form a Hilbert transform pair and which can be perfectly separated at the received side provided that the magnitude of the frequency response of the link is flat and its phase response is linear. In real systems however, this is not the case resulting in intersymbol (ISI) and channel crosstalk interference (CCI) which severely impairs the performance of the link. In this work therefore, we present a new equalizer structure that mitigates such transmission impairments in CAP-based links and which can easily implemented using hardware. The principle of operation of this new equalizer, named CAP equalizer, is presented and its use in a VCSEL-based 112 Gb/s CAP-16 OM4 MMF link is studied via both simulations and experiments. It is shown that the link employing the CAP equalizer outperforms the same link using a conventional FFE and DFE equalizer of the same total length and the respective links employing pulse amplitude (PAM) and discrete multitone (DMT) modulation. This equalizer structure can enable practical implementation of single-lane VCSEL-based 100 Gb/s OM4 links.

Dieter Bimberg
910 nm single-mode VCSELs and its application for few-mode transmission over graded-index single-mode fibers
G. Larisch¹, A. A. Juarez², Xin Chen², Kangmei Li², D. Bimberg^1,3, and Ming-Jun Li^2
1Bimberg Chinese-German Center for Green Photonics of Chinese Academy of Science at CIOMP, Changchun, China
² Corning Incorporated, Corning, NY, USA
³ Center of Nanophotonics, Institute of Solid-State Physics, Technische Universität Berlin, Germany
Short distance optical communication in data centers has been dominated until now by multimode-fiber links based on multimode vertical cavity surface emitting lasers (VCSELs). Their large wall-plug and energy efficiency, as well as the relaxed requirements for fiber connectivity, reduces the overall cost of the system. A single-mode (SM) VCSEL has lower NA and smaller spot size making it suitable for coupling the light into the standard single-mode fiber. We show that a SM VCSEL can be implemented at 910 nm with high bandwidth (> 25 GHz) and high side mode suppression ratio (> 40 dB) at wavelengths beyond 850 nm to add more capacity for SM VCSEL transmission. The performance of the 910 nm SM VCSEL is evaluated at 25 Gbit/s using two single mode graded index fibers. These fibers are single mode at 1310 nm and 1550 nm, enabling their use for long-reach and high bandwidth applications, while still providing enough bandwidth for short wavelength, short-reach, and cost sensitive applications. Error free (BER < 10^-13) data transmission of 25 Gbit/s across 1 km is achieved using a 910 nm optimized fiber and 150 m transmission using a fiber optimized for dual wavelength (850 nm and 910 nm) transmission.
Keywords: single mode VCSELs, graded-index single-mode fiber.

Roberto Gaudino
Experimental demonstration of coherent transmission over MMF and of the impact of connectors offset
G. Rizzelli¹, A. Nespola², S. Straullu², G. Giannuzzi¹, A. Carena¹, F. Forghieri³, and R. Gaudino^1
1Politecnico di Torino, Italy
²LINKS Foundation, Torino, Italy
³Cisco Photonics Italy S.r.l., Vimercate, Italy
Ever since their installation intra-data center interconnects have extensively employed multimode fibers for distances up to 300 m as they enable the use of simple, low-cost VCSEL technology in the transceivers. However, modal dispersion sets a limit to the maximum achievable transmission rate at such distances, making communication at speeds above 50 Gbit/s impractical. Extending the work presented in [1–3] we present here an experimental proof of concept of coherent transmission over multimode fibers using PM-QPSK modulation. Through experiments validated by a numerical model based on [4] we also evaluate the power penalty introduced by the offset launch induced by the connectors at the interface between two multimode fibers or between multimode and single mode fibers. We demonstrate 32 Gbaud PM-QPSK coherent transmission over 296 m of multimode OM3 fiber, showing that when central launch is applied an extremely high power budget of 33 dB can be obtained, which would also allow to tolerate a power loss of several dB, making the system more robust to the offset launch-related performance degradation.
[1] M. Kim, B. G. Kim, H. Kim and Y. C. Chung, “Transmission of 56-Gb/s PAM-4 signal over 2.3 km of MMF using mode-field matched center-launching technique,” in Opto-Electronics and Communications Conference/Photonics Global Conference, (IEEE 2017), pp. 1-2.
[2] Z. Wu et al., “Experimental demonstration of MMF fundamental-mode MMF transmission enabled by mode conversion,” in Asia Communications and Photonics Conference, 2017.
[3] Y. Ma, Y. Tang and W. Shieh, “107 Gb/s transmission over multimode fiber with coherent optical OFDM using center launching technique,” in European Conference on Optical Communication, 2009.
[4] A. Amphawan et al., “Derivation of an analytical expression for the power coupling coefficient for offset launch into multimode fiber,” IEEE J. Lightwave Technol. vol. 28, pp. 861-869, 2010.

Aleksandra Kaszubowska-Anandarajah
200 Gb/s short reach transmitters based on optical frequency combs
S. T. Ahmad¹, P. D. Lakshmijayasimha¹, P. M. Anandarajah¹, and A. Kaszubowska- Anandarajah^2
1Photonics Systems and Sensing Lab., School of Electronic Engineering, Dublin City University, Ireland
²CONNECT Research Centre, Dunlop Oriel House, Trinity College Dublin, Ireland
The authors demonstrate the use of an active demultiplexer, based on an optical injection locking technique, to demultiplex the individual comb tones. Furthermore, we show that the same device can also fulfil the role of an optical amplifier and a modulator. Experimental demonstration of the multiple functionalities of the proposed active demultiplexer, which include filtering, amplification and data modulation, all using a single device is presented.
Keywords: optical frequency comb, de-multiplexing, direct modulation, external modulation, injection locking, optical amplifier.

Chun-Nien Liu
Next generation of 1.6-Tbps optical transceiver module for high speed data center and cloud network
Chun-Nien Liu¹, Hsien Wu², Tien-Tsorng Shih², and Wood-Hi Cheng^1
1Graduate Institute of Optoelectronic Engineering, National Chung Hsing University, Taichung, Taiwan
²Department of Electronic Engineering, National Kaohsiung University of Applied Sciences, Taiwan
In this study, a next generation of 1.6-Tbps optical transceiver based on silicon photonics (SiPh) technology is demonstrated and presented. It integrates an optical engine, a V-groove with arrayed single-mode fibers, arrayed micro-lens, temperature controller, and assembled by chip-on-board (COB) fabrication. The high-power distributed feedback laser diodes (DFB LDs) were used as light sources and the laser wavelength range was from 1270 nm to 1330 nm. The data rate of the transceiver module is operated at 100Gbps four-level pulse amplitude modulation (PAM-4) electrical signal for a single channel transmission and 16-channels of 1.6-Tbps optical transceiver. We proposed hybrid assembly technique and modularized solution can meet high-density and high-speed I/O interconnection packaging requirements for silicon photonics device development and also can be applied in the next-generation optical transceivers for high-speed data centers and cloud networks.
Keywords: silicon photonics, optical transceiver, 100 Gbps PAM-4.

Oskars Ozolins
300 Gbps short-reach C-band optical links
O. Ozolins^1,2, Lu Zhang³, A. Udalcovs¹, H. Louchet⁴, T. Dippon⁴, M. Gruen⁴, Xiaodan Pang^2,1,5, R. Schatz², U. Westergren², Shilin Xiao⁶, S. Popov², and Jiajia Chen^7
1RISE Research Institutes of Sweden AB, Kista, Sweden
²KTH Royal Institute of Technology, Kista, Sweden
³Zhejiang University, Hangzhou, China
⁴Keysight Technologies GmbH, Böblingen, Germany
⁵Infinera, Stockholm, Sweden
⁶Shanghai Jiao Tong University, Shanghai, China
⁷Chalmers University of Technology, Gothenburg, Sweden
Exchange of information in fast, reliable and secure way with access anywhere is a must for a modern society. This leads to emerging traffic in Data Centers imposing tight requirements for short-reach optical links [1]. Research activities around next generation GbE interfaces requires wavelength division multiplexing (WDM) for short-reach optical links. Therefore C-band for intensity modulation direct detection (IMDD) short-reach optical communications is even more attractive [2]. In this talk we review experimental intensity modulation and direct detection demonstrations for short reach optical links. Furthermore, we evaluate 330-Gbps line rate with 128 quadrature amplitude modulation (QAM) discrete multitone (DMT) [3] and 300 Gbps line rate with 100 Gbaud 8-level pulse amplitude modulation (PAM8) [4] IMDD transmission after 400 meters below pre-forward error correction (FEC) bit error rate (BER) with a single packaged externally modulated laser (EML), a DAC and a packaged InP photo-detector (PD) in C-band [5].
[1] O. Ozolins, et al., “Multilevel modulation at 100 Gbaud for short reach C-band links,” in Proc. ICTON 2019, invited paper Th.D3.1
[2] O. Ozolins, et al., “100 GHz externally modulated laser for optical interconnects,” J. Lightwave Technol., 35(6), 1174-1179 (2017)
[3] L. Zhang, et al., “Lattice pilot aided DMT transmission for optical interconnects achieving 5.82-bits/Hz per lane” in Proc. ECOC 2019, paper Tu.3.D
[4] O. Ozolins, et al., “100 Gbaud PAM4 link without EDFA and post-equalization for optical interconnects” in Proc. ECOC 2019, paper Th.2.A
[5] O. Ozolins, et al., “300+ Gbps short-reach optical communications,” in Proc. CLEO 2020, invited paper We.3.A

Giuseppe Rizzelli
Two-fiber self-homodyne transmission for short-reach coherent optical communications
G. Rizzelli¹, A. Nespola², S. Straullu², F. Forghieri³, and R. Gaudino^1
1Dipartimento di Elettronica e Telecomunicazioni, Politecnico di Torino, Italy
²LINKS Foundation, Torino, Italy
³Cisco Photonics Italy S.r.l., Vimercate, Italy
Short-reach networks (<10 km) are today facing the challenge to upgrade their capacity per wavelength beyond 100 Gb/s/λ to support the growing traffic demand [1], for inter- and intra- data center applications. To date, mainly cost and complexity have prevented coherent detection from being extensively employed in short reach applications [2]. Recently, Morsy-Osman et al. [3] proposed a two-fiber self-homodyne solution based on coherent detection for intra-datacenter high-speed communication without local oscillator laser, showing that it can greatly reduce power consumption and transceiver complexity. In this paper, we extend the analysis of [2], [3] by focusing on the use of DFB lasers as a low-cost alternative to traditional narrow linewidth external cavity lasers. After characterizing the linewidths of commercial DFB and ECL lasers through the coherent delayed self-heterodyne (CDSH) method [4] for short optical path differences in the range of a few meters, we measure the BER performance as a function of the path difference of a self-homodyne system based on PM-QPSK and PM-16QAM modulation. Our findings show that the two-fiber self-homodyne approach enables the use of DFB lasers which introduce a 1 dB sensitivity penalty when the path difference is 2 m and 0.5 m for PM-QPSK and 16-QAM modulation respectively.
[1] The Optical Internetworking Forum, “Flex coherent DWDM transmission framework document,” (2017) [Online].
[2] J. K. Perin, A. Shastri and J. M. Kahn, “DSP-free coherent-lite transceiver for next generation single wavelength optical intra-datacenter interconnects,” Opt. Express 26, 8890-8903 (2018).
[3] M. Morsy-Osman, M. Sowailem, E. El-Fiky, T. Goodwill, T. Hoang, S. Lessard and D. V. Plant, “Design of low-power DSP-free coherent receivers for data center links,” IEEE J. Lightwave Technol. 35, 4650-4662 (2017).
[4] K. Kikuchi and K. Igarashi, “Characterization of semiconductor-laser phase noise with digital coherent receivers,” in Optical Fiber Communication Conference/National Fiber Optic Engineers Conference, paper OML3, (2011).

Ken-ichi Sato
Design and performance of large port count optical switches for intra data center application
Ken-ichi Sato, Nagoya University, Japan
The presentation discusses the design and performance of large port count optical switches based on silicon photonics technologies to create optical-circuit/electrical-packet hybrid switching systems for data center application. Optical switch scalability, which depends on various parameters such as bit rate, modulation format, and optical component loss, is analyzed. It verifies the low control latency and ultra-low blocking probability of optical switches made possible with the optical switch parallelism that matches the trend in merchant silicon switch chip advances together with a distributed control mechanism. The substantial reductions in power consumption, number of fiber links and transceivers are also presented.

Michela Svaluto Moreolo
Photonic transceiver and connectivity evolution: The future at terabit speed
M. Svaluto Moreolo, L. Nadal, and J. M. Fabrega
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Castelldefels (Barcelona), Spain
To follow the connectivity evolution towards a much more dense, complex, diverse and integrated scenario, optical networks have to support a myriad of new services and applications, standing in need of huge capacity/speed as well as instant data access. This translates in a set of challenging requirements including software and hardware aspects. The design of programmable transceivers targeting multi-Tb/s speed assumes a key role, particularly for the metro/aggregation network segment and distributed data center interconnection. On one hand, the target is providing flexibility, programmability and interoperability in the context of an ever more open and disaggregated paradigm. On the other hand, a reduction of cost, power consumption and footprint should be addressed, exploring and exploiting cost-effective photonic devices and photonic integration. In this invited talk, multi-dimensional transceiver architectures envisioned for enabling future connectivity will be presented, considering design, implementation, cost and programmability aspects.

 

DCN invited presentations:

Yun Chung
Practical multiplexing techniques for next-generation data center network
S. H. Bae, B. G. Kim, M. S. Kim, and Y. C. Chung
Korea Advanced Institute of Science and Technology, Daejeon, Korea
We report on the practical multiplexing techniques applicable to the next-generation ultrahigh-speed data center networks. In particular, we evaluate the feasibility of doubling the transmission capacity of the short-haul direct-detection system cost-effectively by utilizing the optical-time-division-multiplexing (OTDM) and mode-group-division-multiplexing (MGDM) techniques.
Keywords: data center network, short-haul transmission system, optical-time-division-multiplexing (OTDM), mode-group-division-multiplexing (MGDM).

António Eira
Metro transport network design for reliable service provisioning in edge data-centers
A. Eira and J. Pedro
Infinera Portugal, Amadora, Portugal
Joint dimensioning of optical and data-center infrastructures has become commonplace with the popularity surge of edge computing. While metro optical transport is traditionally characterized by a strongly cost-driven design, the concurrent optimization of data-centers’ location and size brings about the need for increased flexibility in the optical layer. This issue is intensified by stringent service reliability requirements that entail additional resources on both the optical and IT layers. This work analyzes the potentialities of metro optical node architectures in providing the needed capacity and reliability for optimized data-center dimensioning, by introducing an optimization framework that accounts for the total cost balance between optical interfaces and data-center resources for different node architecture models.

Jaafar Elmirghani
VM placement over WDM-TDM AWGR PON based data centre architecture
A. E. A. Eltraify, S. H. Mohamed, and J. M.H. Elmirghani
School of Electronic and Electrical Engineering, University of Leeds, UK
Passive optical networks (PON) can play a vital role in data centres and access fog solutions, by providing scalable, cost and energy efficient architectures. This paper proposes a Mixed Integer Linear Programming (MILP) model to optimise the placement of virtual machines (VM) over an energy efficient WDM/TDM AWGR PON based data centre architecture. The use of VMs affects the number of servers utilised in data centres hence lowering the power consumption and enabling more efficient utilisation of servers. Power efficiency optimisation is compared using different numbers of VMs which are efficiently mapped to servers. Traffic between servers is generated randomly using a uniform distribution up to 10 Gbps.
Keywords: passive optical networks, PON, WDM, TDM, VM, AWGR.

Stephan Pachnicke
Experimental demonstration of nonlinearity compensation by using SVM and nonlinear Volterra equalizer for 80 GBd DP-16-QAM transmission
R. Weixer, J. Koch, S. Ohlendorf, and S. Pachnicke
Christian-Albrechts-University of Kiel, Germany
We propose support-vector machine (SVM) based detection and nonlinear Volterra equalization applied to a data center interconnect link. Among the various algorithms for machine learning an SVM can provide a more powerful way of learning nonlinear functions. With the use of suitable kernel functions, the SVM is able to reduce errors caused by nonlinear phase noise (NLPN), laser phase noise, IQ imbalances, etc. For an 80GBd DP-16QAM modulated signal the SVM shows robustness against IQ-imbalances up to 43°-phase mismatch.
Keywords: digital signal processing, coherent detection, support vector machines, nonlinear Volterra equalization, SVM based detection.

Emmanouel Varvarigos
Network slicing and workload placement in megacities
P. Soumplis^1,2, P. Kokkinos^1,3, D. Lagos^1,2, A. Kretsis^1,2, V. Sourlas¹, and E. Varvarigos^1,2
1Institute of Communication and Computer Systems (ICCS-NTUA), Athens, Greece
²School of Electrical and Computer Engineering, National Technical University of Athens, Greece
³Department of Digital Systems, University of Peloponnese
The number and size of megacities and their respective networking and computing infrastructures constantly increases, while a large part of the network traffic originates and terminates locally. In such a dense and heterogeneous environment, network slices are formed, utilizing various optical networking infrastructures that carry data from end users to distributed, intra-city edge computing units, in which applications’ workload is appropriately offloaded. In our work, we examine mechanisms for the joint resource allocation and the applications’ workload placement in the access and metro network segments.
Keywords: network slicing, optical networks, edge resources, application workload placement.

 

D-Photon invited presentations:

Costantino De Angelis
Tunable filters for visible light based on resonant VO₂ planar thin films
D. de Ceglia¹, M. Grande², A. Vincenti^3,4, and C. De Angelis^3,4
1Dipartimento di Ingegneria dell’Informazione, University of Padova, Italy
²Dipartimento di Ingegneria Elettrica e dell’Informazione, Politecnico di Bari, Italy
³Dipartimento di Ingegneria dell’Informazione, University of Brescia, Italy
⁴National Institute of Optics (INO), Italy
Vanadium dioxide is a phase change material that undergoes an abrupt insulator-to-metal phase transition when its temperature is raised above 68°C. When the temperature is reduced, the structure reversibly switches back to the insulating phase. Since the transition is reversible over many cycles and it occurs by using different stimuli, i.e. thermal, electrical and optical, VO₂ is currently receiving attention for the development of novel, tunable photonic devices. A number of designs have been proposed, including planar thin-film resonators, nanoantennas and metasurfaces. In the solutions proposed so far, tunability is usually achieved by exploiting the large change of absorption coefficient in the infrared and at lower frequencies. Here we propose a Salisbury-screen configuration based on a mirror-backed VO₂ thin-film geometry, which works in the visible range and hence it relies on the change of VO₂ refractive-index rather than its absorption coefficient. The structure is designed to support a critical-coupling resonant condition with nearly-perfect absorption in a narrow band and it acts as a tunable filter for visible light under the application of a stimulus. We will discuss design strategies that optimizes the performances of the filter in terms of modulation depth and its possible implementations with currently available fabrication techniques.

Alessandro Massaro
Agri-photonics in precision agriculture
A. Massaro, N. Savino, and A. Galiano
Dyrecta Lab srl, Conversano (BA), Italy
Optical and photonic technologies are adopted to measure crop health and agri-food quality using remote sensing data in the visible, near-infrared, and thermal-infrared wavebands. Agri-Photonics represents a new branch of research including electronic and opto-electronic technological advances implemented on unmanned aerial vehicle (UAV), decision support systems (DSS), multispectral imaging, and precision agriculture sensing. The work proposes an overview of Agri-Photonics tools adopted in research projects, by focusing the attention on electronic implementation and on experimental bio-physics aspects.

Giancarlo Righini
Flexible photonics: Where are we now?
G. C. Righini^1,2, A. Szczurek^3,4, J. Krzak³, A. Lukowiak⁵, M. Ferrari^4,1, S. Varas⁴, and A. Chiasera^4
1Centro di Studi e Ricerche Enrico Fermi, Roma, Italy
²IFAC-CNR, MIPLAB Laboratory, Sesto Fiorentino, Italy
³Wroclaw University of Science and Technology, Poland
⁴IFN-CNR CSMFO Lab. and FBK Photonics Unit, Trento, Italy
⁵Institute of Low Temperature and Structure Research, PAS, Wroclaw, Poland
The growing success of printed, flexible, wearable electronics (with an expected market over $40 billion in 2020) has opened the way to the development of flexible photonics. An overview of the very recent advances in the design and realization of flexible photonic circuits and devices based on optical fibers and planar guided-wave structures is presented.

Elena Romanova
Multimode chalcogenide fibre based platform for the mid-IR evanescent wave spectroscopy of liquids
E. Romanova¹, S. Korsakova¹, and V. Shiryaev^2
1Saratov State University, Saratov, Russia
²Institute of Chemistry of High Purity Substances of RAS, Nizhny Novgorod, Russia
Development of distant real-time analysis of substances content by means of the fiber-based evanescent wave mid-IR spectroscopy encounters many problems such as fragility of few-mode chalcogenide fibers with sub-wavelength-size core, limited power density of radiation in the few-mode fibers, large coupling losses between sensing elements and the few-mode fibers. Using of multimode chalcogenide fibers provide a solution that is discussed in this paper. Examples of numerical characterisation of multimode fibers prove their suitability for combined functionalities as sensing elements and nonlinear frequency converters in the fiber-based sensors.
Keywords: fiber-based evanescent wave spectroscopy, mid-infrared, chalcogenide fibers, non-linear optics, supercontinuum generation.

 

ESPC invited presentations:

Romuald Houdré
Doubly resonant GaN photonic crystal cavity for second harmonic generation
Jun Wang¹, M. Clementi², M. Minkov³, J.-F. Carlin¹, A. Barone², M. Galli², D. Gerace², N. Grandjean¹, and R. Houdré^1
1Institut de Physique, Faculté des Sciences de Base, EPFL, Lausanne, Switzerland
²Dipartimento di Fisica, Università degli Studi di Pavia, Italy
³Department of Electrical Engineering, Stanford University, USA
We will report on experimental results on the generation of second harmonic in the visible range achieved with a doubly resonant structure between a heterostructure cavity mode and a bound state in the continuum.

 

Fibre Lasers invited presentations:

Juan Diego Ania-Castañon
Real-time characterization of ultra-long harmonically mode-locked femtosecond fibre lasers
J. D. Ania-Castañón¹, F. Gallazzi², J. Nuño³, C. Pulido¹, I. Cáceres-Pablo¹, and P. Corredera^1
1Instituto de Óptica “Daza de Valdés”, CSIC, Madrid, Spain
²Photonics Laboratory, Tampere University, Finland
³Department of Electronics, Universidad de Alcalá de Henares, Spain
Among the available technologies for ultrashort pulse generation, mode-locked fibre oscillators stand out as simple and inexpensive solutions, albeit limited in terms of power and thus restricted in their fields of exploitation unless paired with additional amplification and compression stages. We recently demonstrated the possibility of overcoming this limitation by reporting on a new kind of passive ultrafast harmonically mode-locked ultra-long ring fibre relying on InN-based semiconductor saturable absorber mirrors and few-km cavities based on conventional telecommunications fibre. These lasers, emitting at 1560 nm, were shown to achieve stable operation with pulse widths below 250 fs, repetition rates under 100 kHz and pulse energies above 200 nJ. As we will see, ultra-long pulsed sources such as these can be extremely versatile, allowing for dynamic switching between harmonic modes. Using the time-stretch Dispersive Fourier Transform, we provide here a real time picture of the spectral dynamics corresponding to the different available regimes of operation and present examples of potential applications for these new sources.

Sonia Boscolo
Striking nonlinear dynamics of mode-locked fibre lasers
Junsong Peng¹, S. Boscolo², Zihan Zhao¹, and Heping Zheng^1
1State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, China
²Aston Institute of Photonic Technologies, Aston University, Birmingham, UK
The use of real-time measurement techniques has enabled the observation of various remarkable nonlinear phenomena in mode-locked fibre lasers. In this talk, we review our recent results and advances in the area. We report on the multiple nonlinear processes involved in the build-up of dissipative solitons and soliton molecules, the generation of breathing dissipative solitons and breather molecules, the dynamics of soliton molecules in the normal-dispersion regime of a laser cavity, a conceptually new type of soliton explosions and the formation of rogue waves induced by soliton collision, and explosions of breathing dissipative solitons. Our experimental findings are corroborated by numerical simulations of the laser model and contribute to the fundamental understanding of complex nonlinear wave dynamics relevant to a large variety of physical systems.

Peter Dragic
Power scaling of diffraction-limited, narrow-linewidth fiber lasers to beyond 10 kW
P. Dragic¹, N. Yu¹, G. Pan¹, B. Meehan², M. Tuggle², M. Cavillon³, T. Hawkins², and J. Ballato^2
1Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, USA
²Center for Optical Materials Science and Engineering Technologies (COMSET) and the Department of Materials Science and Engineering, Clemson University, USA
³Institut de Chimie Moléculaire et des Matériaux d’Orsay (ICMMO), Université Paris-Sud, Université Paris-Saclay, CNRS, Orsay, France
Power scaling of near-diffraction-limited fiber lasers to the multi-kW level, especially with narrow linewidth, requires the suppression of a wide range of parasitic phenomena. This includes deleterious processes such as stimulated Brillouin and Raman scattering, which originate from nonlinear interactions with hypersonic and optical phonons, respectively. Transverse mode instability, an obstacle to maintaining good beam quality at high power, stems from the thermo-optic effect. Furthermore, as power scales, so too does the thermal load on the active fiber, necessitating more effectual removal of heat from the system. Finally, the fiber must be resistant to long-term photo-induced degradation. Approaches to managing these deleterious processes at high power are discussed, including targeted glass design used to optimize the magnitude of those material coefficients that drive these limitations.

John Dudley
Real time measurements of spectral instabilities in ultrafast fibre laser systems
C. Lapre¹, F. Meng¹, C. Billet¹, P.-A. Lacourt¹, T. Sylvestre¹, C. Finot², P. Ryczkowski³, G. Genty³, and J. M. Dudley^1
1Institut FEMTO-ST, Université Bourgogne Franche-Comté CNRS UMR 6174, Besançon, France
²Laboratoire Interdisciplinaire Carnot de Bourgogne, Université Bourgogne Franche-Comté CNRS UMR 6303, Dijon, France
³Photonics Laboratory, Tampere University, Tampere, Finland
Ultrafast mode-locked fibre lasers display a rich landscape of complex interaction dynamics due to the interplay of nonlinearity, dispersion and dissipation. Here, we use the Dispersive Fourier Transform technique to characterize a range of instabilities in a dissipative soliton fibre laser in a regime where both conventional soliton and similariton propagation play significant roles in the intracavity pulse shaping. Specifically, we perform real-time spectral measurements of stable single pulses, phase evolution of bound state molecules, and a new regime of intermittent instability and explosion dynamics. We also present results from numerical modelling that show very good qualitative agreement with experiment.

Mario Falconi
600 nm-wide band ASE optical source exploiting a Tm:Er:Yb:Ho co-doped germanate fiber
M. C. Falconi¹, A. M. Loconsole¹, V. Portosi¹, S. Taccheo^2,3, and F. Prudenzano^1
1Department of Electrical and Information Engineering, Politecnico di Bari, Italy
²Laser Group, Swansea University, UK
³Department of Electronics and Telecommunications, Politecnico di Torino, Italy
In this paper, the numerical model of a 980-nm pumped optical fiber source exploiting the amplified spontaneous emission (ASE) phenomenon is presented. The device is based on a Tm:Er:Yb:Ho co-doped germanate fiber [1-4] and allows incoherent light emission in the 1500-2100 nm wavelength range. The model exploits a rate equation approach [4-7] and considers the energy transfer phenomena between different rare earths. The particle swarm optimization (PSO) algorithm is applied in order to maximize the overall output power of the ASE noise. By employing a 53 cm-long optical fiber, with an input pump power of 0.5 W, an ASE spectrum covering a band of about 600 nm with a total output power of over 106 mW is obtained.
[1] A. Albalawi, M. Kochanowicz, J. Zmojda, P. Miluski, D. Dorosz, and S. Taccheo, "Fluorescence spectrum of an Yb:Er:Tm:Ho doped germanate glass," in Laser Congress 2018 (ASSL), OSA Technical Digest, paper ATu2A.4, Boston, 4-8 Nov. 2018.
[2] M. C. Falconi, D. Laneve, V. Portosi, S. Taccheo, and F. Prudenzano, “Design of ultra-wideband Yb:Er:Tm:Ho co-doped germanate glass devices,” 2019 21th International Conference on Transparent Optical Networks (ICTON) , Angers, 9-13 Jul. 2019, pp. 1-6.
[3] M. C. Falconi, D. Laneve, V. Portosi, S. Taccheo, and F. Prudenzano, “Modeling of a 980-nm pumped Yb:Er:Tm:Ho co-doped glass device for homogeneous gain and lasing over a 600-nm wavelength interval,” in Laser Congress 2019 (ASSL, LAC, LS&C), OSA Technical Digest, paper JTu3A.31, Vienna, Austria, 29 Sep.-3 Oct. 2019.
[4] M. C. Falconi, D. Laneve, V. Portosi, S. Taccheo and F. Prudenzano, “Design of a multi-wavelength fiber laser based on Tm:Er:Yb:Ho co-doped germanate glass,” Journal of Lightwave Technology, 2020. Accepted for publication, DOI: 10.1109/JLT.2020.2966999.
[5] M. C. Falconi, G. Palma, F. Starecki, V. Nazabal, J. Troles, S. Taccheo, M. Ferrari, and F. Prudenzano, “Design of an efficient pumping scheme for mid-IR Dy³⁺:Ga₅Ge₂₀Sb₁₀S₆₅ PCF fiber laser,” Photonics Technology Letters, vol. 28, no. 18, pp. 1984-1987, Sep. 2016.
[6] M. C. Falconi, G. Palma, F. Starecki, V. Nazabal, J. Trolès, J.-L. Adam, S. Taccheo, M. Ferrari, and F. Prudenzano, "Dysprosium-doped chalcogenide master oscillator power amplifier (MOPA) for mid-IR emission," Journal of Lightwave Technology, vol. 35, no. 2, pp. 265-273, Jan. 2017.
[7] M. C. Falconi, D. Laneve, M. Bozzetti, T. T. Fernandez, G. Galzerano, and F. Prudenzano, “Design of an efficient pulsed Dy³⁺:ZBLAN fiber laser operating in gain switching regime,” Journal of Lightwave Technology, vol. 36, no. 23, pp. 5327-5333, Dec. 2018.

Ori Henderson-Sapir
Mid-infrared Er³⁺:ZBLAN waveguide using ZBLAN glass extrusion, femto-second inscription and dual-wavelength pumping for the generation of 3.5 µm lasing
O. Henderson-Sapir^1,2, S. Oladipupo Fashola³, N. Bawden¹, A. Dowler¹, A. Ng¹, D. J. Ottaway¹, A. Fuerbach³, and H. Ebendorf-Heidepriem^1
1Department of Physics and Institute of Photonics and Advanced Sensing, The University of Adelaide, Australia
²Mirage Photonics, Oaklands Park, Australia; 3MQ Photonics, Department of Physics and Astronomy, Faculty of Science and Engineering, Macquarie University, North Ryde, Australia
In recent years, femto-second laser inscribed waveguide lasers have been shown to operate effectively in the near infrared as a hybrid form utilising the best of both fibre and solid-state crystal-based lasers. Here we present our work towards a 3.5 µm Er³⁺:ZBLAN femto-second laser inscribed waveguide laser. The waveguide was made by extruding bulk ZBLAN glass into a slab for the first time, to the best of our knowledge. The slab was then cut and polished with multiple concentric-ring waveguides of 28-36 µm core diameter written into the glass along its long axis resulting with a 125mm long waveguides embedded within a glass rectangle of 7x10x125mm. The waveguide structures are pumped by two single mode pump sources at 976nm and 1973nm employing the dual-wavelength pumping method for obtaining 3.5 µm operation. Numerical analysis of the system will be presented as well as our latest experimental results.

Jan Mrázek
Nanocrystalline ceramic luminophores for short- and mid-infrared
J. Mrázek, P. Vařák, J. Aubrecht, S. Vytykáčová, Y. Baravets, and I. Kašík
Institute of Photonics and Electronics of the Czech Academy of Sciences, Prague, Czech Republic
A great scientific effort has been dedicated to increase the fiber lasers power and to shift their operating wavelengths from traditional telecommunication range 1.2 -1.7 µm to longer wavelengths. The breakthroughs in many fields; such a LIDARs, chemical sensors, etc.; are associated with an existence of high-power lasers operating in the infrared range 2 -5 µm. Although the results in the field of chalcogenide or fluoride glass have opened new horizons, the thermal and chemical stability of such class of materials significantly limit the overall transmitted power and their applicability. Transparent ceramics may face this challenge because of their high thermal and chemical stability, low phonon energy and high transparency in short- and mid-infrared. We present the preparation of transparent ceramic luminophores based on rare earth doped pyrochlore ceramic emitting within the spectral range 2-3 µm. The effects of the nanocrystal size and composition of prepared materials on their optical properties will be evaluated and their possible application in planar amplifiers and fiber lasers will be presented.

Ahmed Nady
Multi-state solitons in multi-wavelength Er-doped fiber laser
A. Nady^1,2, M. Kemel¹, G. Semaan¹, M. Salhi¹, and F. Sanchez^1
1Laboratoire de Photonique d’Angers E.A 4464, Université d’Angers, France
²Physics Department, Faculty of Science, Beni-Suef University, Egypt
We report on the emission of composite-state solitons from a multi-wavelength mode-locked Er-doped fiber laser based on nonlinear polarization rotation (NPR) technique. The optical spectrum exhibits three distinct well-separated spectral peaks centred at 1567 nm, 1585 nm, and 1616 nm. It is mainly attributed to the linear losses and the nonlinear birefringence filtering inside the cavity. Each wavelength in the spectrum contributes by its own soliton dynamics to a composite-state soliton regime. This is verified by using an external optical tunable filter with 0.05 nm filter bandwidth to resolve the lasing at each wavelength. By controlling the cavity parameters, this regime still can be operated in harmonic states.

Pere Perez-Millan
Ultrafast fiber lasers in multiphoton science
P. Pérez-Millán, S. Torres-Peiró, H. Muñoz-Marco, and A. Almagro-Ruiz
FYLA LASER SL, Valencia, Spain
Originally predicted by Nobel Prize laureate Goeppert-Mayer in 1931, the multiphoton excitation (MPE) of materials has been exploited in a variety of applications that have given form to the discipline of Multiphoton Science. Examples of these applications range from the rather mature MPE microscopy for bioimaging, to more recently proposed techniques like Two Photon Absorption - Transient Current Technique, TPA-TCT, for spatially resolved inspection of semiconductors. Efficient MPE requires peak powers of tens to hundreds of kW. Thus, to avoid thermal damage of the samples, duration of pulses has to be as short as possible, typically in the range of tens to hundreds of femtoseconds. The Ti:Sa solid state laser is the current standard optical source of such type of pulses. Nevertheless, fiber laser technology has evolved in the last years towards the ability to emit pulses of duration down to tens of femtoseconds, particularly thanks to all-fiber Chirped Pulsed Amplification (CPA) schemes that take advantage of particular nonlinear and dispersion properties of microstructured optical fibers of different types. In this presentation the architectures and functionalities of all-fiber femtosecond lasers designed for multiphoton science applications will be discussed. Sources of 1.0 µm and 1.5 µm wavelengths, of pulse durations as short as 15 fs have been developed for these purposes. Their performance as excitation source in MPE microscopy and TPA-TCT, respectively, will be discussed.

Sergey Sergeyev
Polarization dynamics of coupled Raman lasers
S. Kolpakov^1,2, S. V. Sergeyev², A. Udalcovs³, X. Pang⁴, O. Ozolins^3,4, R. Schatz³, and S. Popov^3
1BARU, SSRI, Duke University, Durham, NC, USA
²Aston Institute of Photonics Technologies, Aston University, Birmingham, UK
³KTH Royal Institute of Technology, Kista, Sweden
⁴RISE Research Institutes of Sweden, Kista, Sweden
For coupled linear cavity-random fiber Raman lasers, here for the first time we demonstrate experimentally a new mechanism of emergence of the random pulses with the anomalous statistics satisfying rogue waves’ criteria. The rogue waves appears at nanosecond time scale as a result of coupling of two Raman cascades, namely linear cavity laser with the wavelength of 1550 nm and random laser with wavelengths nearby 1670 nm, along with coupling of the orthogonal states of polarization (SOPs). The coherent coupling of SOPs causes localization of the trajectories in the vicinity of these states whereas polarization instability drives escape taking the form of chaotic oscillations. Antiphase dynamics in two cascades results in cleansing of low amplitude chaotic oscillations and enabling the anomalous spikes satisfying rogue waves criteria.

Sergey Sergeyev
Polarization dynamics of mode-locked fiber laser
S. V. Sergeyev, H. Kbashi, and V. Sharma
Aston Institute of Photonics Technologies, Aston University, Birmingham, UK
By using a new vector model of Erbium-doped fiber laser with mode-locking mechanism based on nonlinear polarization rotation, we demonstrate for the first time a transition from a stable mode-locking with a locked state of polarization (SOP) to unstable mode-locking with periodically and chaotically evolving SOP. The chaotically evolving SOP corresponds to the intermittent behavior of the pulse energy (alteration between chaotic and laminar phase regimes) similar to the experimentally observed.

Sławomir Sujecki
Fluoride fibre lasers operating at wavelengths near 3 micrometres
L. Sojka¹, L. Pajewski¹, S. Sujecki^1,2, T. M. Benson², A. B. Seddon², M. Farries^2,3, S. Lamrini⁴, and K. Scholle^4
1Department of Telecommunications and Teleinformatics, Faculty of Electronics, Wroclaw University of Science and Technology, Poland
²George Green Institute for Electromagnetics Research, The University of Nottingham, UK
³Gooch & Housego Ltd., Somerset, UK
⁴LISA Laser Products GmbH, Katlenburg-Lindau, Germany
Lanthanide ion doped fluoride glass fibre lasers are very promising sources of high output power continuous wave light beams and high energy and peak power light pulses for the 3000 nm wavelength range. Due to strong absorption of light by water at 3000 nm wavelength, one of the potential application for lanthanide ion doped fluoride glass fibre lasers is fibre laser medical surgery. To date, fluoride fibre based lasers with operating wavelengths from 2800 nm up to almost 4000 nm have been realised. The dopants used include erbium, dysprosium and holmium. In this contribution a discussion of design and practical realisation of dysprosium ion and erbium ion doped fluoride fibre lasers is given. The discussion is supported by the presentation of experimentally and numerically obtained results.

 

FiWiN5G invited presentations:

Luca Chiaraviglio
A heuristic approach for the design of UAV-based disaster relief in optical metro networks
E. Cardoso¹, A. Souto¹, R. Alfaia¹, J. Araújo¹, R. Francês¹, C. Natalino², P. Monti², and L. Chiaraviglio^3
1Federal University of Para, Brazil
²Chalmers University of Technology, Sweden
³University of Rome Tor Vergata, Italy
Metropolitan optical networks are subject to disasters that may disrupt a substantial portion of the infrastructure, hindering the functioning of important services. Strengthening the network for these (rare) events, if possible, requires the deployment of costly and fixed equipment which usually remains idle in the absence of disasters. Recently, unmanned aerial vehicles (UAVs) have been successfully used to support several network use-cases. In this paper, we propose the use of UAVs and an intelligent re-routing strategy to partially or fully recover the network traffic disrupted by a disaster. Our algorithm is able to select appropriate optical nodes to receive optical-wireless interfaces that allow new wireless links to be added to the network after a disaster. The UAVs act as wireless aerial bridges and can be deployed quickly and effectively whenever a disaster is experienced. Results show that the proposed design is effective while reducing the cost when compared to a naïve design.

Lei Guo
VNE2: A virtual network embedding framework based on equivalent bandwidth in fiber-wireless enhanced 5G networks
Pengchao Han¹, Lei Guo², and Yejun Liu^2
1School of Computer Science and Engineering, Northeastern University, China
²School of Communication and Information Engineering, Chongqing University of Posts and Telecommunications, China
Fiber-Wireless (FiWi) enhanced 5G networks have gained a lot of popularity due to its advantageous anytime-anywhere access for end users with high bandwidth capacity and long distance. The scheduling and allocation of the heterogeneous resources in FiWi can be tackled through network virtualization. However, existing works on End-To-End (ETE) Quality of Service (QoS) guarantee of Virtual Network Embedding (VNE) ignore the random nature of network traffics, leading to non-negligible queuing delay. Moreover, the flexibility of resource allocation for link embedding is also ignored by constraining the same amount of allocated resources for all links on each physical path. In this paper, we highlight flexible and delay-guaranteed VNE design in FiWi enhanced 5G networks and propose a VNE framework based on Equivalent bandwidth (VNE2). The equivalent bandwidth is defined as a set of resources to be allocated to physical links on the path that a virtual link is embedded while guaranteeing ETE QoS. Furthermore, in order to bring the superiority of flexible resource allocation into full play, diversity of the amount of resources in the equivalent bandwidth for each virtual link is allowed to maximize Infrastructure Provider (InP) profit. Simulation results demonstrate that VNE2 can improve network performance in aspects of InP profit, virtual network acceptance ratio and ETE delay.
Keywords: fiber-wireless, 5G, virtual network embedding, equivalent bandwidth.

Dimitrios Klonidis
Joint spatial and spectral resource optimization over both wireless and optical fronthaul domains of 5G Architectures
T. D. Lagkas¹, D. Klonidis², P. Sarigiannidis³, and I. Tomkos^4
1Department of Computer Science, International Hellenic University, Kavala Campus, Greece
²Ubiquitous Technologies Limited, Chalandri, Greece
³Department of Electrical and Computer Engineering, University of Western Macedonia, Kozani, Greece
⁴Department of Electrical and Computer Engineering, University of Patras, Patra, Greece
The work reports the developed planning algorithms for optimum resource allocation over a dynamic 5G infrastructure, addressing all involved types of system resources, from the radio access domain to the MEC domain through the Optical Distribution Network (ODN). A modular modelling design is adopted considering these three domains. In that manner, allocation is composed of three optimization phases, which are executed sequentially and ensure optimal end-to-end allocation of resources. The first allocation phase focuses on the over-the-air resources, which are directly assigned to the 5G mobile users. The key entities for radio access are the Remote Radio Heads (RRHs), which are placed at the edge of the network fronthaul and provide wireless communication slots to the User Equipment (UE). Beamforming capabilities are also assumed allowing each RRH to support simultaneous and independent transmission of multiple directed beams to provide high quality targeted coverage. The resource allocation scheme is responsible for assigning subchannels within specific beams to address the bandwidth requirements of the requested services. The translation from the requested data-rate and the allocated bandwidth is based on the characteristics of 3GPP New Radio (NR) standard. Furthermore, the radio resource allocation process is responsible for assigning different bands for optimal frequency reuse within the available spectrum and avoids interference. The formulated ILP optimization problem, which is solvable in close to real-time due to its low computational complexity, allows dynamic adaptation to requests and resources, with a target to minimize energy consumption. The latter is achievable through the aggregation of wireless resources into individual beams and RRHs. In order to further enhance this process, an RRH prioritization algorithm is introduced for weighting the candidate allocations. With the completion of the first allocation phase, the optical resource allocation phase is initiated. The considered architecture follows that of the EU funded blueSPACE project and consists of a fully flexible ODN exploiting the cutting-edge capabilities of Spectrally Spatially Flexible Optical Networks (SS-FONs). In this context, the allocator considers the spectral and/or spatial multiplexing features of the optical nodes for performing elastic switching. The aim is to establish complete optical routes (lightpaths) from the radio access domain to the Central Office (CO). In particular, the output of this allocation phase is utilized to determine end-to-end fiber-based connections between BBUs and beams. The formulated optimization problem (a low complexity ILP) is able to model any type of network topology and provide optimal paths to dynamic demands according to the available optical domain resources. Power saving is achieved by minimizing the number of the optical elements used for building the required lightpaths. The last allocation phase assigns MEC resources within the blueSPACE virtual Content Delivery Network (vCDN) and Evolved Packet Core (vEPC). The services request MEC resources to offload computationally demanding tasks (such as real-time multimedia processing) and the allocator is responsible to make optimal decisions for the hosting of the required VM instances. The formulated ILP problem provides such a fast decision-making mechanism, while averting the scattering of allocated resources to numerous physical servers in order to conserve energy. With the termination of this third phase, all required network and computing resources are fully allocated for serving dedicated enhanced Mobile Broadband (eMBB) slices. The aforementioned resource allocation algorithms are implemented and simulated in MATLAB. For the evaluation process, two real-world simulation scenarios are considered to assess the allocation effectiveness and energy conservation capabilities for changing traffic requests. One scenario simulates a 5G deployment over a football stadium and the second scenario a deployment over a city park. Due to their coverage requirements the two scenarios lead to different RRH location and connectivity properties. Results show that in the “Stadium” scenario we achieve 50% savings in the number of activated RRHs and beams, while in the “City Park” scenario this metric reaches 67%. With respect to the allocation of optical networking resources, our optimization approach achieves conservation of up to 11% of optical ports and 14% of optical cores for the stadium scenario, while the corresponding results for the “City Park” scenario are 9% and 16%, respectively. Lastly, regarding the MEC resource allocation, the conducted simulations in the context of the “Stadium” scenario have shown 22% average reduction of the activated physical MEC servers (reaching up to 38%), while in the “City Park” scenario these savings average even higher to 68% (reaching up to 91%).

Sergei Turitsyn
The design principles of fibre-wireless integration in the incoming mobile communication networks
M. E. Belkin¹, M. Kamalian-Kopae², and S. K. Turitsyn^2
1Scientific and Technological Center “Integrated Microwave Photonics”, MIREA - Russian Technological University, Moscow, Russia
²Aston University, Birmingham, UK
The goal of the talk is to highlight the key tendencies in architecture and technological design principles of Mobile Communication Networks on the way from 4G LTE to 5G NR and 6G. We address broadband fibre-wireless integration techniques beyond 4G including millimetre-wave and sub-terahertz wireless distribution, small-cell scenario and Radio-over-Fiber concept for access network as well as Microwave-Photonics-based approach for the network and user facilities. The above mentioned methods are devised to fulfil the growing demand of wireless access network pushing for wider bandwidth, more power efficiency, and cheaper devices. We, in particular, focus here on the photonic solutions at the final stage of delivering the signal to end users which consists of multiple-beam array antenna and MIMO feeding networks. Photonic-based solutions at this stage have the advantage of small-size and wide bandwidth compared to their RF counterparts. This paves the way for designing remote radio heads with considerably smaller footprint, capable of supporting advanced 5G New Radio features.

Christos Verikoukis
End-to-end delay performance of analog fiber wireless architecture for 5G NR fronthaul
E. Datsika¹, J. Vardakas¹, G. Kalfas², C. Vagionas², A. Mesodiakaki², and C. Verikoukis^3
1Iquadrat Informatica, Barcelona, Spain
²Dept. of Informatics, Aristotle University of Thessaloniki, Greece
³Telecommunications Technological Centre of Catalonia, Castelldefels, Spain
The convergence of fiber and wireless systems based on millimeter-wave (mmWave) bands seems to be a promising fronthaul solution for the fifth generation (5G) centralized radio access network (C-RAN) deployments. The 5G fronthaul allows the flexible splitting of functionalities between centralized and remote units but requires high data rates. These can be achieved by combining the traits of analog radio-over-fiber (RoF) communication, the wide mmWave spectrum and the availability of different functional splits. To that end, we focus on a novel RoF fronthaul architecture and evaluate its performance in terms of end-to-end packet delay under different network setups. Our simulation results show that the experienced delay is affected by the fronthaul load but remains below 100 μs in most cases.

 

Flex-ON invited presentations:

Raul Almeida Jr.
Heuristic routing and spectrum assignment algorithm considering the split spectrum technique
C. J. N Lira, D. A. R. Chaves, and R. C. Almeida Jr.
Federal University of Pernambuco (UFPE), Department of Electronics and Systems, Recife, Brazil
This paper proposes an efficient routing and spectrum assignment strategy for the Split Spectrum technique in Elastic Optical Networks. By strategically choosing appropriate forms of spectrum division and routing selection, it is shown that the network performance can be improved related to that of traditional strategies

Andrea Bianco
Modulation format, core and spectrum assignment in a multicore optical link with and without MIMO receivers
C. Rottondi, G. Bosco, A. Carena, and A. Bianco
Dipartimento di Elettronica, Politecnico di Torino, Italy
We study the modulation format, core and spectrum assignment problem in a multi-core flexi-grid optical link, under the assumption that MIMO receivers can operate on various core subsets and considering distance-adaptive reaches for different modulation formats. Results obtained with optimal and heuristic approaches are discussed, comparing scenarios with and without the use of MIMO transmission.

Vincenzo Eramo
Study and investigation of SARIMA-based traffic prediction models for the resource allocation in NFV networks with elastic optical interconnection
V. Eramo¹, T. Catena¹, F.G. Lavacca², and F. Di Giorgio^1
1DIET, ”Sapienza” University of Rome, Italy
²Fondazione Ugo Bordoni, Roma, Italy
The paper investigates resource allocation problems in Network Function Virtualization (NFV) networks in which the datacenters are interconnected by an Elastic Optical Network and the offered traffic is predicted by a Seasonal Autoregressive Integrated Moving Average (SARIMA) model. We show the procedure for deseasonalizing, eliminating the trend, estimating the parameters of the SARIMA model and forecasting the traffic values. The procedures is applied to real traffic. Its application allows for the evaluation of the total cost increase that the traffic prediction involves in NFV environments with respect to the case in which the traffic is known exactly. In particular the following two cost components are investigated: i) the increase in allocated bandwidth and cloud resource costs occurring when a higher resource provisioning is accomplished due to traffic overestimation; ii) the Quality of Service (QoS) degradation cost due to the user traffic loss occurring when the traffic is underestimated and fewer resources than needed are allocated.

Andrea Fumagalli
A comparative study on variable vs. fixed subchannel symbol rates with different modulation formats in WSS filtering penalty aware elastic optical network
Tianliang Zhang¹, M. Al-Qadi², S. Azadeh¹, Rongqing Hui², and A. Fumagalli^1
1OpNeAR Lab, The University of Texas at Dallas, Richardson, TX, USA
²University of Kansas, Lawrence, KS, USA
The impact of the wavelength selective switch (WSS) filtering penalty in the signal integrity of elastic wavelength division multiplexing (WDM) network becomes increasing important as the optical channel spacing goes finer in order to achieve higher spectrum utilization. Subcarrier multiplexing can be applied to mitigate the WSS filter penalty. We investigate the use of multiple subcarriers with variable symbol rates and different modulation formats to best mitigate transmission penalty caused by WSS filtering. Achievable lightpath signal feasibility using the discussed technique is studied in a relatively small network topology through modelling and simulation.
Keywords: subcarrier multiplexing, WSS penalty, optical signal to noise ratio, elastic optical network.

Xavier Hesselbach
NFV-enabled optimal spectrum allocation in flex-grid optical networks
C. Tipantuña^1,2 and X. Hesselbach^1
1Department of Network Engineering, Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
²Department of Electronics, Telecommunications and Information Networks, Escuela Politécnica Nacional, Quito, Ecuador
This paper proposes an NFV-Enabled optimal spectrum allocation solution applicable to fixed-grid and flex-grid wavelength division multiplexing (WDM) optical networks. By exploiting the frequency shifting capability of individual lightpaths, the proposed approach aims at recalculating the initial spectrum allocation in order to eliminate the unusable gaps between occupied frequency slots. Then, the available spectrum can be used for future connections, which enables the maximization of spectrum utilization. In this regard, this paper describes the NFV-enabled scheme and its operation. Then, the optimization problem is formulated as an Integer Linear Program (ILP). The problem is solved optimally using an exact brute-force search-based wavelength scheduling strategy (OptFs). Given the NP-Hard nature of the optimization problem and the non-polynomial complexity of OptFs, a suboptimal faster heuristic strategy (FastFs), based on a pre-partition method, is proposed. Simulation results validate the performance of the proposed optimal spectrum allocation approach, and the exact and heuristic solutions, compared to the non-application of strategies, demonstrate improvements in spectrum utilization and a better spectral efficiency while offering a dynamic network operation and higher data rates.
Keywords: flexible grid, NFV, optical networks, spectrum allocation, wavelength scheduling, WDM networks.

Ariel Leiva López
3R regeneration in elastic optical networks and its impact on the network quality of service
D. Bórquez-Paredes¹, F. Calderón², N. Jara³, A. Leiva², A. Lozada³, R. Olivares³, and G. Saavedra^4
1Universidad Adolfo Ibáñez, Chile
²Pontificia Universidad Católica de Valparaíso, Chile
³Universidad Técnica Federico Santa María, Chile
⁴Universidad de Concepción, Chile
Signal re-amplification, re-shaping and re-timing (3R) optical regeneration is a key function to scale elastic optical networks. These devices are especially important on large-scale optical networks, enabling long-distance communications. In this work, we analyze the impact of these devices on the blocking probability in wide-area optical networks. To this end, we performed network simulations to obtain the blocking probability of users on diverse scenarios, modifying the number of regeneration devices per node jointly with several parameters such as link distances, bit-error rate (BER) threshold, and network capacity. We use a physical layer model considering linear and non-linear impairments to compute the reach of each communication for a given bit-rate and modulation format for a variety of BER threshold. The results showed the importance of using regeneration devices in wide-area elastic optical networks (EON). Notwithstanding, there is a limit on adding regenerators per node since more will not substantially improve the blocking probability, considering the extra cost involved in installing more of these devices.

Eiji Oki
Performance of hitless defragmentation with rerouting for quasi 1+1 protected elastic optical networks
E. Oki¹, T. Sawa¹, F. He¹, T. Sato¹, and B. C. Chatterjee^2
1Kyoto University, Kyoto, Japan
²South Asian University, New Delhi, India
This paper analyses the performance of the defragmentation scheme using path exchanging in 1+1 path protected elastic optical networks (EONs), which is intended to improve the traffic admissibility in the network. The defragmentation scheme reallocates spectrum slots of backup paths and allows to reroute the backup paths. The path exchange function of the defragmentation scheme makes the primary paths become the backup state while the backup paths become the primary. The simulation results show that the defragmentation scheme with path exchanging and rerouting outperforms the conventional schemes in terms of resource utilization and traffic admissibility. This paper analyses the performance of the defragmentation scheme using path exchanging in 1+1 path protected elastic optical networks (EONs), which is intended to improve the traffic admissibility in the network. The defragmentation scheme reallocates spectrum slots of backup paths and allows to reroute the backup paths. The path exchange function of the defragmentation scheme makes the primary paths become the backup state while the backup paths become the primary. The simulation results show that the defragmentation scheme with path exchanging and rerouting outperforms the conventional schemes in terms of resource utilization and traffic admissibility.

 

GOC invited presentations:

Michał Aibin
Energy consumption reduction of the survivable spectrally-spatially flexible optical networks
M. Aibin, J. Gotengco, J. Tran, J. Soukchamroeun, C. Vinchoff, and N. Chung
British Columbia Institute of Technology, Vancouver, Canada
Energy reduction is rapidly gaining interest due to several environmental changes in our society. In this paper, we design an energy-efficient algorithm for the problem of Routing, Modulation, Core and Spectrum Assignment in Spectrally-Spatially Flexible Optical Networks (SS-FON) with the network survivability. We then evaluate it using existing, real-life networks in the CEONS simulator. Two primary metrics of the evaluation are operational expenditure (OPEX) and Bandwidth Blocking Probability (BBP). The numerical experiments confirm the efficiency of our solution compared to the ones existing in the literature.
Keywords: optical networks, optimization, energy, SDM, EON, FON, routing.

Patricia Layec
Transforming digital-to-analog interfaces for cost sensitive optical transport
S. Almonacil, F. Boitier, and P. Layec
Nokia, Paris, France
Digital/Analog Converters represent a significant part of the power consumption and the cost of recent optical transmitters and receivers, especially when they come with a high, but typical, resolution of 8 bits or more. The purpose of the paper would be to review performance models and experiments of low-resolution converters (typ. 5 bits or below) and show that they are very promising alternatives, as long as they are carefully designed, and possibly enhanced to narrow the performance gap with high resolution converters.

Silvia Pato
High-performance versus power-efficient coherent optical interfaces: Spectral efficiency and hardware count comparison
J. Pedro^1,2 and S. Pato^3
1Infinera Unipessoal Lda, Carnaxide, Portugal
²Instituto de Telecomunicações, Instituto Superior TécnicoLisboa, Portugal
³Instituto de Telecomunicações, DEEC, Universidade de Coimbra, Portugal
Power-efficient coherent optical interfaces are being developed to meet the increasingly demanding capacity and footprint requirements of data center interconnection (DCI) applications. Simultaneously, progress is being made in high-performance interfaces, traditionally addressing high-end applications, which is the case of long-haul and subsea deployments. Interestingly, both types of coherent interfaces may compete directly in the metro and regional network segments. This paper provides insight on how both types of interfaces are expected to perform in these networks. With that aim, a set of media channel (MCh) formats to be supported with each type of optical interfaces is introduced along with suitable MCh provisioning algorithms that mimic network operation over multiple periods. The simulation results obtained in reference networks highlight the extent of hardware savings and additional carried traffic load when coherent interfaces designed primarily for high-performance are used instead of alternative implementations that relax performance requirements.

 

GOWN invited presentations:

Abhishek Dixit
Radio over fiber based fronthaul for next-generation 5G networks
G. Pandey, A. Choudhary, and A. Dixit
Department of Electrical Engineering, IIT Delhi, New Delhi, India
In this paper, we propose and experimentally demonstrate frequency and wavelength-division multiplexed (FWDM)-radio-over-fiber (RoF) network for application in the fronthaul of next-generation 5G mobile networks by using a cost-efficient directly modulated laser (DML). Furthermore, we use spectrally efficient M-ary quadrature-amplitude modulation (M-QAM) in the proposed FWDM-RoF network. For the experiment, we consider three frequency channels with a symbol rate of 250 MBd (megabaud) on two optical wavelengths and multiplexed in the wavelength domain for transmission over the network. The error vector magnitudes (EVM) of the overall link for 4/16/64-QAM are below the 3GPP standard for 5G. From the results of the experimental setup, it is evident that 4-QAM, 16-QAM, and 64-QAM transmit up to an optical link length of 55 km, 40 km, and 30 km, respectively, for a symbol rate of 250 MBd for all three radio frequencies and two optical wavelengths. The results of the proposed FWDM-RoF network using DML indicate that it is a cost-efficient deployment solution for application as the fronthaul network in 5G mobile networks.
Keywords: Radio-over-fiber (RoF), directly modulated laser (DML), spectral efficiency, M-QAM, wavelength division multiplexing (WDM).

Vincenzo Petruzzelli
Assessment of on-chip wireless communication networks based on integrated dielectric antennas
G. Calò¹, G. Bellanca², F. Fuschini³, M. Barbiroli³, V. Tralli², M. Bozzetti¹, B. Alam¹, T. Stomeo⁴, J. Nanni², J. Shafiei Dehkordi², and V. Petruzzelli^1
1Department of Electrical and Information Engineering, Politecnico di Bari, Bari, Italy
²Department of Engineering, University of Ferrara, Ferrara, Italy
³Department of Electrical, Electronic and Information Engineering, University of Bologna, Bologna, Italy
⁴Istituto Italiano di Tecnologia, Center for Biomolecular Nanotechnologies, Arnesano, Italy
Optical wireless network-on-chip systems are novel solutions able to promote the development of kilo-cores architectures characterized by high computation capacity. Moreover, they assure simplified network layout and reduced communication latency, easing the antenna on-chip integration process. On the other hand, interference issues and propagation losses could represent strong limits on the communication performance. This paper reports the details of the methodology to evaluate the assessment of optical wireless networks-on-chip by integrating dielectric antennas. In particular, a multi-level approach is used by spanning from the optical antenna design and wireless channel modeling to management and mitigation of interference issues, with special attention to the impact of noise and interference on bit-error-probability and maximum achievable communication link distances.

 

LFSRS invited presentations:

Marina Cunquero Navarro
Calcium imaging in ex vivo rat retinas for new generation retinal prostheses
M. Cunquero¹, M. Marsal¹, S. T. Walston², J.-G. Macías-Montero³, M. Chmeissani³, J. A. Garrido^2,4, D. Merino^1,5, and P. Loza-Álvarez^1
1ICFO, Institute of Photonic Sciences, Castelldefels (Barcelona), BIST-Barcelona Institute of Science and Technology, Spain
²ICN2, Catalan Institute of Nanoscience and Nanotechnology, CSIC and The Barcelona Institute of Science and Technology, Spain
³IFAE, The Institute for High Energy Physics, Universitat Autònoma de Barcelona, BIST-Barcelona Institute of Science and Technology, Spain
⁴ICREA, Barcelona, Spain
⁵UOC, Universitat Oberta de Catalunya (Barcelona), Spain
Some retinopathies result in the loss and malfunction of photoreceptors. Retinal prostheses can partially restore sight in blind patients by electrically stimulating the retinal ganglion cells (RGC) through a microelectrode array (MEA) implanted on the retina. Current commercial technologies offer low spatial resolution and poor focal activation of RGCs due, in part, to the low number of electrodes. With the aim of improving current technologies, a multidisciplinary team has enabled an in vitro calcium imaging study in which the neural activity of RGCs in rat retinas is observed in response to electrical stimulation by graphene microelectrodes. Calcium imaging allows for real-time spatial mapping of RGC activity and provides insights into the vision quality that can be restored to patients. We demonstrate that electrical stimulation successfully activates RGCs in correlation with the delivered stimulus pattern. In efforts to achieve focal activation, several stimulation schemes have been evaluated and they elucidate different patterns of activity. KEYWORDS: calcium imaging, retinal prostheses, electrical stimulation.

Mikko Huttunen
Fast tissue investigation using label-free point- and angle-scanning widefield multiphoton microscopies
M. J. Huttunen and A. Kiviniemi
Photonics Laboratory, Physics Unit, Tampere University, Finland
Multiphoton microscopy has recently emerged as a powerful high-resolution and label-free imaging modality to study biological specimens in-vivo. Multiphoton modalities require minimal sample preparation showing potential in applications benefitting from fast imaging protocols, such as in medical diagnosis. Here, we overview our recent work on this topic focusing on technique development that could provide fast imaging capabilities to rival conventional imaging modalities. In particular, we demonstrate a novel widefield multiphoton technique that greatly facilitates wavelength-scanning multimodal imaging.
Keywords: nonlinear imaging, multiphoton, two-photon excitation fluorescence, second-harmonic generation.

Konstantinos Iliopoulos
Using chalcogenide thin films for super-resolution nano fabrication
R.-N. Verrone, C. Moisset, J. Lumeau, and J. Y. Natoli
Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France
In this work we deposit thin Sb₂Te₃ films by means of the electron beam deposition technique. An annealing of the thin films is performed in order to obtain well defined crystalline structure and enhanced optical nonlinearities. The optical nonlinearities are determined by the Z-scan technique and the results are compared with previous findings in the literature. The possibility to use these masks for reducing the size of a laser beam is discussed. The target of this work is surpassing the diffraction limit in order to perform super resolved nanostructuring.

Sviatlana Kalinina
Luminescence lifetime imaging for cell metabolism and oxygen sensing
S. Kalinina¹, I. S. Kritchenkov², S. P. Tunik², and A. Rueck^1
1Core Facility Confocal and Multiphoton Microscopy, University of Ulm, Germany
²Institute of Chemistry, St. Petersburg State University, Russia
Non-invasive and information-rich optical imaging technologies based on time correlated single photon counting (TCSPC) have found a wide application in medicine and biology. In combination with multiphoton laser scanning microscopy, TCSPC systems are successfully used in fluorescence lifetime imaging microscopy (FLIM), for example, for imaging of intrinsic metabolic coenzymes as NAD(P)H and FAD+ in living cells and tissues. Since the coenzymes exist in protein-bound and free forms distinguished by different fluorescence lifetimes, the measurements provided by FLIM give an information about cellular metabolic status. The changes in fluorescence lifetime are relevant for many disorders on the cellular level including neurodegenerative diseases and cancers. Our multichannel detection system was designed for monitoring the metabolic status of the living cells by FLIM. The unique upgrade of the construction enables to perform FLIM and PLIM (phosphorescence lifetime imaging microscopy) simultaneously. Phosphorescence lifetime measurements enables oxygen sensing in biomedical samples due to an oxygen-dependent quenching of phosphorescence of some compounds on the base of transition metals such as ruthenium(II) and iridium(III). With the two-channel FLIM/PLIM system we monitor intrinsic oxygen partial pressure (pO₂) by PLIM simultaneously with NAD(P)H by FLIM providing complex metabolic and pO₂ imaging of living cells.
Keywords: multiphoton microscopy, FLIM, PLIM, cell metabolism, oxygen sensing, transition metals.

Martin Leahy
Stem cell tracking in vivo
M. J. Leahy, National University of Ireland, Galway
Stem cells have shown great promise in the treatment of many diseases. However, clinical translation requires regulatory approval in most cases which in turn requires good data on the biodistribution and impact in vivo. However, tracking small numbers of cells in vivo is a challenging task. This paper will discuss the options and the methods we have developed to track stem cells in vivo in large animals and humans.

Sylvain Lecler
Phase compensation in diffraction-limited microsphere-assisted 3D microscopy
S. Lecler^1,2, S. Perrin¹, R. Boudoukha^1,3, A. Guessoum³, N.E. Demagh³, and P. Montgomery^1
1ICube Institute, Université de Strasbourg, CNRS, Strasbourg, France
²INSA de Strasbourg, Strasbourg, France
³University of Ferhat Abbas Sétif, Algeria
Adding a dielectric microsphere on a sample in front of a classical microscope objective has been discovered to be a simple way of achieving full-field, label-free, and super-resolution imaging. Breaking the diffraction limit is most probably due to the collection and preservation of near-field details. Our team has been one of the first to have highlighted that this 2D imaging technique can be used in an interferometric configuration in order to increase the spatial resolution in 3D profile reconstruction. The diffraction limit is more difficult to reach in optical profilometry than in classical 2D imaging. We show how the resolution can be improved using glass microspheres. In such an interferometric configuration, the phase response of the sphere must however be removed. Up to now this operation has been performed numerically on the basis of a sphere response estimation. We have experimentally shown how the phase contribution can be physically removed by also adding a similar sphere in the reference arm of the interference setup. The method is not only faster to implement but also clearly allows a higher spatial resolution to be attained.

Hanyang Li
Real-time and sensitive detection of hydrogen peroxide using whispering gallery mode lasing
Rui Duan^1,2, Xiaolei Hao¹, Yichen He¹, and Hanyang Li^1,2
1College of Physics and Optoelectronic Engineering, Harbin Engineering University, China
²Key Lab of In-fiber Integrated Optics, Ministry Education of China, Harbin Engineering University, China
In this study, a real-time and sensitive liquid crystal (LC) biosensor has been developed for detection of hydrogen peroxide concentrations using whispering gallery mode lasing. The biochemically functionalized nematic LC 4-cyano-4’-pentylbiphenyl (5CB) microfiber is fabricated by a simple method and used as an optical microcavity. Lasing emission is observed from micron-sized 5CB microfiber and ascribed to WGMs. The operation principle of our sensors is based on a spectral shift of the WGM peaks and a sub-micromole detection limit of hydrogen peroxide is achieved. We believe that the proposed sensor has potential application value in real-time identification and detection of hydrogen peroxide-related chemical and biological events.

Íñigo Molina-Fernández
Silicon photonic label free biosensors with coherent readout
J. Leuermann^1,2, A. Fernández-Gavela³, R. Halir^1,2, A. Ortega-Moñux^1,2, J. G. Wangüemert-Pérez^1,2, L. M. Lechuga⁴, and I. Molina-Fernández^1,2
1E.T.S.I. Telecomunicación, Universidad de Málaga, Spain
²Bionand Center for Nanomedicine and Biotechnology, Málaga, Spain
³Departamento de Física, Universidad de Oviedo, Spain
⁴Nanobiosensors and Bioanalytical Applications Group, Catalan Institute of Nanoscience and Nanotechnology (ICN2), Barcelona, Spain
Silicon photonics enables sensitive and label-free optical biosensors for the detection of chemical and biological substances. Different sensing architectures have been used to improve the limit of detection and increase dynamic range of the sensors. In this invited paper we will show state-of-the-art limit of detection experimental results that have been obtained with a Silicon Nitride integrated Mach-Zehnder interferometers with coherent readout. Besides, we will present theoretical results, accompanied with preliminary experimental evidence, that show that the proposed approach enables the use of simple read-out equipment based on low-cost laser sources.
Keywords: label-free biosensors, integrated optics, silicon photonics.

Régis Orobtchouk
Slot ARROW waveguide: A new platform for optical sensing
R. Orobtchouk, P. Rojo-Romeo, and A. Belarouci
Institut des Nanotechnologies de Lyon (INL), CNRS UMR5270, INSA de Lyon, Villeurbanne, France
The realization of high sensitivity integrated photonic sensors requires strong light/matter interaction. Unfortunately, in an optical waveguide, only the evanescent part of the mode interacts with the cladding medium under test. In this context, we have patented a new concept of waveguide [1] called “Slot ARROW”, where the major part of the light is confined in the cladding such as metallic plasmonic and dielectric slot waveguides. This paper presents the modelling, the fabrication and the optical characterization of slot ARROW waveguides. Optical modelling shows that the main advantages of Slot ARROW waveguides are a reduction of propagation losses and the sustaining monomode condition for widths 100 times larger than the slot or plasmonic waveguides. The fabrication process is more robust as it only needs the structuration of the upper layer with standard optical lithography and a RIE etching step. The critical lateral dimension is relaxed to 0.9 µm compared to 0.1 µm for the grooves of slot or plasmonic 2D waveguides. Basic building blocks for optical routing have been designed and preliminary characterizations demonstrate the validity of this new concept.
[1] R. Orobtchouk, "Nouveau guide d’optique intégrée utilisant une combinaison d’effets SLOT ARROW", patent FR1555755, 23.06.2015.

Luiz Poffo
Optical sensors using ultrahigh-quality micro-resonators
L. Poffo¹, L. Ruel¹, C. Pareige¹, Y. Dumeige¹, M. Mortier², and P. Feron^1
1Université de Rennes, CNRS, Institut FOTON – UMR 6082, Lannion, France
²PSL Research University, Chimie ParisTech – CNRS, Institut de Recherche de Chimie de Paris, France
Whispering gallery mode microresonators have been used in various sensing applications. They are normally made of melted glass and can have a quality (Q) factor around 10⁸. We propose to provide optical gain to the microresonator by using erbium ions to increase Q-factor up to 10⁹. By controlling pumping and coupling regime we can allow the transmission and dispersive properties of perfectly transparent microresonator. For sensor applications, this control would be proportional to the concentration of the element being measured, ensuring high sensitivity.

Junsuk Rho
Recent progress in metamaterials-based imaging
Junsuk Rho, Departments of Mechanical and Chemical Engineering, Pohang University of Science and Technology (POSTECH), Republic of Korea
Here, recent efforts on metamaterials-based super-resolution imaging techniques including hyperlens and metasurfaces-integrated systems for practical devices will be discussed. First, we demonstrate a super-resolution imaging device called hyperlens. Hyperlens is a metamaterial-based imaging device whose super-resolving power comes from the hyperbolic dispersion relation in anisotropic media, which enables the sub-diffraction-limited objects to be resolved in the far-field. We demonstrate the 4-inch wafer-scale array of hyperlenses using nanoimprint lithography and it can be integrated into a conventional microscopy system for imaging biomolecular objects with resolution down to 151 nm. We also propose a flat hyperlens, which can be achieved by coordinate transformation from a curved hyperlens. It can be a replacement for conventional hyperlens by solving the difficulties of placing a sample on the curved surface. We will further discuss our recent effort to integrate such hyperlens into the conventional light microscope which can realize a truly real-time nanoscope along with a compact attachable super-resolution module. Second, we propose metasurfaces applications that enable enhancement of resolution of the fluorescence microscopy. Two different dielectric metasurfaces are designed to control confinement of the excitation point spread function and to provide encoded illumination patterns for patterned illumination. The results show the axial- and lateral-resolution improvement, respectively, and demonstrate applicability and practical use to conventional optical systems. These unique techniques mentioned in this talk will provide an opportunity to achieve practical metamaterial devices as an important step in nanoscience to nanotechnology.
[1] Rho, J., Ye, Z., Xiong, Y., Yin, X., Liu, Z., Choi, H., Bartal, G., Zhang, X. "Spherical hyperlens for two-dimensional sub-diffractional imaging at visible frequencies", Nat. Commun. 1, 143 (2010).
[2] Rho, J. "Far-field imaging: new dimension for hyperlens", Nat. Photonics 5, 128-129 (2011).
[3] Yang, X., Yao, J., Rho, J., Yin, X., Zhang, X. "Experimental realization of three-dimensional indefinite cavities at the nanoscale with anomalous scaling laws", Nat. Photonics 6, 450-454 (2012).
[4] Kim, M., Rho, J. "Metamaterials and imaging", Nano Convergence 2, 22 (2015).
[5] Kim, M., Lee, D., Rho, J. "High-throughput super-resolution hyperlens imaging", SPIE Newsroom (2016).
[6] Kim, M., So, S., Yao, K., Liu, Y., Rho, J. "Deep sub-wavelength nanofocusing of UV-visible light by hyperbolic metamaterials", Sci. Rep. 6, 38645 (2016).
[7] Byun, M., Lee, D., Kim, M., Kim, Y. D., Kim, K., Ok, J. G., Rho, J. "Demonstration of nanoimprinted hyperlens array for high-throughput sub-diffraction imaging", Sci. Rep. 7, 46314 (2017).
[8] Lee, D., Kim, M., So, S., Kim, I., Yoon, G., Kim, K., Rho, J. "Demonstration of a hyperlens-integrated microscope and super-resolution imaging", J. Vis. Exp. 127, e55968 (2017).
[9] Lee, D., Kim, Y. D., Kim, M., So, S., Choi, H.-J., Mun, J., Nguyen, D. M., Badloe, T., Ok, J. G., Kim, K., Lee, H., Rho, J. "Realization of wafer-scale hyperlens device for sub-diffractional biomolecular imaging", ACS Photonics 5, 2549-2554 (2018).
[10] So, S., Kim, M., Lee, D., Nguyen, D. M., Rho, J. "Overcoming diffraction limit: from microscopy to nanoscopy", Appl. Spectrosc. Rev. 53, 290-812 (2018).
[11] So, S., Rho, J. "Geometrically flat hyperlens designed by transformation optics", J. Phys. D 52, 194003 (2019).
[12] Lee, D., Yang, Y., Yoon, G., Kim, M., Rho, J. “Resolution enhancement of fluorescence microscopy using encoded patterns from all-dielectric metasurfaces”, Appl. Phys. Lett. 115, 101102 (2019).
[13] Lee, D., Kim, M., Kim, J., Hong, H., Kim, D. S., Rho, J. “All-dielectric metasurface to enhance axial resolution in laser scanning microscopy”, Opt. Mater. Express 9, 3248-3259 (2019).

Constantin Simovski
How a simple microsphere offers a non-resonant subwavelength resolution
C. R. Simovski and R. Heydarian
Aalto University, Helsinki, Finland
Recently it was experimentally revealed that a simple glass microsphere grants the same functionality that the famous metamaterial hyperlens – label-free subwavelength resolution in the far field with a large magnification. Moreover, its resolution is much finer than that can be granted by any feasible hyperlens and the achieved magnification is higher incomparably. Therefore, a tapered nanostructure fabricated with an Angstrom precision is replaced by a simple glass (or highly refractive transparent dielectric, that grants even better operation) with a simultaneous gain in the nanoimaging. It is amazing, but a so exciting result has not been reasonably explained. Different attempts to explain it either referred to narrow-band resonant mechanisms, whereas the observed nanoimaging was broadband, or wrongly related the nanoimaging to the so-called photonic nanojet arising in a microsphere impinged by a plane wave. This phenomenon has nothing to do with this nanoimaging. We assumed that a microsphere on a dielectric substrate grants several non-resonant mechanisms of nanoimaging. For two of them the substrate is not relevant. Both these mechanisms solely related to the curvature of the microlens imply that the pointwise scatterers to be spatially resolved are polarized normally with respect to the sphere. The first mechanism is a geometric optical diffraction-free resolution. It arises due to formation of a low-divergence and low-diffraction imaging beam by one scatterer. In this case, the subwavelength resolution in the non-coherent light is possible and the magnification of a complex object should be huge. The second assumed mechanism is formation of a Bessel-like or a Mathieu-like imaging beam representing a set of partial beams which are also diffraction-free. In his case, only a coherent imaging is possible that demands the non-symmetric excitation of the object by laser light. Both these assumptions were confirmed by exact numerical simulations in the 2D geometry.

 

MALOC invited presentations:

Abdelkerim Amari
Probabilistic shaping for PAM-8 optical Ethernet systems
A. Amari and A. Richter
VPIphotonics, Berlin, Germany
A performance comparison of probabilistically shaped (PS) pulse amplitude modulation (PAM)-8 and uniform PAM-8 is performed in the context of 168 Gb/s intensity modulation and direct detect (IMDD) optical Ethernet system. PS-PAM-8 provides gain in terms of the optical signal-to-noise ratio of about 1.2 dB in the back-to-back system, and an increase of more than 10% in transmission reach at the 20% low-density parity-check (LDPC) soft decision forward error correction (FEC) threshold.
Keywords: optical Ethernet, probabilistic shaping, pulse amplitude modulation.

Clara Catanese
An overview on machine learning-based solutions to improve lightpath QoT estimation
R. Ayassi^1,2, A. Triki¹, M. Laye¹, N. Crespi², R. Minerva², and C. Catanese^1
1Orange Labs, Lannion, France
²Institut Polytechnique de Paris, Institut Mines-Telecom, Telecom SudParis, France
Estimating lightpath Quality of Transmission (QoT) is crucial in network design and service provisioning. Recent studies have turned to Machine Learning (ML) techniques to improve the accuracy of QoT estimation. We distinguish two categories of solutions: the first category aims to build ML-based QoT estimation models that outperform the analytical model while the second category uses ML algorithms to reduce uncertainties on parameters provided as input to analytical model. In this overview, we describe the solutions in each category and discuss their practical feasibility and added benefit for operational networks.
Keywords: machine learning, WDM networks, QoT.

Enrico Ghillino
Machine learning assisted abstraction of photonic integrated circuits in fully disaggregated transparent optical networks
I. Khan¹, M. Chalony², E. Ghillino³, M. Umar Masood¹, J. Patel³, D. Richards⁴, P. Mena³, P. Bardella¹, A. Carena¹, and V. Curri^1
1DET, Politecnico di Torino, Italy
²Light Tec SARL, Italy
³Photonic Solutions, Synopsys, Italy
⁴The College of Staten Island, CUNY, USA
Optical networks are fast evolving towards full disaggregation and softwarization down to layer-0: the data transport layer. Moreover, network elements are progressively exploiting photonic integrated circuits (PICs) to perform complex functions at the photonic level. Thanks to advanced simulation tools, also the behavior of photonic integrated circuits can be abstracted and used within the SDN paradigm for network planning and management, permitting a full network disaggregation and softwarization down to below layer-0. To this aim, one of the main issues is the need for exact knowledge of the physical parameters of integrated circuits. In this work, we use machine learning techniques to deliver an augmented knowledge of the physical parameters of integrated circuits to be used for their full and accurate softwarization. We consider both the inverse design and the performance prediction problems. Overall results as well as data sets for machine-learning training are obtained by leveraging the integrated software environment of the Synopsys Photonic Design Suite.

Helmut Griesser
Machine learning based data driven diagnostic and prognostic approach for laser reliability enhancement
K. Abdelli^1,2, H. Griesser¹, and S. Pachnicke^2
1ADVA Optical Networking SE, Munich/Martinsried, Germany
² Christian-Albrechts-Universität zu Kiel, Germany
In this paper, a data-driven diagnostic and prognostic approach based on machine learning is proposed to detect laser failure modes and to predict the remaining useful life (RUL) of a laser during its operation. We present an architecture of the proposed cognitive predictive maintenance framework and demonstrate its effectiveness using synthetic data.
Keywords: laser reliability, machine learning, prognostics, diagnostics.

Lorenzo Pavesi
Neuromorphic photonics for mitigation of optical nonlinearities in fiber optics communications
L. Pavesi, Department of Physics, University of Trento, Italy
Recently, there have been a renewed interest on brain-inspired (neuromorphic) computing schemes that are directly implemented on a physical platform. In fact, such optical or electrical platforms allow performing important computational tasks at a speed much higher than the software-based counterparts. Unlike the Von Neumann architecture, brain-inspired architectures delocalize the core computing and the memory along the network allowing to achieve fast and low-power consumption data processing. A potential rewarding application of neuromorphic computing is in optical fibre communication. Indeed, nowadays the data rate per channel in a fibre link easily exceed 100 Gb/s. This imposes to use, at the receiver side, a real time data processor to compensate for possible data distortion. This is usually performed in the electric domain by costly and power-hungry Digital Signal Processors. Here we propose to use neuromorphic silicon photonics to recover data integrity directly in the optical domain outperforming the electronic performances.

Aleksejs Udalcovs
A machine-learning-aided scheme for proactive interference monitoring in optical networks using spectrum diagrams only
A. Udalcovs¹, Yuchuan Fan^2,1, S. Gutiérrez², R. Mochaourab¹, S. Sinha¹, C. Natalino³, M. Furdek³, A. Djupsjöbacka¹, J. Mårtensson¹, S. Popov², and O. Ozolins^1,2
1Networks Unit, RISE Research Institute of Sweden AB, Kista, Sweden
²School of Engineering Sciences, KTH Royal Institute of Technology, Stockholm, Sweden
³Department of Electrical Engineering, Chalmers University of Technology, Gothenburg, Sweden
Undoubtedly, machine learning (ML)-based algorithms are considered as critical enablers of autonomous network reconfiguration based on telemetry data received from disaggregated nodes and other monitoring equipment deployed in a network [1]. ML finds its niche in applications such as (i) quality of transmission (QoT) prediction [2], (ii) bitrate and modulation format identification (B&MFI) [3],[4], (iii) signal parameter adjustment [5], (iv) resource allocation and optimization [6], and (v) anomaly and physical layer (PHY) attack detection [7][8]. The latter has elevated interest due to its ability to spot anomalies even without specific knowledge about their signatures, which enables trigger alarms, classifying incidents and counteracting an attack without necessarily involving a human operator [8]. However, optical telemetry data must be pre-processed, which sometimes involves a data pre-selection, some-sort of furnishing, for a specific ML objective, which imposes additional complexity and uncertainty in terms of the most suitable methods and approaches. Thereby, an interoperable input for a wide range of models assessing the performance of optical networks are being explored. Both signal spectrum diagrams and constellation diagrams are showing a potential to become such universal input [4][9] since they both can be easily interpreted by a human operator and as an input to a ML algorithms. Moreover, they are characterizing the received signal and contain a unique fingerprint of the optical channel. In this work, we focus on spectrum interference detection and classification that relies only on optical spectrum analyzer (OSA)-captured spectrums aiming to explore how interferer power, frequency separation from interfered channel, OSA resolution, signal quality and transmission impairments affect accuracy of the implemented ML scheme. The experimental setup is built in the Kista High Speed Transmission Lab [10] at RISE premises in Stockholm for signal quality measurements and OSA spectrum collection. It consists of two wavelength division multiplexed (WDM) channels (interfered channel: 32 Gbaud 16-level quadrature amplitude modulation (QAM) and interfering channel: 10G on-off keying (OOK)) which are transmitted over ~200 km long fiber-optic link (4×50 km standard single-mode fiber (SMF having ~0.2 dB/km and 16-18 ps/nm/km) spans) with optical dispersion compensation modules (DCM). The accumulated dataset is used for QoT performance characterization and further for ML-schemes training and validation. During the analyses, we do not only assess the accuracy of interference detection schemes but also test and discuss importance of retraining of the developed ML-models when they are applied to other system configurations (link, power, wavelength). This work was supported by VINNOVA – Sweden’s innovation agency, within Centre for Software-Defined Optical Networks (2017-01559) and ASIMOV (2019-03330) projects, and by the Swedish Research Council within the PHASE (2016-04510) project.
Keywords: interference detection and classification, spectrum diagrams, supervised and unsupervised learning, network telemetry, fiber-optic communication.
[1] D. Rafique et al.: Machine learning for network automation: overview, architecture, and applications [invited tutorial], IEEE/OSA Journal of Optical Communications and Networking, vol. 10, no.10, pp. D126 - D143, 2018.
[2] C. Rottondi et al.: Machine-learning method for quality of transmission prediction of unestablished lightpaths, IEEE/OSA Journal of Optical Communications and Networking, vol. 10 , no. 2 , pp. A286 - A297, 2018.
[3] F. N. Khan et al.: Modulation format identification in coherent receivers using deep machine learning, IEEE Photonics Technology Letters, vol. 28, no. 17, pp. 1886–1889, 2016.
[4] C. Natalino et al.: One-shot learning for modulation format identification in evolving optical networks, in OSA Novel Optical Materials and Applications, 29 Jul. 2019, San Francisco, USA, PDP JW4A.2.
[5] S. Savian et al.: Joint estimation of IQ phase and gain imbalances using convolutional neural networks on eye diagrams, in CLEO 2018, San Jose, CA, USA, paper STh1C.3.
[6] M. Bouda et al.: Demonstration of continuous improvement in open optical network design by QoT prediction using machine learning, in OFC 2019, CA, USA, 3-7 Mar. 2019, M3Z.2.
[7] X. Chen et al.: Self-taught anomaly detection with hybrid unsupervised/supervised machine learning in optical networks, IEEE/OSA Journal of Lightwave Technology, vol. 37, no. 7, pp. 1742–1749, 2019.
[8] C. Natalino et al.: Field demonstration of machine-learning-aided detection and identification of jamming attacks in optical networks, in ECOC 2018, Rome, Italy, 23-27 Sep. 2018, pp. 1-3.
[9] A. P. Vela et al.: Soft failure localization during commissioning testing and lightpath operation, IEEE/OSA Journal of Optical Communications and Networking, vol. 10, no. 1., pp. A27 - A36, 2018.
[10] Kista High-Speed Transmission Laboratory (KHST Lab).

Darko Zibar
Machine learning based inverse system learning
T. M. Sá Pinto¹, U. C. De Moura¹, A. Napoli², F. Da Ros¹, and D. Zibar^1
1DTU Fotonik, Technical University of Denmark, Lyngby, Denmark
²Infinera, Munich, Germany
In this paper, it is reviewed now techniques from machine learning such as multi-layer neural networks can be used to perform inverse system learning (ISD). This has great importance for design of Raman amplifiers, optimization of photonic integrated circuits and system optimization.

 

MARS invited presentations:

Germán Arévalo
Optimal deployment of next-generation PON for high and ultra-high bandwidth demand scenarios in large urban areas
D. Ulloa¹, G. V. Arévalo², and R. Gaudino^3
1Pontificia Universidad Católica del Ecuador, Facultad de Ingeniería, Quito, Ecuador
²Universidad Politécnica Salesiana, Quito, Ecuador
³Politecnico di Torino, Italy
This paper proposes a techno-economic analysis of the optimal deployment of multiple PON networks with different technologies, including the newest next-generation standards, such as GPON, XGSPON, NG-PON2 and 50G-EPON, within a large urban area in Quito. On this zone, we simulated a population of around 20000 customers, distributed between two central offices. We assume that customers demand different bitrates considering present and future bitrate-demand scenarios. This analysis uses an algorithm called OTS (Optimal Topology Search) which employs a nested set of heuristics in order to find the optimal topology for the deployment of PON in large areas with many potential customers. Results obtained in this research describe an accurate projection of the optimal deployment cost and the most suitable PON technology for each bitrate demand scenario, taking into account not only the cost of the entire hardware, but leasing, labor-hours, pole-works and trenching/recapping-works.
Keywords: optimal topology search, optical distribution network, passive optical network, GPON, XGSPON, NG-PON2, 50G-EPON.

Marco Forzati
Infrastructure choice to reach Sweden's broadband target: a techno-economic study
M. Forzati and Jie Li
Networking and Transmission Laboratory, RISE Acreo, Kista, Sweden
This study performs an analysis on the cost, energy consumption and performance (in the term of download speed) of optical fibre versus 5G fixed wireless access (FWA) based solutions in order to achieve one of the government’s 2025 broadband goals that 98% of Swedish households and workplaces should have at least 1 Gbit/s broadband access. Alongside with the pure fibre based solution, 3 FWA-based scenarios using existing commercial macro cells, newly installed mmWave small cells, and hybrid macro and small cells.

Massimo Tornatore
A techno-economic comparison of filterless and wavelength-switched optical metro networks
O. Karandin, O. Ayoub, F. Musumeci, and M. Tornatore
Politecnico di Milano, Italy
We estimate the cost of Filterless Optical Networks (FONs) and compare FONs with state-of-the-art Wavelength-Switched Optical Networks (WSON) in a metro area. We show that, due to the energy-efficiency and relatively longer mean-time-between-failures of passive devices, FONs achieve significant cost savings with respect to WSON.

 

MOF invited presentations:

Richard Carter
Flexible high peak power beam delivery: Practical considerations
R. Carter, Heriot-Watt University, Edinburgh, UK
We present work carried out in collaboration between Heriot-Watt and Bath Universities developing hollow core anti-resonant fibres for flexible high peak power beam delivery at the industrially relevant 1 µm wavelength. Practical considerations such as effect of bend losses, coupling tolerance, polarisation, damage threshold, and non-linear limitations of the fibres have all been investigated and demonstrated in an industrial environment.

Francesco De Lucia
Enhanced second-harmonic generation in periodically poled fibers functionalized with intrinsically nonlinear materials
F. De Lucia¹, N. Englebert², A. H. Lewis¹, R. H. S. Bannerman¹, M. M. A. Nunez Velazquez¹, Chung-C. Huang¹, J. C. Gates¹, S.-P. Gorza², J. Sahu¹, F. Leo², D. Hewak¹, and P. J. A. Sazio^1
1Optoelectronics Research Centre, University of Southampton, UK
²OPERA-Photonics, Université libre de Bruxelles, Belgium
We present the most recent results of our research activity on thermal poling of silica fibers. The motivation for our work consists in the outcome of the fabrication of an all-fiber photonic device based on second order nonlinearity. A huge effort has been invested over the last years in the attempt of exploring any potential improvement of the thermal poling technique, ultimately limited by intrinsic technological constraints such as the dielectric strength of silica and its χ⁽³⁾. In this paper we report the early steps towards a new approach to the full exploitation of thermal poling technique, based on the combined effect of the effective second order nonlinearity created via thermal poling and the intrinsic nonlinear properties of some semiconductor materials (2D metal transition dichalcogenides). We report a theoretical forward and experimental results which confirm the possibility of enhancing the effective χ⁽²⁾ of the fiber in a second harmonic generation process.

Tijmen Euser
Optofluidic hollow-core fibres as Raman sensors for Li-ion battery chemistry
E. Miele^1,2, W. M. Dose^2,3, I. Manyakin¹, M. H. Frosz⁴, C. P. Grey², J. J. Baumberg¹, and T. G. Euser^1
1NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, UK
²Department of Chemistry, University of Cambridge, UK
³Department of Engineering, University of Cambridge, Cambridge, UK
⁴Max Planck Institute for the Science of Light, Erlangen, Germany
We demonstrate a fibre-optic sensing method capable of monitoring chemical changes within Li:ion cells under real working conditions. Our technique is based on optofluidic single-ring hollow-core fibres, that uniquely allow light to be guided at the centre of a microfluidic channel. We integrate the fibres into working Li:ion cells, use them to take sub-microliter samples of the electrolyte liquid, and analyse these by background-free Raman spectroscopy to identify early signs of battery degradation.

Goëry Genty
25 years of photonics crystal fibers: Past, present, and future
G. Genty, Tampere University, Finland

Juliano Hayashi
Extruded antiresonant hollow core fibers for mid-IR laser delivery
J. G. Hayashi, A. Ventura, J. Cimek, F. B. Slimen, N. White, H. Sakr, G. T. Jasion, N. V. Wheeler, and F. Poletti
Optoelectronics Research Centre, University of Southampton, UK
We report an overview of our recent progress in the design and fabrication of soft-glass based antiresonant hollow core fibers (AR-HCFs) for laser delivery in the mid-IR (5 – 11 µm). The fibers are fabricated by extrusion and subsequent drawing, using two different glasses: tellurite (70TeO₂-13ZnO-10BaO-7Na₂O), and chalcogenide (IG3, Ge₃₀As₁₃Se₃₂Te₂₅). The fabricated tellurite AR-HCFs can operate from 5 to 7 μm wavelength, and the IG3 AR-HCFs can operate further up to 11 μm wavelength. The numerical and experimental losses of the fundamental mode for the fabricated fibers are on the few dB/m level. Numerical modeling study indicates that, by improving the uniformity and shape of the capillaries, losses down to 0.1 dB/m in the mid-IR (5 to 11 μm) should be possible, making this solution attractive for the mid-IR laser delivery, such CO, CO₂ and quantum-cascade lasers.
Keywords: hollow core fiber, chalcogenide glass, tellurite glass, mid-IR, extrusion.

Kerrianne Harrington
Hollow core optical fibre interconnection and devices
K. Harrington, University of Southampton, UK
Repeatable, mechanically strong and low-loss hollow core fibre interconnections to other photonic devices and optical fibres are critical to realise the unique benefits of these transformative fibres. We report progress on development of novel laser based splicing techniques, micro-collimator based devices and compact micro-optic devices for hollow core fibres.

Piotr Jaworski
Hollow-core microstructured optical fibers assisted spectroscopy of gases in the near- and mid-infrared
P. Jaworski¹, K. Krzempek¹, G. Dudzik¹, P. Kozioł¹, P. Bojęś¹, Fei Yu², Dakun Wu², Meisong Liao², K. Abramski¹, P. J. Sazio³, and W. Belardi^4
1Laser & Fiber Electronics Group, Faculty of Electronics, Wroclaw University of Science and Technology, Poland
²R&D Center of High Power Laser Component, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, China
³Optoelectronics Research Centre, University of Southampton, UK
⁴Université de Lille, CNRS, UMR 8523—PhLAM—Physique des Lasers, Atomes et Molécules, Lille, France
Laser-based gas sensors have been shown to provide excellent capability of detecting various gases, which have their absorption lines in the Near- and Mid-Infrared spectral regions. However, achieving reasonable sensitivity, especially in the case of trace gas detection, is crucial. Enhancement on the sensor detection capacity usually requires the use of bulk-optics-based multipass cells, which increase laser – gas molecules interaction path, however at a cost of significantly reduced stability of the sensor. An alternative solution to provide an increased interaction path is to use a hollow-core fiber, which air-core can be relatively easily filled with any gas analyte. Such gas-filled fiber with potentially any length can serve as a low-volume and robust gas absorption cell. This work presents the application of various hollow-core microstructured fibers for multiple gas detection in the wavelength range spanning from Near- to Mid-Infrared.

Wei Jin
High sensitivity gas detection with microstructured optical fibers
Wei Jin^1,2, Haihong Bao^1,2, Pengcheng Zhao^1,2, Yun Qi^1,2, and Hoi Lut Ho^1,2
1Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong, China
²Photonics Research Centre, The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen, China
We report recent development in laser spectroscopic gas sensing with microstructured hollow-core optical fibres and sub-wavelength-diameter optical nanofibers. The spectroscopic methods employed are photothermal spectroscopy for gases with strong absorption and stimulated Raman gain/dispersion spectroscopy for Raman-active gases. Compared with open-path systems, the use of microstructured optical fibres as sensing elements enables compact all-fibre systems with high performance. With photothermal interferometry, parts-per-billion (ppb) to parts-per-trillion (ppt) level detection of acetylene, methane and ammonia are demonstrated with dynamic range up to seven orders of magnitude. With stimulated Raman spectroscopy, parts-per-million (ppm) level detection of hydrogen is achieved with dynamic range of five orders of magnitude.
Keywords: gas detection, optical fibre sensor, laser spectroscopy, hollow-core optical fibre, microstructured optical fibre, optical nanofibre.

Alexey Kosolapov
Revolver hollow-core optical fibers as a medium for transportation and nonlinear conversion of ultrashort pulses
A. Kosolapov, Fiber Optics Research Center, RAS, Moscow, Russia
Some modes of propagation and nonlinear conversion of subpicosecond pulses in revolver hollow fibers have been investigated. Pulses of 0.8 ps duration and of up to ~ 100 MW power were transmitted along a revolver fiber filled with argon. In the revolver fiber, filled with methane, the stimulated Raman generation of femtosecond pulses was demonstrated. The propagation of an externally excited optical discharge along a revolver fiber filled with air under the action of laser radiation with an intensity well above 1011 W/cm² was studied.

Jesper Laegsgaard
Nonlinear propagation in higher-order modes of microstructured optical fibers
J. Laegsgaard, Technical University of Denmark, Lyngby, Denmark
Higher-order modes (HOMs) offer new opportunities for dispersion engineering in microstructured optical fibers (MOFs), while at the same time HOM properties may be engineered through MOF design. The peculiar modal properties of MOFs makes for interesting differences with step- or graded-index fibers. The talk will discuss simulation techniques for multimode nonlinear propagation in MOFs and show simulation examples of how HOM excitation can enable power scaling of ultrafast nonlinear processes in suitably designed MOFs.

Peter Mosley
Microstructured optical fibre for quantum network interconnects
T. A. Wright, C. Parry, P. B. Main, and P. J. Mosley
Centre for Photonics and Photonic Materials, Department of Physics, University of Bath, UK
Frequency conversion of single photons is a critical to connect quantum-information-processing nodes into large-scale networks for quantum computation and secure communication. Four-wave mixing in photonic crystal fibre (PCF) provides a highly flexible link across a regime of frequency shifts inaccessible to sum- and difference-frequency processes in nonlinear crystals. We present recent experimental results interconverting between a strontium emission line at 1092nm and the telecoms C-band as well as a class of PCF design that enables a single fibre to unify a wide range of source wavelengths in the near infrared.

Jonas Osório
Hollow-core fibers with specific modal operation and low loss in the short wavelength range
J. H. Osório¹, F. Amrani^1,2, F. Delahaye^1,2, F. Giovanardi³, L. Vincetti³, B. Debord^1,2, F. Gérôme^1,2, and F. Benabid^1,2
1GPPMM Group, XLIM Institute, CNRS UMR 7252, University of Limoges, France
²GLOphotonics, Limoges, France
³Departament of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Modena, Italy
We present recent developments on inhibited-coupling hollow-core optical fibers exhibiting specific modal operation and low loss in the short wavelength range. We show that judicious choice of the fiber cladding structure allows obtaining fibers which favors the propagation of higher-order modes and fibers which combines effective single-mode operation and low loss. Moreover, we report on recent improvements in hollow-core fibers with ultralow loss in the visible and ultraviolet range.

Ondřej Podrazký
Double-clad active MOF and shaped optical fibers for fiber lasers and amplifiers
O. Podrazký, A. Jasim, P. Peterka, M. Kamrádek, J. Aubrecht, I. Kašík, and P. Honzátko
Institute of Photonics and Electronics of the Czech Academy of Sciences, Prague, Czech Republic
Double-clad optical fibers (DCFs) allows efficient pumping of fiber lasers and they are indispensable in a design of high-power fiber lasers. While the air cladding offers lowest refractive index and high temperature stability, laser shaping of fiber preforms allows fabrication of fibers with cross-sections which cannot be obtained by mechanical polishing of the preforms. The contribution will present design and fabrication of air-clad DCF and laser shaped DCFs for 2 µm „eye-safe“ region as well as the effects of the fiber cross-section geometry on its performance will be discussed.

Andrey Pryamikov
Vortex supported waveguiding in microstructured optical fibers
A. D. Pryamikov¹ and G. K. Alagashev^2
1A. M. Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia
²D. Mendeleev University of Chemical Technology of Russia, Moscow, Russia
Vortices in the plane can provide transport barriers and decrease losses, as it happens in numerous geophysical, astrophysical flows and in tokamaks. Photon interactions with matter can affect light transport in ways resembling fluid dynamics. Here, we demonstrate significant impact of light vortex formation in micro-structured optical fibres on the energy dissipation. We show possibility of vortex formation in both solid core and hollow core fibres on the zero energy flow lines in the cladding. There is a correlation between appearance of vortices and reduction of light leakage by three orders of magnitude, effectively improving wave guiding.

Aziz Rahman
Modal solution and machine learning: A predictive approach to characterise the photonic crystal fibre
S. Chugh, S. Ghosh, and B. M. A. Rahman
Photonics Department of Electrical and Electronic Engineering, University of London, UK
It is essential to obtain modal solutions of a photonic crystal fibre (PCF) to determine different its optical properties for any potential application. Often a large number of different designs need to be considered for the optimisation before proceeding to its final fabrication and subsequent application. This would require a large amount of data-set to be analysed by using different numerical approaches, such as the widely used finite element frequency domain and finite difference time domain based modal solutions. Here, we present a synergistic approach between numerical modal solutions with an optimised artificial neural network (ANN) which results in a rapid and accurate prediction of all possible optical properties of complex PCFs. As an example, a three hidden layer-based ANN structure is modelled with five input nodes and four output nodes. Basic design parameters, such as, material indices, hole dimensions, pitch, hole orientation and operating wavelengths are considered in the input layer for a simultaneous prediction of PCF effective index, mode effective area, dispersion and confinement loss. This approach shows the potential and benefits of a few seconds of training and testing of an ANN with the previously obtained data over several rigorous simulations of a new complex PCF. We believe this opens a new window in easy determination of optical properties of a photonic crystal fibres before considering their final applications.

Armando Ricciardi
Advanced Lab on Fiber optrodes based on smart materials
A. Ricciardi¹, M. Giaquinto¹, A. Aliberti¹, A. Micco¹, F. Gambino¹, M. Ruvo², and A. Cusano^1
1Optoelectronics Group, Department of Engineering, University of Sannio, Benevento, Italy
²Institute of Biostructure and Bioimaging, National Research Council, Napoli, Italy
The last decade marked a turning point in the optical fiber technology roadmap. The progress in materials science and nanotechnologies turned the Lab on Fiber concept from vision to reality. Thanks to the integration of resonant nanostructures able to confine light at subwavelength scale, optical fibers definitely got new features, thus becoming an exciting "all-around" technological platform. The research on the Lab-on-Fiber technology is currently moving in two main directions. From one hand, novel design criteria involving advanced plasmonic effects are being proposed. On the other hand, further optimization approaches are related to combining standard resonant effects with smart multiresponsive materials (such as microgels). By merging these two approaches at once, it is possible to develop a new class of advanced Lab on Fiber optrodes, with specific application to the life science field. As an example, here we propose an optrode where a multiresponsive microgel film sandwiched between two gold layers is directly integrated on the tip of an optical fiber to form a multifunctional device able to work as an effective sensor for detecting low-molecular weight biomolecules, as well as a fiber-coupled nano-opto-mechanical-actuator triggered by light through thermo-plasmonics effects.
Keywords: Lab-on-Fiber technology, plasmonics, Fabry-Perot, microgels, biosensing, nano-opto-mechanical-actuation.

Martin Rochette
Nonlinear processing with chalcogenide fibers
M. Rochette, Department of Electrical and Computer Engineering, McGill University, Montréal, Canada
This paper provides a short review of the technology and applications of nonlinear chalcogenide fibers. The design principles leading to highly nonlinear chalcogenide microwires and suspended core fibers are reviewed. Nonlinear applications demonstrations of these fibers, such as wavelength conversion and far-detuned amplification, are provided. Future trends of nonlinear chalcogenide fibers are also discussed.

Pier-John Sazio
Active hollow core photonics using composite material ARF waveguides
P. J. A. Sazio¹, A. H. Lewis¹, F. De Lucia¹, Chungche Huang¹, J. R. Hayes¹, F. Poletti¹, D. Hewak¹, and W. Belardi^2
1Optoelectronics Research Centre, University of Southampton, UK
²Université de Lille, CNRS, UMR 8523 –PhLAM – Physique des Lasers Atomes et Molécules, Lille, France
Hollow core waveguides that are able to guide light in the air core such as the anti-resonant fiber (ARF) are becoming increasingly relevant to datacoms, with recent results showing low loss on kilometer scales. Furthermore, the high internal surface area presented by this waveguide geometry offers an ideal materials deposition template for strong light-matter interaction. In this talk we will discuss the development of our functional materials technology to allow for the fabrication of novel composite material anti-resonant fibers (CM-ARFs). As the waveguide properties are theoretically identical to that of a single material ARF with an equivalent refractive index and core wall thickness, only the optical path travelled by light at the core boundary is relevant for antiresonance guidance. This therefore allows us to exploit the active properties of materials selectively added to the basic air-silica design. CM-ARFs therefore allow the otherwise passive photon transport properties of standard ARF air-silica waveguides to be actively managed and controlled. In this talk we will show CM-ARFs created using 300 nm thick silicon layers deposited conformally within an 8-ring tubular borosilicate cladding as well as the incorporation of 2D Transition Metal Dichalcogenide semiconductor materials such as WS2 and MoS₂ layers into cladding voids allows CM-ARFs to act as electro-optical modulators. We record a maximum modulation depth of 3.5 dB at 744 nm, with an average insertion loss of 7.5 dB.

Hanna Stawska
Hollow-core antiresonant fibers – Exploring and enhancing the potential in biochemical detection applications
H. I. Stawska¹, A. Kosolapov², A. Kolyadin², and M. A. Popenda^1
1Department of Telecommunications and Teleinformatics, Wroclaw University of Science and Technology, Poland
²Fiber Optics Research Center of Russian Academy of Sciences, Moscow, Russia
Continuous progress in the fabrication of hollow-core antiresonant fibers (HCARFs) brings new possibilities in developing applications that benefit from their outstanding optical features – low losses, low dispersion and low nonlinearities over several transmission windows. This combination of parameters allows ultrafast signals to be propagated through the fiber without significant distortions, opening the door to a vast range of biochemical applications. In this paper, several different biochemical applications of HCARFs are presented. The starting point was the idea of a completely-fiberized, multiphoton spectroscopy sensor, successfully realized using a single HCARF combined with a fiber microlens tip. The idea was further researched by considering birefringent hollow-core fibers, which eventually yielded a dual-hollow core, antiresonant fiber structure working effectively as a polarization beam splitter. Such structures may find application in methods such as fluorescence anisotropy measurements, which currently are applicable mainly in an in-vitro manner. Additionally, strong dependence of the transmission bands on the refractive index paves the way toward a new kind of refractive index sensors, which can become an important tool in the detection of concentrations of solutions, interactions between immobilized single-strand DNA (ssDNA) and its target or cancer biomarkers. Presented results sum up to a very potent material, presenting the ever-expanding range of applications of HCARFs in the bio-medical sciences, and suggesting that their wide-spread use is about to come.
Keywords: hollow core fibers, antiresonant fibers, microstructured fibers, optical fiber design, optical fiber sensors

Alessio Stefani
Multimaterial and flexible devices made by fiber drawing
A. Stefani^1,2, B. T. Kuhlmey¹, M. C. J. Large¹, J. G. Hayashi³, S. Farajikhah¹, I. D. Rukhlenko¹, A. F. Runge¹, and S. C. Fleming^1
1Institute of Photonics and Optical Science (IPOS), School of Physics, The University of Sydney, Australia
²DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, Kgs. Lyngby, Denmark
³Optoelectronics Research Centre, University of Southampton, UK
The ability to co-process different materials at the same time in a thermal process opens up the possibility to realize volumetric and scalable multimaterial and multifunctional devices with operation spanning from the UV to the microwaves. Combining optical, mechanical and electronical properties of dielectrics (such as glass and polymers) and metals enables a plethora of applications in radiation manipulation. In this presentation I will discuss the process and the challenges of fiber drawing novel materials and material combinations such as: elastic polymers, biocompatible polymers, arsenic free soft-glasses and combinations of metal-dielectric structures. After discussing the process behind the realization of the novel fibers, I will show some very diverse uses of these exotic materials. I will report on our latest results on flexible fibers in generation of orbital angular momentum, realization of tunable metamaterials and wearable sensors, and I will present some applications of fiber drawn metamaterials for THz radiation.

Jim Stone
Optical fibres for healthcare
J. M. Stone, University of Bath, UK
I will discuss our recent developments in the field of optical fibres for healthcare. I will focus on fibre and device design, clinical need and the challenges of getting invasive technologies into clinical trials.

Francesco Tani
Phenomena induced by photoionisation in gas-filled hollow-core photonic crystal fibres
F. Tani¹, J. R. Koehler¹, M. I. Suresh¹, D. Schade¹, F. Köttig¹, and P. St. J. Russell^1,2
1Max Planck Institute for the Science of Light, Erlangen, Germany
²Department of Physics, Friedrich-Alexander-Universität, Erlangen, Germany
The optical properties of hollow-core photonic crystal fibre (HC-PCF) can be conveniently tailored by modifying the transverse microstructure and selecting the species and pressure of the gas filling the hollow regions. Additionally, absorption of light by the gas can result in transient changes in refractive index, with characteristic timescales varying from a few hundred femtoseconds to hundreds of microseconds. Understanding the dynamics of these effects is essential for scaling the power and the repetition rate of laser pulse trains launched into HC-PCF, is relevant for pump-probe experiments, and can suggest new ways of controlling the guiding properties of these fibres. Here we review our recent studies, showing measurements of the temporal evolution of local changes in refractive index and describing the novel experimental techniques we developed to investigate the effects.
Keywords: nonlinear optics, photonic crystal fibres.

Luca Vincetti
Non-idealities in hollow core inhibited coupling fibers
F. Melli¹, F. Giovanardi², L. Rosa¹, and L. Vincetti^1
1Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Modena, Italy
²Department of Engineering and Architecture, University of Parma, Italy
Hollow Core Inhibited Coupling Fibers are experiencing an impressive reduction of their propagation loss. Despite that there is still a difference between experimental loss and the theoretical minimum defined by confinement loss. This difference is assumed to be due to additional loss caused by geometrical irregularities of the real fibers compared to the ideal geometry due to the fabrication process. In this work we numerically investigate additional loss coming from several kinds of geometrical imperfections highlighting their impact in defining fiber total loss.

Isabelle Zaquine
Raman-free fibered photon pair sources
I. Zaquine, Groupe Information Quantique et Applications Département Informatique et Réseaux Télécom Paris, LTCI, Palaiseau, France

 

MOON invited presentations:

Aymeric Arnould
High-speed and ultra-wideband devices for coherent transmission: Challenges and opportunities
A. Arnould, A. Ghazisaeidi, H. Mardoyan, P. Brindel, M. Ionescu, and J. Renaudier
Nokia Bell Labs Paris Saclay, Route de Villejust, Nozay, France
Low cost-per-bit high symbol rate transceivers and link capacity upgrade with ultra-wideband (UWB) amplifiers are promising enabling technologies for future cost-efficient optical networks. In this paper, we review recent progress and expectations in high-speed CMOS digital-to-analog (DAC) converters in the generation of 100 GBd class signals and semiconductor optical amplifier (SOA)-based UWB repeaters to extend the transmission bandwidth up to 100 nm.

Nicola Calabretta
High extinction ratio and low crosstalk C and L-band photonic integrated wavelength selective switching
R. Magalhães Gomes Kraemer¹, F. Nakamura², Yu Wang¹, H. Tsuda², and N. Calabretta^1
1IPI-ECO Research Institute, Eindhoven University of Technology, the Netherlands
²Graduate School of Science and Technology, Keio University, Yokohama, Japan
A photonic integrated 1x2 Wavelength Selective Switch (WSS) based on a loopback configuration is shown to operate on the C and L-Bands due to the cyclic nature of the employed arrayed-waveguide gratings (AWGs). The photonic integrated circuits is capable to switch and separate channels in the C and L bands to one of the two output ports in order to implement a low cost 2 degree ROADMs for metro-access applications.
Keywords: wavelength selective switch, optical multiband, arrayed-waveguide gratings, photonic switch.

Cecilia Clivati
Coherent interferometry over telecom networks for time-frequency distribution and geophysical sensing
C. Clivati, A. Mura, V. Kuttippurath, F. Levi, and D. Calonico
Istituto Nazionale di Ricerca Metrologica- INRIM, Turin, Italy
In the last decade, fiber networks for telecommunication have started to be exploited in a metrological context, for the distribution of accurate time-frequency signal to both research institutes and commercial partners. Time and frequency distribution over fiber is nowadays enabling most of high-resolution comparisons of atomic clocks between distant Metrological Institutes all over Europe and has been adopted in other fields both in fundamental and applied science. Recently, we demonstrated that the same technique can be used to detect weak earthquakes and other acoustic phenomena. This raised strong interest in the geophysical community, especially in view of its exploitation in seas and oceans, where currently no sensors are available. Our contribution describes the basics of technique and achieved results, with particular attention to geophysical applications, and future perspectives.
Keywords: frequency metrology, coherent interferometry, geophysical sensing, distributed acoustic sensing.

Vittorio Curri
Software-defined WDM optical transport in disaggregated open optical networks (Keynote)
V. Curri, DET, Politecnico di Torino, Italy
With the introduction of coherent optical technologies, at the end of the first decade of 2000s, optical networks have radically transformed their nature. Using of 10G channels exploiting intensity-modulation with direct detection (IMDD), besides limiting the overall capacity of optical line systems, strongly prevented the capability of lightpath transparent routing, because of the in-line dispersion-compensation units (DCU) needed by the IMDD to operate at the optimal dispersion map. Moreover, IMDD transceivers did not include any digital signal processing (DSP) unit and consequently did not have autonomous channel equalization capabilities. So, line systems supporting WDM optical data transport were closed systems with very-limited reconfigurability over their lifetime. It implied the exploitation of data transport by networking management as a closed commodity, practically impeding physical layer aware networking, for planning, signaling, control and restoration. Polarization-division-multiplexed multilevel modulation formats exploiting DSP-based coherent transceivers – the so-called coherent optical technologies – have radically mutated the paradigm. Thanks to DSP, transceiver operations are software-defined and blind channel equalizers are implemented. So, lightpaths can be transparently routed over the network topology by ROADM nodes and the deployed lightpath rate can be adapted to the available quality-of-transmission (QoT). Also, lines do not need any more DCUs, simplifying design, management and maintenance. In such a scenario, physical mechanisms impairing transmission have permitted to develop simple yet effective mathematical models, and consequent software implementations. Each lightpath can be modeled as an additive and Gaussian nonlinear channel, where the overall noise is the sum the ASE noise introduced by each amplifying site plus the nonlinear interference (NLI) generated by each fiber span due to the nonlinear crosstalk among the active lightpaths. It means that the QoT for WDM data transport can be summarized by the signal-to-noise ratio, that because of the nonlinear term is called generalized SNR, or GSNR. Such a novel paradigm, enables a simple abstraction of physical layer, as a graph weighted by the GSNR impairment of each line-system and by the filtering penalties of switches. By relying on such an abstraction, the control plane may dynamically operate the physical layer aiming at the optimal multilayer orchestration. In this work, we summarize the physical model for WDM optical transport of coherent optical technologies addressing the issues related to the ASE noise and models for NLI generation, as well as the need for properly considering the stimulated Raman scattering in case of line systems exceeding the C-band. Then, we’ll comment on the software implementation of a quick and accurate QoT estimator (QoT-E) referring to the results obtained by the Telecom Infraproject with the GNPy open-source project. We’ll show some validation results and comment on the perspectives in the interaction with network planning, control and signaling.
The presented results and concepts have been developed within the OOPT-PSE working group of the consortium Telecom Infraproject (https://telecominfraproject.com/oopt/).

Vittorio Curri
Multi-band and multi-service open optical networks: Applications and perspectives
V. Curri, DET, Politecnico di Torino, Italy
Since 1990s, optical fiber cables have been extensively installed, first to implement ultra-long-haul submarine links, then for the development of high-capacity terrestrial back-bone networks, and recently for the development of metro- and access networks as well as for data-center interconnect and 5G front- and back-hauling. The development of fiber infrastructures is still in-progress and accelerating, mostly in north-America and east-Asia, but also in European countries, as for instance in Italy. Thus, in near future, we’ll rely on an installed worldwide glass-web that will enable ultra-high capacity Internet as well as additional services. Besides the availability of the optical infrastructures, the full exploitation of the glass-web will need to implementing the openness paradigm, to enable multiple-player interoperability on optical infrastructures. In this work, we will review the physics of optical transmission over the up to 50 THz low-loss and single-mode bandwidth of single-mode optical fibers, that enables an effective and accurate software abstraction of optical transmission. We’ll also review how the optical fiber is sensible to the mechanical stresses that modify propagation properties, so enabling the use of dedicated fibers as distributed acoustic sensors (DAS). Then, we’ll analyze how the physical layer abstraction can be used to control and manage open and disaggregated optical networks, also enabling the optimal exploitation of additional transmission bandwidths besides the C-band. We’ll also discuss on the possibility to exploit spectral portions to transport signals alternative to data signals, and in particular time and frequency distribution, that are becoming crucial services for finance markets and 5G network synchronization. Finally, we’ll address the possibility to exploit optical network infrastructures also for DAS together with data transport.

Yvan Pointurier
Machine learning-aided quality of transmission (QoT) estimation
Y. Pointurier, Huawei Technologies, Paris Research Center, Boulogne-Billancourt, France
In this talk, I will review methods to improve prediction of Quality of Transmission tools in optical networks using machine-learning based techniques, either as an aid or even a replacement for the traditional physical models. Pros and cons of the various techniques proposed so far will be discussed.

Nicola Sambo
Beyond C-band in optical networks
N. Sambo¹, A. Ferrari², A. Napoli³, N. Costa⁴, J. Pedro⁴, B. Sommerkorn-Krombholz³, P. Castoldi¹, and V. Curri^2
1Scuola Superiore Sant’Anna, Pisa, Italy
²Politecnico di Torino, Torino, Italy
³Infinera, Munich, Germany
⁴Infinera Unipessoal Lda., Carnaxide, Portugal
This paper investigates provisioning in multi-band optical networks. Physical impairments arising from the activation of wide spectrum are taken into account through the generalized Gaussian Noise model. Simulations show that most potentials are attained by exploiting S and E bands. Insights are provided about the enabling technology.
Keywords: multi-band, QoT, RSA, multi-band transmission.

Matheus Sena
Performance evaluation of InP-based DP-IQ modulators for multiband transmission systems
M. Sena¹, Y. Cui¹, G. Fiol¹, B. Shariati¹, A. Napoli², J. K. Fischer¹, M. Schell¹, and R. Freund^1
1Fraunhofer-Institut für Nachrichtentechnik, Heinrich-Hertz-Institut, Berlin, Germany
^2Infinera, Munich, Germany
In this paper we study the wavelength-dependence of power imbalance and insertion loss in InP-based 2×2 Multi-Mode Interference (MMI) couplers as means to evaluate the design of multiband DP-IQ modulators. A system level investigation is performed on a simulated coherent transmission setup and the impact of different MMI design strategies for 4- and 16-ary quadrature amplitude modulation (QAM) signals is studied.
Keywords: multiband, InP modulator, MMI, coherent optics.

Emanuele Virgillito
Non-linear SNR degradation of mixed 10G/100G transmission over dispersion-managed networks
E. Virgillito¹, S. Straullu², A. Castoldi³, R. Pastorelli³, and V. Curri^1
1DET, Politecnico di Torino, Italy
²LINKS Foundation, Torino, Italy
³SM-Optics, Vimercate, Italy
Enabling the mixed 10G IMDD with 100G coherent channels transmission over legacy dispersion-managed links on metro network chunks will come in handy for the operators to increase network flexibility while saving on CAPEX and operate progressive upgrades with no impact on existing traffic. We developed a semi-analytical model for 10G-to-100G XPM noise allowing QoT estimation on mixed 10G/100G systems.

 

MWP invited presentations:

Hercules Andrianopoulos
Optical beamforming networks supporting multibeam and multicast operation
C. Tsokos¹, E. Andrianopoulos¹, A. Raptakis¹, N. Lyras¹, L. Gounaridis¹, P. Groumas^1,2, H. Avramopoulos¹, and Ch. Kouloumentas^1,2
1National Technical University of Athens, Greece
²3Optagon Photonics, Greece
We assess the performance of two optical beamforming networks (OBFNs) able to support multibeam and multicast operation in wireless systems. Assuming operation in the downlink direction, these networks are based on reconfigurable optical matrices that have the ability to transmit up to M different information signals, by feeding an N-element antenna array with the appropriate excitation signals. Each transmitted signal can be steered independently either to a single angle, in the case of multibeam operation, or to different angles in the case of multicast operation, by properly tuning the phase and the amplitude relationships of the excitation signals. The first OBFN is based on the use of an MxN optical Blass matrix architecture. Each node of the matrix relies on the use of an optical phase shifter and a Mach-Zehnder Interferometer which tune the phase and the amplitude of the optical signals with respect to the beamforming parameters and the mode of operation. The second OBFN uses wavelength division multiplexing techniques to form the signals that correspond to each antenna element, and a matrix comprising of optical delay lines and optical attenuators for the processing of the corresponding optical signals. In this paper, we present the required optical techniques for the use of the two OBFNs in both operation modes and through simulation studies, we assess their beamforming performance at 28.5 GHz with respect to the number of the antenna elements, modulation order, symbol rate and pulse shaping parameters. The evaluation of the performance of the OBFNs is performed through the off-line calculation of the bit-error-rate (BER) of the received signals at the corresponding observation angles. In addition, regarding the second architecture, we experimentally validate its proof of concept, when operating in the multicast mode using an OBFN based on commercially available components.

Antonella Bogoni
Photonics enabling coherent MIMO radar networks
F. Scotti¹, A. Malacarne², S. Maresca², P. Ghelfi¹, G. Serafino², and A. Bogoni^2
1Consorzio Nazionale Interuniversitario per le Telecomunicazioni (CNIT), Pisa, Italy
²Scuola Superiore di Studi Universitari e di Perfezionamento Sant’Anna, Pisa, Italy
The potential of coherent MIMO radar networks enabled by photonics is introduced. The first coherent dual-band 2x4 MIMO radar experiment is presented. Range/cross-range maps demonstrate the higher cross-range resolution due to the coherence and the enhanced performance introduced by dual-band operation.

Antonella D'Orazio
Additive manufacturing for 5G antennas: How technologies and materials impact on design
V. Marrocco¹, V. Basile¹, M. Grande², F. Prudenzano², I. Fassi³, and A. D’Orazio^2
1STIIMA CNR, Institute of Intelligent Industrial Technologies and Systems for Advanced Manufacturing, National Research Council, Bari, Italy
²Politecnico di Bari, Italy
³STIIMA CNR, Institute of Intelligent Industrial Technologies and Systems for Advanced Manufacturing, National Research Council, Milan, Italy
Additive Manufacturing (AM) has recently proved its feasibility for the fabrication of compact electronic and telecommunication components with high level of customization. Compared to conventional manufacturing technologies, AM exhibits the dramatic capability of rapid prototyping parts and devices fast and at reasonable costs. In order to have a clear view about the way AM is developing into recent and future telecommunication contexts, the present work will show the most recent antenna design for 5G communications, highlighting the use of AM solutions for the antenna fabrication. To this aim, 3D-shaped dielectric resonator antennas (DRAs) were designed and fabricated, pointing out the role played on the DRA performance by the chosen fabrication technique. Two AM technologies are investigated in terms of usable materials, surface quality and dimensional accuracy of the produced device. Relevant results concerning the effects induced by fused deposition modelling (FDM) and stereolithography (SLA) on the scattering parameter S₁₁ and gain of 3D-DRA designs are illustrated and discussed.
Keywords: dielectric resonator antenna, 5G communications, additive manufacturing, fused deposition modelling, stereolithography.

Paolo Ghelfi
Towards an integrated photonics-based radar
P. Ghelfi¹, F. Scotti¹, F. Falconi², C. Porzi², S. Melo², and A. Bogoni^1,2
1PNTLab, CNIT, Pisa, Italy
²TECIP Institute, Scuola Superiore Sant’Anna, Pisa, Italy
The paper reviews the recent activities towards the implementation of a photonics-based radar as a packaged integrated photonic device. Recent experimental results are presented, obtained with a radar implemented as a photonic integrated circuit in a Silicon-on-Insulator platform. The potentials and open issues of using photonic integration and its related packaging for flexible radar systems are also discussed.
Keywords: microwave photonics, radar, photonic integration.

Stavros Iezekiel
Optically controlled leaky-wave antenna based on NRI-TL metamaterials
K. Neophytou¹, A. Kanno², M. A. Antoniades¹, and S. Iezekiel^1
1EMPHASIS Research Centre, University of Cyprus, Nicosia, Cyprus
²National Institute of Information and Communications Technology (NICT), Koganei, Tokyo, Japan
We propose the optical control of a negative refractive index transmission-line leaky-wave antenna. This is achieved by implementing optically controlled varactors in the unit cell structures of a negative-refractive-index-transmission-line leaky-wave antenna. An indirect optical scheme is used in which the varactor drive voltage is obtained from a photodiode/transimpedance amplifier combination. This enables us to control the time delay of each negative-refractive index-transmission-line unit-cell and therefore steer the radiation beam of the leaky-wave antenna.

Carmo Medeiros
Evaluation of beam squint effects on beam forming supported by Mach-Zehnder Interferometer
A. E. R. C. Santos and M. C. R. Medeiros
IT-Instituto de Telecomunicações – Pólo de Coimbra, Departamento de Engenharia Eletrotécnica e de Computadores, Universidade de Coimbra, Portugal
Beam forming is considered of key importance for the fifth generation (5G) of mobile networks, particularly for millimeter wave (mmWave) operation, where blockage effect, propagation loss and high directionality requires sharp directional beams. Phased array antennas (PAA) that consists of an array of multiple antenna elements (AEs), enable beam forming that traditionally relies on microwave phase shifters which are used to control the phase of each AE. Microwave electrical phase shifters suffer from beams quint problem which limits the operation bandwidth. This problem can be alleviated by photonic supported beam forming strategies such as the ones based on Mach-Zehnder interferometers (MZI). However, MZIs do not provide true time delay for a large bandwidth signals and therefore residual beam can impair the system performance. In this paper we analyze, by simulation, the performance degradation effects of the residual beam squint of MZI based beam forming strategies for high bandwidth Orthogonal Frequency Division Multiplexing (OFDM) signals.

Robert Minasian
Advances in microwave photonic signal processing and sensing
R. Minasian and Xiaoke Yi
University of Sydney, Australia
Photonic signal processing offers the prospect of overcoming a range of challenging problems in the processing of high-speed signals. Its intrinsic advantages of high time-bandwidth product and immunity to electromagnetic interference (EMI) have led to diverse applications. Photonic signal processing leverages the advantages of the optical domain to benefit from the wide bandwidth, low loss, and natural EMI immunity that photonics offers. Next generation and emerging applications in radar, communications and precision sensing will require entirely new technologies to address the current limitations of electronics. Microwave photonics, which merges the worlds of RF and photonics, shows strong potential as a key enabling technology to obtain new paradigms in the processing of high speed signals that can overcome inherent electronic limitations. In addition, the growth of silicon photonics provides a platform for integration together with CMOS electronics, to obtain future signal processing systems that can implement high bandwidth, fast and complex functionalities. Recent advances in microwave photonic signal processing are presented. These include versatile photonic-assisted scanning receivers for high-speed microwave frequency measurement of unknown signals, and high-resolution microwave photonic sensing systems. These microwave photonic processors provide new capabilities for the realisation of high-performance signal processing and sensing.

Diego Perez-Galacho
New approaches for the generation and transmission of analog radio over fiber links
D. Perez-Galacho, E. Briceño-Sanchez, and S. Sales
ITEAM Research Institute, Universitat Politècnica de València, Spain
The current and future demand for IP traffic and wireless connection requires the development of technologies that allow to meet the needs anticipated in the coming years. Since 2015, when ITU started the work to establish the concepts of the new generation of mobile networks, new features and technologies have been incorporated by organizations such as IEEE or 3GPP in order to establish a concise standardization of the future 5G. The cornerstone of 5G technology is the use of small cells in the access network, as well as the use of high frequencies for broadcasting, these aspects provide a solution to increase the capacity of the system. In this work, we will present our recent advances in the generation of mmWave signals for 5G using Microwave Photonics.

 

NAON invited presentations:

Dimitris Alexandropoulos
Study of the dynamics of spin-polarized vertical cavity surface emitting lasers using largest Lyapunov exponent
P. D. Georgiou¹, D. Alexandropoulos¹, and C. Skokos^2
1Department of Materials Science, University of Patras, Greece
²Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch, South Africa
Polarization dynamics of spin polarized Vertical Cavity Surface Emitting Lasers (VCSELs) has been the subject of intense research work. Apart from the interesting physics involved, polarization dynamics of VCSELs offer a platform for a wide range of applications. Recently, the potential of the use of Quantum Dot (QD) VCSELs has been highlighted. Regardless of the active material, reliable resolution of the dynamics is important. Two methods are primarily used, namely Bifurcation Theory (BT) and the Largest Lyapunov Exponent (LLE). Among the two, BT is more popular within the optoelectronics community by virtue of its simplicity. The method can determine in a fast and trackable manner the kind of the nonlinear dynamics. However, it cannot quantify the strength of nonlinear dynamics. This is possible with the LLE method which can be beneficial in some cases where an asymmetry in the dynamics of the system might exist. Our recent work on the dynamics of spin polarized QD-VCSELs that accounts for both the effects of Ground States (GS) and Excited States (ES) has concluded that the time evolution of the ES and GS is asymmetric. BT is agnostic to time evolution and hence, the phenomenon can only be identified by means of LLE. In the present contribution we will review the use of the LLE method in the study of polarization dynamics of VCSELs and highlight the benefits of quantification of the dynamics in the case of QD-VCSELs.

Hovik Baghdasaryan
Optical tunneling at frustrated total internal reflection: Revisited with the wavelength-scale analysis by the method of single expression
H. V. Baghdasaryan¹, T. M. Knyazyan¹, T. T. Hovhannisyan¹, G. R. Mardoyan², and M. Marciniak^3
1National Polytechnic University of Armenia, Yerevan, Armenia
²National Instruments AM LLC, Yerevan, Armenia
³National Institute of Telecommunications, Warsaw, Poland
Frustrated total internal reflection is the well-known and practically important phenomenon when at oblique incidence of optical wave on an optical barrier the light is partly transmitted through the barrier. An optical barrier is called a confined medium where only evanescent amplitude of optical wave (evanescent waves) can exist. The method of single expression permits to observe optical energy flow (Poynting vector) not only outside of an optical barrier, but also within the barrier, i.e. in the region of evanescent waves. Percolation of optical energy through the barrier at oblique incidence of TE and TM waves is analyzed.

Yossef Ben-Ezra
High spectral efficiency (SE) analogous optical link (AOL) with a quantum dot (QD) laser operating in the excited state (ES)
Y. Ben Ezra and B.I. Lembrikov
Faculty of Electrical Engineering and Electronics, Holon Institute of Technology, Israel
Semiconductor quantum dot (QD) lasers are characterized by ultrafast dynamics, low threshold, temperature stability, large spectral bandwidth, low energy consumption, compatibility with modern micro- and nanotechnologies [1]-[3]. They can be used in modern optical communication systems due to these unique properties caused by the 3D confinement of carriers in QDs [1]-[3]. The energy level structure of QDs is described by the continuous carrier reservoir wetting layer (WL), the ground state (GS) and the excited state (ES) levels [1]-[3]. Typically, for the moderate operation rates and comparatively low bias current the QD laser dynamics is determined by the transitions between WL and GS while the fast ES-GS transitions can be neglected [3]. The QD laser performance in an ultra-wideband (UWB) analogous optical link (AOL) has been investigated theoretically by using the GS lasing model [4]. However, the ES emission should be taken into account for a high enough bias current [5], [6]. In such a case, the QD lasers first simultaneously emit in the GS and ES, and then for the bias current high enough the QD lasers may emit in the ES only [7]. ES-QD lasers demonstrate higher differential gain, a smaller relaxation oscillation (RO) damping rate, the enhanced modulation response, the broad modulation bandwidth and low chirp-to-power ratio [7]. We investigated theoretically the ES lasing influence on the QD-in-a-well (QDWELL) laser performance in optical communication systems for the case of the 4 level pulse amplitude modulation (4-PAM) and 8 level PAM (8-PAM) formats [8]. It has been shown that the ES radiation substantially increased the QDWELL laser modulation bandwidth for the advanced modulation formats 4-PAM and 8-PAM up to the bit rate of 16 Gb/s [8]. In this paper, we studied theoretically the influence of the ES-QD laser on the performance of the high spectral efficiency (SE) radio-over-fiber (RoF) AOL for the case of the direct detection (DD) orthogonal frequency division multiplexing (OFDM) and modulation formats of 16 quadrature amplitude modulation (16QAM), 64QAM and 256QAM. In particular, high SE AOLs based on the RoF technology are the promising candidates for the 5 generation (5G) mobile networks where the low latency, large bandwidth, high data transfer rate, and the energy efficiency of the network are required [9], [10].
Keywords: optical communications, quantum dot (QD), QD laser, analogous optical link (AOL).
[1] E. U. Rafailov, M.A. Cataluna, E.A. Avrutin. Ultrafast Lasers based on Quantum Dot Structures. Wiley, 2011.
[2] V.M. Ustinov, A.E. Zhukov, A. Yu. Egorov, N.A. Maleev. Quantum Dot Lasers. Oxford University Press, 2003.
[3] K. Lüdge. Modeling quantum-dot-based devices. In: Nonlinear Laser Dynamics. Edited by K. Lüdge. Wiley, 2012, 3-33.
[4] Y. Ben Ezra, B.I. Lembrikov, UWB system optical link based on a quantum-dot-in-a-well (QDWELL) laser, Optical and Quantum Electronics, vol. 47, no. 6, pp. 1527-1533, Jun. 2015.
[5] Cheng Wang, B. Lingnau, K. Lüdge, J. Even, and F. Grillot. Enhanced dynamic performance of quantum dot semiconductor lasers operating on the excited state. IEEE Journal of Quantum Electronics, vol. 50, no. 9, pp. 723-731, Sep. 2014.
[6] A. Röhm, B. Lingnau, K. Lüdge. Understanding ground-state quenching in quantum-dot lasers. IEEE Journal of Quantum Electronics, vol. 51, no. 1, 2000211-1-11, Jan. 2015.
[7] Zai-Fu Jiang, Zheng-Mao Wu, E. Jayaprasath, Wen-Yan Yang, Chun-Xia Hu and Guang-Qiong Xia. Nonlinear dynamics of exclusive excited-state emission quantum dot lasers under optical injection. Photonics, vol. 6. no. 58, pp. 1-11, 2019.
[8] Y. Ben Ezra and B.I. Lembrikov. The influence of the excited state (ES) lasing in quantum dot-in-a-well (QDWELL) structure on the QDWELL laser performance in optical communication systems. 21th Int'l. Conf. on Transparent Optical Networks (ICTON 2019), Angers, France, paperWe.E4.1.
[9] Sara S. Jawad, Raad S. Fyath. Transmission performance of analog radio-over-fiber fronthaul for 5G mobile networks. International Journal of Networks and Communications, vol. 8, no. 3, pp. 81-96, 2018.
[10] Khan Zeb, Xiupu Zhang, and Zhenguo Lu. High capacity mode division multiplexing based MIMO enabled all-optical analog millimeter-wave over fiber fronthaul architecture for 5G and beyond. IEEE Access, vol. 7, pp. 89522-89533, 2019.

Pascal Landais
Expanded optical frequency comb generation using a gain switched self-seeded passive feedback laser
M. N. Hammad¹, E. P. Martin¹, S. T. Ahmad¹, A. Kaszubowska-Anandarajah², P. M. Anandarajah¹, and P. Landais^1
1Photonics Systems and Sensing lab., School of Electronic Engineering, Dublin City University, Ireland
²CONNECT Research Centre, Dunlop Oriel House, Trinity College Dublin, Ireland
In this paper, an expanded optical frequency comb (OFC) using a gain-switched self-seeded passive feedback laser (PFL), is presented. The device consists of two sections comprising an active distributed feedback (DFB) section and a passive integrated feedback (IFB) section, providing an on-chip injection to the active DFB section. Optimising the feedback from the IFB section results in an expansion of the number of generated OFC lines. As each comb line can be used as a distinct data carrier, the ability to boost the number of tones results in an increase in the overall data rate that can be transmitted using a single OFC. The paper presents a characterisation of important parameters of the laser, such as phase noise and linewidth, both in continuous wave (CW) and gain-switched mode operations. The effect of varying the phase shift of the feedback signal, through varying the bias applied to the IFB section, is also examined. The results show that by optimising the feedback signal, an expanded OFC can be generated.
Keywords: passive feedback laser, optical frequency combs, gain switching, phase noise, linewidth.

Nikolay Ledentsov
Edge- and surface-emitting lasers applying TM mode confined at the distributed Bragg reflector-air interface
N. N. Ledentsov¹, V. A. Shchukin¹, V. P. Kalosha¹, N. Ledentsov, Jr.^1,2, L. Chorchos^1,2, and O. Makarov^1
1VI Systems GmbH, Berlin, Germany
²Warsaw University of Technology, Poland
A novel concept of a wavelength-stabilized laser utilizes TM mode trapped at the interface between the distributed Bragg reflector (DBR) and the air at a wavelength matching approximately the middle of the stopband range at the angle of the total internal reflection [1]. The wavelength can be tuned by modifying the thickness and the composition of the top DBR layer or by replacing air with another material having a refractive index lower than that in the DBR layers. In vertical cavity surface emitting lasers (VCSELs) such mode can have the same wavelength as the VCSEL mode. In such case an enhanced lateral leakage of high order transverse modes outside of the aperture is possible. VCSELs with a gradient in the oxide-confined aperture diameter (3-5 µm) across the wafer are studied and demonstrate predominantly fundamental mode lasing with oscillatory behavior in the side mode suppression ratio (SMSR) between 7 and 30 dB as a function of the aperture diameter in line with the theoretical expectations [2]. A multimode fiber transmission at 25 Gb/s over 1.4 km distance is demonstrated.
[1] V. A. Shchukin, N. N. Ledentsov, and A. Yu. Egorov, “Wavelength-stabilized near-field laser,” Opt. Express 27(22), 32019-32036 (2019).
[2] V. Kalosha, V. A. Shchukin, N. Ledentsov Jr., J.-R. Kropp, and N. Ledentsov, “Robustness versus thermal effects of single-mode operation of vertical-cavity surface-emitting lasers with engineered leakage of high-order transverse optical modes,” Proc. SPIE 10122, Vertical-Cavity Surface-Emitting Lasers XXI, 10122-19 (2017).

Radu Malureanu
An overview of ultra-thin films in nanophotonics and their applicability
R. Malureanu¹, J. Sukham^1,2, S. Köse^1,3, O. Takayama¹, and A. Lavrinenko^1
1Technical University of Denmark, Department of Photonics Engineering, Lyngby, Denmark
²Center for Nanophotonics, AMOLF, Amsterdam, Netherlands
³Delft University of Technology, Faculty of Applied Sciences, Delft, Netherlands
In this paper, we will present an overview of the challenges encountered when depositing and patterning ultra-thin metallic films as well as multi-layered structures and the various ways used to overcome them. Gold is one of the most used metallic layers for nanophotonics. Currently, the minimum thickness of a continuous Au layer without any adhesion improvement is down to 2 nm, using deposition at cryogenic temperatures. For room-temperature depositions, the limit without adhesion layers is in the range of 15 nm. Using organic adhesion layers, the minimum thickness is 6 nm while with metallic adhesion layers it can be lowered to 3 nm. Each technique comes with advantages and disadvantages that will be discussed during the presentation. The other mostly used metal in nanophotonics is silver, due to its lower value of imaginary part of the dielectric permittivity. However, silver is highly oxidizing, making it generally unsuitable for long-term use. Initial experiments using a mixture of Ag and Al, with low Al content, have been performed to increase the layer’s long term stability. Dielectric layers can be deposited using a variety of techniques. The most precise among them is the atomic layer deposition technique (ALD) that allows control of the thickness at monoatomic layer level. Combining the two techniques, multilayer structures comprised of metals and dielectrics can be obtained. Within our lab, we created structures up to 10 periods of Au and Al₂O₃ layers and we showed the onset of effective material properties within those structures. As well, using physical bombardment in an ion beam etching machine, we have patterned structures having 3 periods, with relatively low sidewall roughness and sidewall angle reaching 60 degrees. These results and a comparison to the ones available in literature will be presented during the conference.
Keywords: ultra-thin Au layers, Ag-Al layers, hyperbolic metamaterials, multilayer patterning.

Alexander Quandt
Waveguide arrays and optical analogies
A. Quandt¹, C. Pelwan¹, and R. Warmbier^2
1School of Physics, DST-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, Johannesburg, South Africa
²Department of Physics, University of Johannesburg, South Africa
There are obvious similarities between the Schrödinger equation and the paraxial wave equation used to describe light waves propagating through an optical waveguide. These similarities can be exploited in optical waveguide arrays to fabricated optical analogues of basic Schrödinger operators. Thus, the fundamental physics of these model systems can be explored in great detail using standard optical equipment. We will give some illustrative examples, like the optical analogues of topological phases, unusual photonic band structures, and the study of rogue waves based on to the nonlinear Schrödinger equation.

Ana Quirce
Nonlinear dynamics of optical frequency combs generated by gain-switched semiconductor lasers subject to optical injection
A. Quirce¹, A. Rosado², J. Díez³, A. Pérez-Serrano², J. M. G. Tijero², A. Valle³, L. Pesquera³, and I. Esquivias^2
1Vrije Universiteit Brussel, Brussels Photonics B-PHOT, Belgium
²CEMDATIC-E.T.S. I Telecomunicación, Universidad Politécnica de Madrid (UPM), Spain
³Instituto de Física de Cantabria (CSIC-University of Cantabria), Santander, Spain
We report an experimental study of the nonlinear dynamics appearing when an optical frequency comb (OFC) generated by a gain-switched discrete mode laser (DML) is subject to optical injection. OFCs with a frequency spacing of f_m=5 GHz were generated for two different values of the modulation amplitude. For low injected power two combs due to the gain-switched DML and the injected field are observed with the same frequency spacing. When the injected power is increased for a fixed value of the frequency detuning, a rich variety of nonlinear behaviour was found. Irregular behaviour, limit cycles or locked combs with a frequency spacing of f_m/2, f_m/3 among others are obtained. A much more complex dynamics was found for the lowest modulation amplitude.
Keywords: optical frequency combs, discrete mode lasers, gain switching, optical injection, nonlinear dynamics.

Edik Rafailov
Short pulse generation from optically and electrically pumped VECSELs
E. U. Rafailov, Aston University, Birmingham, UK
Passive mode-locking of optically-pumped (OP) and electrically-pumped (EP) VECSELs has enabled the generation of ultrashort pulses from mass-producible, low-cost laser sources. Mode-locked VECSELs provide output pulses with durations of few hundreds femtoseconds, energies of up to tens of picojoules, and repetition rates of several GHz. Due to the ease of integration into optoelectronic devices, diffraction-limited beam profiles, and peak powers of multiple watts, mode-locked VECSELs have become promising ultrafast laser sources for biomedical applications. We will present a review of the research results obtained since the first demonstration of a passively mode-locked VECSEL. This includes an overview of the state-of-the-art in terms of laser performance and pulse characteristics. Additionally, we will discuss different laser designs and mode-locking techniques, covering SESAM and SESAM-free mode-locking and approaches for pulse duration and energy scaling. A summary of observed mode-locked regimes will be provided. Finally, a brief outline of current research activity and future perspectives in the field of mode-locked VECSELs will be presented.

Judy Rorison
Giant bowing of the bandgap and spin-orbit splitting in GaP_1-xBi_x dilute bismide alloys
Z. L. Bushell¹, C. A. Broderick^2,3, L. Nattermann⁴, R. Joseph¹, J. L. Keddie¹, J. M. Rorison³, K. Volz⁴, and S. J. Sweeney^1
1Advanced Technology Institute and Department of Physics, University of Surrey, Guildford, UK
²Tyndall National Institute, Cork, Ireland
³Department of Electrical and Electronic Engineering, University of Bristol, UK
⁴Materials Science Center and Faculty of Physics, Philipps-Universität Marburg, Germany
Using spectroscopic ellipsometry measurements on GaP_1−xBi_x/GaP epitaxial layers up to x = 3.7% we observe a giant bowing of the direct band gap (E_g^Γ) and valence band spin-orbit splitting energy (Δ_SO). E^Γ_g (Δ_SO) is measured to decrease (increase) by approximately 200 meV (240 meV) with the incorporation of 1% Bi, corresponding to a greater than fourfold increase in Δ_SO in going from GaP to GaP_0.99Bi_0.01.The evolution of E_g^Γ and Δ_SO with x is characterised by strong, composition-dependent bowing. We demonstrate that a simple valence band-anti-crossing model, parametrised directly from atomistic supercell calculations, quantitatively describes the measured evolution of E_g^Γ and Δ_SO with x. In contrast to the well-studied GaAs_1−xBi_x alloy, in GaP_1−xBi_x substitutional Bi creates localised impurity states lying energetically within the GaP host matrix band gap. This leads to the emergence of an optically active band of Bi-hybridised states, accounting for the overall large bowing of E_g^Γ and Δ_SO and in particular for the giant bowing observed for x ≲ 1%. Our analysis provides insight into the action of Bi as an isovalent impurity, and constitutes the first detailed experimental and theoretical analysis of the GaP_1−xBi_x alloy.

Michael Scalora
Electrodynamics of conductive oxides: Intensity-dependent anisotropy, reconstruction of the effective dielectric constant, and harmonic generation
M. Scalora¹, J. Trull², M. A. Vincenti³, D. de Ceglia⁴, Z. Coppens⁵, N. Akozbek⁵, L. Rodriguez Sune², and C. Cojocaru^2
1Charles M. Bowden Research Center, AMRDEC, RDECOM, Redstone Arsenal, AL , USA
²Universitat Politècnica de Catalunya, Physics Department, Terrassa, Barcelona, Spain
³Department of Information Engineering – University of Brescia, Brescia, Italy
⁴Department of Information Engineering – University of Padova, Italy
⁵AEgis Technologies Inc., Huntsville, AL USA
We study electromagnetic pulse propagation in an indium tin oxide nanolayer in the linear and nonlinear regimes. We use the constitutive relations to reconstruct the effective dielectric constant of the medium, and show that nonlocal effects induce additional absorption resonances and anisotropic dielectric response: longitudinal and transverse effective dielectric functions are modulated differently along the propagation direction, and display different epsilon-near-zero crossing points with a discrepancy that increases with increasing intensity. We predict that hot carriers induce a dynamic redshift of the plasma frequency and a corresponding translation of the effective nonlinear dispersion curves that can be used to predict and quantify nonlinear refractive index changes as a function of incident laser peak power density. Our results suggest that large, nonlinear refractive index changes can occur without the need for epsilon-near-zero modes to couple with plasmonic resonators. At sufficiently large laser pulse intensities, we predict the onset of optical bistability, while the presence of additional pump absorption resonances that arise from longitudinal oscillations of the free electron gas give way to corresponding resonances in the second and third harmonic spectra. A realistic propagation model is key to unraveling the basic physical mechanisms that play a fundamental role in the dynamics.

Tomasz Stefaniuk
Low-temperature fabrication of ITO films for nanophotonic applications
A. Korneluk, J. Szymczak, and T. Stefaniuk
Faculty of Physics, University of Warsaw, Poland
Indium tin oxide (ITO) is the most commonly used transparent conductive oxide in various types of electro-optical devices. To obtain simultaneously transparent and conductive layers, ITO is typically evaporated on substrates heated to high temperatures. Alternatively, the characteristics of deposited at room temperature ITO films can be improved by performing an additional annealing process. These approaches, however, are unsuitable in many types of nanoscale photonic systems as thermal treatment excludes the incorporation of polymers or metals into complex devices, with small features. Moreover, high temperature leads to the growth of large ITO crystallites, which size is often comparable with the dimensions of target nanostructures. In the presented study, we search for deposition conditions leading to the formation of ITO layers with an optimum combination of optical, electrical, and morphological properties in the low-temperature regime. We investigate the influence of oxygen, oxygen and argon plasma, deposition rate, and substrate temperature on the quality of ITO films, fabricated using e-beam evaporation. The key physical parameters of the samples were estimated based on atomic force microscopy images, scanning electron microscopy observations, hall measurements, and ellipsometry.
Keywords: indium tin oxide, thin films, e-beam evaporation.

Scott Watson
Distributed feedback lasers for quantum cooling applications
S. Watson¹, S. Gwyn¹, E. Di Gaetano¹, E. McBrearty¹, T. J. Slight², M. Knapp³, S. Stanczyk⁴, S. Grzanka⁴, A. Yadav⁵, K. E. Docherty⁶, E. Rafailov⁵, P. Perlin⁴, S. Najda⁴, M. Leszczynski⁴, M. Haji³, M. Sorel¹, D. J. Paul¹, and A. E. Kelly^1
1University of Glasgow, School of Engineering, Glasgow, UK
²Compound Semiconductor Technologies Global Ltd, Hamilton, UK
³National Physical Laboratory, Teddington, UK
⁴TopGaN Lasers, Warsaw, Poland
⁵Aston University, Birmingham, UK
⁶Kelvin Nanotechnology Ltd, Glasgow, UK
There is an ever-growing need for compact sources which can be used for the cooling process in high accuracy atomic clocks. Current systems make use of large, expensive lasers which are power-hungry and often require frequency doubling in order to hit the required wavelengths. Distributed feedback (DFB) lasers have been fabricated at a number of key wavelengths which would allow chip scale atomic devices with very high accuracy to become a reality. Two key atomic transitions analysed here are 88Sr+ and 87Rb which require cooling at 422 nm and 780.24 nm, respectively. The vital parameter of the DFB lasers for this application is the linewidth, as very narrow linewidths are required in order for the atomic cooling process to occur. The lasers realised here produce the required power levels, with high side-mode suppression ratios and show good single mode tuning which is important for hitting precise wavelengths. This work will present the latest techniques and results using the DFB lasers at both wavelengths.

Yi Yu
Dynamics of semiconductor Fano lasers
Yi Yu, T. S. Rasmussen, K. Yvind, E. Semenova, and J. Mørk
Technical University of Denmark, Lyngby, Denmark
Nanocavity devices enabling concentration of light in a very small volume have resulted in several interesting applications over the past years. In this talk I will present our recent investigations on the dynamics of a new type of semiconductor nanocavity laser, the Fano laser where one of the laser mirrors is realized by Fano interference effect between the continuum of waveguide modes and a side-coupled nanocavity, leading to a narrow-band mirror that provides the Fano laser with unique characteristics. In addition to being truly single-mode, the laser can be modulated through the mirror at frequencies far exceeding the relaxation oscillation resonance and the Fano mirror significantly alters the modulation response compared to Fabry-Perot lasers. The Fano laser concept is demonstrated using a photonic crystal platform with quantum dot active material. Both continuous wave operation and self-pulsing in gigahertz range are observed in optical pumping scheme at room temperature. We show that the self-pulsing is due to optical nonlinearities in the nanocavity that serves as a saturable mirror, leading to rich laser dynamics. In addition, we theoretically show that the Fano laser strongly suppresses dynamic instabilities induced by external optical feedback. A comparison with conventional Fabry-Perot lasers shows orders of magnitude improvement in feedback stability and in many cases even total suppression of coherence collapse, which is of major importance for applications in integrated photonics.

 

NetOrch invited presentations:

Josep Fabrega
Data plane elements for optical performance monitoring agnostic to the modulation format for disaggregated optical networks
J. M. Fabrega, F. Locatelli, L. Nadal, K. Christodoulopoulos, M. Svaluto Moreolo, and S. Spadaro
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Castelldefels (Barcelona), Spain
In this talk, data plane alternatives for optical performance monitoring are presented as enablers to address the key challenges in disaggregated optical networks. In fact, a key element of the disaggregated networks is the optical performance monitoring that is expected to deliver the feedback needed by the control plane to guarantee end-to-end quality of transmission and quality of service. Therefore, we will discuss data plane elements for non-intrusive monitoring agnostic to the modulation format, proposing and analyzing different schemes. Furthermore, we will also review the relevant figures of merit to be delivered to the SDN control, orchestration and management planes and their potential impact on the network performance.

Guido Maier
SD-WAN: An open-source implementation for enterprise networking services
S. Troia, L. M. Moreira Zorello, A. J. Maralit, and G. Maier
Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Italy
A reliable Wide Area Network (WAN) has become a necessity for businesses to transmit critical data between multiple branches and to increase their revenues. Software-Defined Wide Area Networking (SD-WAN) is an emerging paradigm that introduces the advantages of Software Defined Networking (SDN) into Enterprise Networking (EN). SD-WAN can support differentiated services over public WAN by dynamically changing the flow forwarding rules over an overlay network based on monitoring data and service requirements. This paper present an implementation of SD-WAN solution based on open source components, such as OpenDaylight as SDN controller, Open virtual Switch (OvS) and a set of services for network monitoring and policy based path selection. Our implementation provides a secured overlay WAN with high performance in terms of delay, losses and jitter over public WAN connectivity. We present an early implementation of this concept, describing a demo-test in a simple virtualised but realistic network environment, showing new features and advantages for the carrier in terms of resource optimization.
Keywords: SDN, Transport SDN, orchestration, automation, enterprise networking.

Quan Pham Van
Resource allocation for service fulfillment in multi-domain software-defined transport networks
H. T. Quang¹, Q. P. Van¹, T. H. Thieu¹, D. Verchere¹, and D. Zeghlache^2
1Nokia Bell Labs, Nozay, France
²Telecom SudParis, Evry, France
As optical networking managements are transforming, and optical systems are expanding everywhere, the demands for cross-domain and cross-layer transport network services are emerging, and consequently, operators need new functions enabling to automatically control their multi-domain optical infrastructure. With the recent advances of SDN technologies to Optical Transport Networks (L1-ODU) and Photonic-Media (L0-WDM), optical switching resources (e.g., ports, wavelengths, ODU, etc.) can be configured and monitored end-to-end to guarantee service requirements such as capacity and delays. In this paper, we first discuss the hierarchical multi-domain orchestration architecture for open disaggregated optical transport networks. Based on this architecture, we explain how end-to-end service fulfillment scheme for L1 connectivity services can be achieved by a path computation algorithm considering capacity and latency constraints and a port selection method for resource utilization. Finally, this design is experimented on the physical optical network to prove its operation.
Keywords; OTN/WDM, multi-domain service orchestration, open disaggregated optical transport networks, service fulfillment, L1 connectivity service.

Andrea Sgambelluri
Exploiting telemetry in multi-layer networks
A. Sgambelluri¹, F. Paolucci¹, A. Giorgetti¹, D. Scano¹, and F. Cugini^2
1Scuola Superiore Sant’Anna, Pisa, Italy
²CNIT, Pisa, Italy
Next generation networks are evolving towards multi-layer scenario, where packet and optical domains are coupled in different real networks. Regarding the optical domain, the white-box concept (i.e., the disaggregated network approach) is promising to break the vendor lock-in for the transmission solutions. While at the packet domain, since standard OpenFlow-based SDN techniques shown limited functionalities (i.e., missing stateful capabilities pipelining), novel P4-based solutions are emerging as candidate, envisaging the dynamicity of the traffic and the hardware programmability paradigm. In this scenario, the telemetry functionality is becoming an important solution for network monitoring, where data is efficiently streamed from network devices. In fact, in order to meet the service SLA requirements, next generation networks will leverage on advanced monitoring features, based on streaming techniques, allowing the control/management system to detect link failures and avoid traffic congestion. In this paper, we propose an experimental validation of a telemetry-based monitoring system in a multi-layer network. For the optical domain, we rely on an open-source implementation of an OpenConfig NETCONF agent enhanced with telemetry, in order to enable the streaming the value of key transmission parameters. For the packet layer, we exploit the P4 in-band telemetry, providing information on the end-to-end experienced latency and interfaces throughput. The monitoring system, enhanced with a proper GUI based on Grafana, is able to request the streaming of one or more selected parameter(s), on demand and with proper granularity, from different network domains. The implemented telemetry-based monitoring system has been experimentally validated over a multi-layer network encompassing EON and two P4 aggregation switches, highlighting the main functionalities and the effectiveness of the proposed solution.

 

NOA invited presentations:

Carmelo Bastos-Filho
Investigating the creation of a surrogate model for adaptive control of amplifier operating point using machine learning
C. J. A. Bastos-Filho¹, L. M. de Freitas², E. de A. Barboza², and J. F. Martins-Filho³
¹Polytechnic School of Pernambuco, University of Pernambuco, Recife, Brazil
²Computing Institute, Federal University of Alagoas, Maceió, Brazil
³Department of Electronics and Systems, Federal University of Pernambuco, Recife, Brazil
Dynamic operation is one of the current challenges in optical communication and networks, and the adaptive control of optical amplifier (ACOP) is one of the problems in this challenge. The ACOP approaches aim to define the gains of the optical amplifiers dynamically to increase the quality of the transmission after a cascade of amplifiers. The most recent ACOP approach uses a multiobjective evolutionary optimization algorithm to define the gains of the amplifiers to maximize the optical signal to noise ratio (OSNR) and to minimize OSNR ripple. Despite the promising results regarding Quality of Transmission, it is not desirable to rely on an evolutionary algorithm to make decisions in real-time. In this work, we investigate the creation of a surrogate model that can obtain solutions as good as the multiobjective algorithm, but in real-time. We show the results for a machine learning (ML) regression technique, trained with the optimization algorithm solutions, can return configurations with OSNR less than 1 dB close to the best OSNR returned by the optimization algorithm. Moreover, the ML solution answers in milliseconds, whereas the optimization-based approach needs several minutes to find a proper configuration.
Keywords: optical communication; optical amplifier; dynamic operation; adaptive control; machine learning.

Jonathan Bradley
Progress on ultra-compact on-chip rare-earth-doped amplifiers
J. Bradley, McMaster University, Hamilton, Canada

Vladimir Gordienko
Polarisation-insensitive fibre optic parametric amplifiers for applications in modern communication networks
V. Gordienko¹, F. Ferreira^1,2, C. Laperle³, M. O'Sullivan³, K. Roberts³, and N. Doran^1
1Aston Institute of Photonic Technologies, Aston University, Birmingham, UK
²now with University College London, UK
³Ciena Corporation, Ottawa, Canada
We evaluate and compare performance of three polarisation-insensitive fibre optic parametric amplifier (PI-FOPA) variants. We employ each variant to amplify a set of 21x50 GHz-spaced channels by 12.8±1.5 dB and analyse bit-error rate of an amplified 100G PDM-QPSK channel as power per channel is varied. We demonstrate two variants to provide a competitive noise figure of 6 dB. We envisage each of three PI-FOPA variants to be employed for broadband communications, phase-sensitive amplification and extended-reach PON respectively.
Keywords: fibre optic parametric amplification, polarisation, noise figure, nonlinear crosstalk.

Asif Iqbal
Ultra-wideband Raman amplifiers for high capacity fibre-optic transmission systems
M. A. Iqbal¹, L. Krzczanowicz², I. D. Phillips², P. Harper², A. Lord¹, and W. Forysiak^2
1British Telecom Laboratories, Ipswich, UK
²Aston University, Birmingham, UK
Raman amplifiers can provide gain over a very broad continuous spectrum to enable future ultra-wideband (UWB) transmission systems. We review different design choices of UWB (S+C+L-band) optical amplification technologies based on discrete and hybrid distributed-discrete Raman amplifiers and evaluate their performance in terms of overall noise figure, gain and effective bandwidth. We also review the design of an UWB optical source for amplifier characterisation, impacts of Raman pump linewidth, and nonlinear gain fibre properties on high capacity transmission performance.

Joseph Kahn
Impact and mitigation of polarization- or mode-dependent amplifier gain in ultra-long-haul systems
H. Srinivas, E. Chou, D. A. A. Mello, K. Choutagunta, and J. M. Kahn
E. L. Ginzton Laboratory, Department of Electrical Engineering, Stanford University, USA
We show by analysis and simulation of a multisection model that polarization- or mode-dependent gain from single-mode semiconductor optical amplifiers or multimode erbium-doped fiber amplifiers causes the channel capacity with minimum-mean-square error detection to become noticeably lower than that of optimal maximum likelihood detection. However, the capacity loss can be mitigated with techniques such as successive interference cancellation (SIC) that retain reasonable complexity. We reaffirm that frequency diversity enables the outage capacity to approach the average capacity and evaluate the performance of frequency-domain SIC equalizers for single-carrier transmission on frequency-selective optical fiber channels operating at 64 Gbaud up to 10,000 km.

Lukasz Krzczanowicz
High capacity wideband discrete Raman amplifiers: Progress, challenges, and future prospects
L. Krzczanowicz, M. A. Iqbal, I. D. Phillips, P. Harper, and W. Forysiak
Aston Institute of Photonic Technologies, Aston University, Birmingham, UK
Raman amplification is a popular method used to achieve seamless broadband gain. We evaluate the performance of discrete Raman amplifiers (DRAs) in high capacity C+L band transmission with advanced modulation formats and discuss the challenges associated with expanding the bandwidth to S+C+L band and beyond. Possible architectures, pump-signal overlap issues, and machine-learning based gain flattening techniques are considered.
Keywords: Raman scattering, optical fibre amplifiers, broadband amplifiers, optical fibre communications.

Karsten Rottwitt
Intermodal Raman scattering between orbital angular momentum modes in optical fibers
K. Rottwitt, N. M. Mathew, L. Grüner-Nielsen, and L. Rishøj
DTU Fotonik, Technical University of Denmark, Lyngby, Denmark
This paper presents an experimental and theoretical analysis of Raman amplification of OAM modes i.e. beams carrying orbital angular momentum and spin angular momentum. We show that simple scalar equations are sufficient to describe the Raman interaction between OAM modes when working in a cyclic basis. The equations are similar to those used when considering Raman amplification in conventional fibers used for optical communication. Such fibers are typically single mode and support propagation of LP modes i.e. light that is linearly polarized. In fibers that support propagation of OAM modes as well as in fibers that support propagation of LP modes the scalar equations apply when considering very short- fiber lengths or long fiber lengths, only the proper gain efficiency needs to be used. Here, we discuss the gain efficiency, its material and modal dependencies and we demonstrate that the Raman gain efficiency among OAM modes in comparison with the efficiency among LP modes mainly differs due to a typically larger mode size of OAM modes relative to that of the fundamental LP modes in conventional fibers used for optical communication. In addition, we demonstrate a mode dependent loss in an optical fibers that support propagation of OAM modes.
Keywords: nonlinear optics, fiber optics, optical amplifiers, OAM modes.

Leo Spiekman
Fiber-chip coupling of SOAs
L. H. Spiekman, Aeon Corp., Princeton Junction, NJ, USA
High performance semiconductor optical amplifiers require highly efficient fiber-to-chip coupling. In this paper. the difference with respect to fiber coupling to semiconductor lasers will be discussed, and the subject will be approached from a manufacturing perspective.

Feng Wen
Flat power response in a polarization-maintaining coupler based nonlinear-optical loop mirror (PMC-NOLM)
Feng Wen¹, Long Shao¹, Baojian Wu¹, Feng Yang², and Kun Qiu^1
1Key Lab of Optical Fiber Sensing and Communication Networks, Ministry of Education, University of Electronic Science and Technology of China, Chengdu, China
²Lab of Holographic Optical Sensing, Marolabs Co., Ltd, Chengdu, China
The nonlinear-optical loop mirror (NOLM) has been intensively investigated for the amplitude regeneration due to the power oscillatory mapping between the input and output waves. However, the noise-handling capability, i.e. the power plateau region is limited by the oscillatory nature, which becomes even worse when dealing with multiple levels. In the paper we review our novel NOLM regenerator scheme which is based on a polarization-maintaining coupler (PMC) instead of a conventional non-PM coupler (non-PMC). This modification brings the nonlinear polarization rotation effect into the NOLM unit, enabling significantly improving the regenerative range and the noise suppression efficiency. Compared to the conventional NOLM based on a non-PMC (non-PMC-NOLM), the proposed PMC-based NOLM (PMC-NOLM) offers an over 6dB flat power response, and consequently achieving 3.5dB Q-factor improvement in the regeneration experiment.
Keywords: nonlinear-optical loop mirror, amplitude regeneration, nonlinear polarization rotation.

 

Novel Glasses invited presentations:

Rolindes Balda
KLaF₄:Nd³⁺ emission in transparent glass-ceramics
R. Balda^1,2, S. Babu^3,4, A. A. Cabral⁵, M. Sedano⁴, D. Galusek⁶, A. Durán⁴, M. J. Pascual⁴, and J. Fernández^7
1Dept. Física Aplicada I, Escuela Superior de Ingeniería, Universidad del País Vasco (UPV-EHU), Bilbao, Spain
²Centro de Física de Materiales, (UPV/EHU-CSIC), San Sebastian Spain
³Dept. of Coating Processes, FunGlass, Alexander Dubček University of Trenčín, Trenčín, Slovakia
⁴Instituto de Cerámica y Vidrio (ICV-CSIC), , Madrid, Spain
⁵Departamento de Física, Instituto Federal do Maranhão – IFMA, São Luis, MA, Brazil
⁶Joint Glass Centre of the IIC SAS, TnUAD, and FChFT STU, FunGlass, Alexander Dubček University of Trenčín, Slovakia
⁷Donostia International Physics Center DIPC, San Sebastian, Spain
this work, transparent oxyfluoride glass-ceramics (GC) containing KLaF₄ nanocrystals obtained by Spark Plasma Sintering and doped with 0.1 and 0.5 (mol%) of NdF₃ are investigated. Site-selective laser spectroscopy in the ⁴I_9/2→⁴F_5/2 transition of Nd³⁺ performed in the GC samples confirms that Nd³⁺ is incorporated both in crystalline and amorphous phases. The differences among the spectral features of the site-selective excitation and emission spectra of Nd³⁺ in the studied glass and GC samples, allow to distinguish between crystalline and amorphous environments for Nd³⁺ ions and to correlate spectroscopic with structural properties.

Trevor Benson
Bright mid-infrared (MIR) photoluminescence sources and their application in imaging and sensing
D. Furniss¹, Boyu Xiao¹, A. B. Seddon¹, S. Sujecki¹, L. Sojka², Zhuoqi Tang¹, D. Jayasuriya¹, D. Mabwa¹, J. Nunes¹, R. Crane¹, S. Phang¹, E. Bereś-Pawlik¹, M. Farries¹, and T. Benson^1
1The University of Nottingham, UK
²Wroclaw Univ. of Science and Technology, Poland
Mid-infrared (MIR) spectroscopy and imaging underpins many applications, ranging from industrial production monitoring to environmental analysis, and offers a new era in healthcare and clinical diagnostics. A principal requirement for rapid measurement is bright, fibre-based, sources that ideally should also be robust and low cost. We will describe our work to develop such sources based on the photoluminescence from rare-earth doped chalcogenide glass fibres, and present some experimental results obtained in the fields of gas sensing and biomedical sensing and imaging.

Feifei Chen
Third-order optical nonlinearity of chalcogenide glasses within gallium-tin-selenium ternary system
Feifei Chen^1,2, Jiao Zhang^1,2, C. Cassagne³, and G. Boudebs^3
1Laboratory of Infrared Materials and Devices, The Research Institute of Advanced Technologies, Ningbo University, China
²Key Laboratory of Photoelectric Detection Materials and Devices of Zhejiang Province, Ningbo University, China
³Laboratoire de Photonique d'Angers, LPHIA, EA 4464, SFR MATRIX, University Angers, France
We explore the third-order optical nonlinear property of chalcogenide glasses (ChGs) within a gallium-tin-selenium (Ga-Sn-Se, GSS) ternary system at 1.064 μm in the picosecond regime. A classical characterization showing the values of the absorption and the linear index will be given. Then, using Z-scan D4σ technique, both nonlinear refractive index (n₂) and nonlinear absorption coefficient (β) of the GSS ChGs will be measured. A comparison of the results is made with other families of chalcogenide glasses considering the figure of merit calculation. The first results show that GSS system would give equivalent NL performance promising high potential for n2-based photonic devices.
Keywords: third order nonlinear measurement, Z-scan, chalcogenide glasses, Ga-Sn-Se.

Maurizio Ferrari
Glass photonics: Advancements and perspectives
A. Chiasera¹, A. Szczurek^2,1, K. Startek^3,4, O. Sayginer^5,1, L. T. N. Tran^1,6,7, M. Bollani⁷, S. Varas¹, A. Carpentiero¹, C. Armellini¹, A. Chiappini¹, L. Zur¹, W. Blanc⁸, B. Boulard⁹, P. Gluchowski⁴, D. Zonta^5,1,10, O. Bursi^5,1, J. Krzak², A. Lukowiak⁴, G. C. Righini^11,12, and M. Ferrari^1,11
1IFN-CNR CSMFO Lab. and FBK Photonics Unit, Trento, Italy
²Department of Mechanics, Materials Science and Engineering, Wroclaw University of Science and Technology, Poland
³Lukasiewicz Research Network - PORT Polish Center For Technology Development, Wroclaw, Poland
⁴Institute of Low Temperature and Structure Research, PAS, Wroclaw, Poland
⁵Department of Civil, Environmental and Mechanical Engineering, University of Trento, Italy
⁶Department of Materials Technology, Faculty of Applied Sciences, Ho Chi Minh City University of Technology and Education, Vietnam
⁷IFN-CNR, Milano, Italy
⁸Université Côte d'Azur, Institut de Physique de Nice, France
⁹IMMM UMR CNRS 6283, Université du Maine, Le Mans, France
¹⁰Department of Civil and Environmental Engineering, University of Strathclyde, Glasgow, UK
¹¹Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, Roma, Italy
Glass photonics is the cornerstone of a broad spectrum of human activities. Photonic glasses, planar light integrated circuits, functionalized waveguides, photonic crystals, thin films, coatings, microresonators, and microcavities are some examples of glass-based systems crucial in optical communication, sensing, biophotonics, processing, lightning, and quantum technologies. We present some recent results obtained by our consortium in rare earth doped photonic glasses and confined structures, in order to give some highlights regarding the state of art in glass photonics. Starting from planar waveguides glass ceramics we will move to fibers and photonic crystals. We will conclude the short review with some remarks about the exciting field of flexible photonics and the appealing perspective for glass-based photonic structures. The research activity is performed in the framework of the projects ERANet-LAC “RECOLA” (2017-2019), Centro Fermi “MiFo” (2017–2020), CNR-PAS “Flexible Photonics” (2020-2021), PRIN 2019 “NOMEN” (2020-2022).

Animesh Jha
RE³⁺-ion-doped and undoped 2D-MoS₂ thin films for optoelectronic and photonic device applications
J. R. Aswin¹, I. Arel¹, K. V. Adarsh², C. Maddi¹, A. J. Scott¹, and A. Jha^1
1School of Chemical and Process engineering, Faculty of Engineering, University of Leeds, UK
²Department of Physics, Indian Institute of Science Education and Research (IISER), Bhopal, India
Molybdenum disulphide occurs in nature and it is widely used for manufacturing high-temperature tribological films in the automotive sector. Its tribological attributes arising from 2D-layered structure places it alongside graphene for engineering novel application. More recently, the interest in the MoS₂ and other transition metal dichalcogenide (TMD) materials have grown for exploring optoelectronic and photonic properties, as these layered materials on sub-nanometre scale offer opportunities to explore quantum interactions [1]. The electronic structure and stoichiometry of TMDs make them distinguishable from the metallic graphene, as the TMDs depict a clear bandgap, as in compound semiconductors [2], which is quite attractive for device engineering and applications in photovoltaic, energy storage, and bandgap engineered light-sources [3]. In this talk, we will compare the structural properties of solution formed epitaxy like MoS₂ films with the naturally occurring crystalline MoS₂, CVD grown, and femto-second pulsed laser deposited (fs-PLD) undoped and rare-earth ion doped MoS₂. For fabricating nanometer scale PLD films of MoS₂, the source laser was a Ti-sapphire laser mode locked at 800 nm wavelength, with pulse duration of 100 fs and a repetition rate of 1 kHz. The deposition parameters for MoS₂ thin films, grown on silica substrate, was investigated by controlling and optimizing the process parameters, namely the laser fluence at 3 J/cm², argon (Ar) gas pressure inside the deposition chamber at 10 mTorr and substrate-to-target distance at 65 mm. The characterisation of different types of MoS₂ materials were carried out using the X-ray powder diffraction, Raman, FTIR, UV-visible spectroscopic, atomic force microscopic (AFM), transmission electron microscopy (TEM), electron energy loss spectroscopic (EELS), and X-ray photoelectron spectroscopic techniques, which enabled us to analyse the materials structure, electronic states and phonon vibration spectrum, essential for optoelectronic and photonic device engineering. For Yb³⁺-doped rare-earth doped thin films, we have also investigated the photoluminescence and nonlinear optical properties; the latter was characterised using the open aperture Z-scan technique. For Z-scan measurements, a 532 nm laser source (frequency doubled YAG) with 7 ns pulse duration and 10 Hz repetition rate was used to excite the MoS₂ films. In case of Yb³⁺ doped films, the enhancement in saturable absorption (SA) at room temperature was observed, the mechanism of which will be explained.
[1] F. Bonaccorso, Z. Sun, T. Hasan, and A. C. Ferrari, Nature Photonics 4, 611 (2010).
[2] S. Manzeli, D. Ovchinnikov, D. Pasquier, O. V. Yazyev, and A. Kis, Nat. Rev. Mater. 2 (8) (2017); Kin Fai Mak and Jie Shan, Nature Photonics 10, 216 (2016).
[3] O. V. Yazyev and A. Kis, Mater. Today 18 (1), 20 (2015); Haojie Zhang, N. Healy, A. F. J. Runge, Chung Che Huang, D. W. Hewak, and A. C. Peacock, Opt. Lett. 43 (13), 3100 (2018).

Petr Němec
Deposition of phase change materials via radio-frequency co-sputtering
M. Bouška¹, T. Halenkovič¹, V. Nazabal^1,2, J. Gutwirth¹, S. Normani¹, and P. Němec^1
1Department of Graphic Arts and Photophysics, Faculty of Chemical Technology, University of Pardubice, Czech Republic
²Institut des Sciences Chimiques de Rennes, UMR CNRS 6226, Université de Rennes 1, France
More than 50 years ago, reversible electrical switching phenomenon in amorphous chalcogenides was first time reported by Ovshinsky [1]. In the end of 1980s and beginning of 1990s, phase change materials based on Ge-Sb-Te and/or Ag-In-Sb-Te systems have been discovered. The main scientific as well as technological interest of these inorganic materials is their ability to transform quickly and reversibly between amorphous and crystalline phases. Fast phase transformation can be induced reversibly through varying the electric field or temperature by heating via a laser pulse in optical recording applications. The extraordinary properties of phase change materials based on Ge-Sb-Te ternary system are connected with changes of optical reflectivity (up to 30%) and/or electrical resistivity (several orders of magnitude) taking place upon phase transition [2]. Radio-frequency (RF) sputtering is widely used for thin films fabrication due to its relative simplicity, easy control, and often stoichiometric material transfer. Specifically, rf co-sputtering technique brings advantage of adjustable electrical power ratio applied on individual cathodes which enables to obtain thin films with various compositions making this method cost-effective for compositional dependencies’ studies of materials’ properties. Magnetron sputtering is widely used for the growth of chalcogenide phase change thin films. However, co-sputtering method is less frequent and mainly used for the doping of Ge-Sb-Te materials with other elements such as C, Al, Ti, Ni, Cu, Se, Zr, Sn or Bi. Contrary, RF co-sputtering is used in this work to explore fabrication of thin Ge-Sb-Te and Ga-Sb-Te films within broad region of chemical composition varying only the electrical power ratio applied to GeTe (or GaTe) and Sb₂Te₃ sputtering targets without necessity of exploiting many different compositions of the targets from Ge-Sb-Te or Ga-Sb-Te system when simple RF sputtering is employed. The characterization of thin films in as-deposited state (amorphous phase) as well as in crystalline state (induced by thermal annealing) was performed exploiting atomic force microscopy, scanning electron microscopy with energy-dispersive X-ray analysis, X-ray diffraction, electrical resistivity, and variable angle spectroscopic ellipsometry data. The results are discussed in relation with the chemical composition of the fabricated thin films. The financial support of the Czech Science Foundation under the project No. 18-03823S is greatly acknowledged.
[1] S. R. Ovshinsky, Phys. Rev. Lett. 21, 1450-1453 (1968).
[2] M. Bouska, S. Pechev, Q. Simon, R. Boidin, V. Nazabal, J. Gutwirth, E. Baudet, P. Nemec, Scientific Reports 6, 26552 (2016).

Laeticia Petit
Impact of Fe₂O₃ addition on the crystallization of Er³⁺ doped fluorophosphate glasses
I. Dmitrieva¹, W. Blanc², and L. Petit^1
1Photonics Laboratory, Physics, Tampere University, Finland
²Université Côte d'Azur, CNRS, Institut de Physique de Nice, France
Er³⁺ doped transparent oxyfluoride glass-ceramic (GC) materials have been of great interest as they have found applications in the telecommunications, optoelectronics, upconverting media, and near-infrared (NIR) or mid-infrared (MIR) emissions. If embedded in crystals with low phonon energies, the Er³⁺ ions can exhibit highly efficient visible upconversion and near infrared emission. The GCs are usually prepared by conventional melting followed by a thermal treatment. Transparency is obtained when the crystals precipitating in the glass are smaller in size than the wavelength of visible and infrared light and have similar refractive index than the glassy host. Recently, we showed that the glass composition in the system (75NaPO₃-(25-x)CaO-5CaF₂) (in mol%) had an impact on the diffusion mechanism of Er³⁺ ions during heat treatment [1]. The heat treatment of the glass with x = 25 led to transparent glass-ceramic with the precipitation of CaF₂ crystals doped with Er³⁺ ions. However, this glass had a poor glass stability preventing us to drawn it into fibers. In this presentation, we will discuss the impact of the addition of Fe₂O₃ on the crystallization mechanism of the glass with the composition 75NaPO₃-25CaF₂. We will first explain the preparation of the glasses and so the challenges related to the preparation of oxyfluoride glasses, which is sensitive to the melting temperature and crucibles. The effect of the glass composition on the spectroscopic properties and on the crystallization of the newly developed glasses will be reported. LP would like to acknowledge the financial support of the Academy of Finland (Flagship Programme, Photonics Research and Innovation (PREIN-320165) and Academy Project (308558)). WB would like to acknowledge the financial support of Institut Français in Helsinki, the French Ministry of Higher Education, Research and Innovation and the Finnish Society for Science and Letters (Programme Maupertuis).
[1] A. Nommeots-Nomm, N. G. Boetti, T. Salminen, J. Massera, M. Hokka, L. Petit, J. Alloys and Comp. 751 (2018) 224-230.

Laeticia Petit
Synthesis and properties of Er-doped KPO₃-Ca(PO₃)₂ glass and glass-ceramic
V. Lahti, A. Veber, and L. Petit
Photonics Laboratory, Physics, Tampere University, Finland
Phosphate glasses are of great technological interest due to specific thermal properties like low thermal glass transition and melting temperatures. In comparison to silicate glasses, rare-earth elements (REE) have higher solubility and REE-optical centers typically demonstrate higher absorption/emission cross sections in phosphate glasses. For these reasons REE-doped phosphate glasses have been used for many years as an active media for lasers and optical amplifiers. To the moment, it became clear that transparent glass ceramic materials have a great potential as a host medium for optical applications. Special attention is paid to the glass-ceramic (GC) materials, which allow to combine flexibility and scalability of the glass fabrication process with better thermal and optical properties of crystalline materials. In this context, fabrication of transparent REE-doped GCs starting from phosphate glasses should be the next step in the development of the active optical media for laser applications. However, despite significant progress in the development of oxyfluoride glass-ceramics, the phosphate based only GC materials are still rather rare. In the present work, we studied Er-doped KPO₃-Ca(PO₃)₂ metaphosphate glass and its devitrification behavior. Two concurrent crystallization processes (surface and bulk crystallization) are observed in this glass. The type of the process can be controlled by the temperature and duration during the nucleation and crystallization steps. At the same time two different phases of KCa(PO₃)₃ can be stabilized in the GCs: the hexagonal phase is mostly formed at the surface, whereas the orthorhombic isomorph determines the bulk crystallization. From the changes in the spectroscopic properties of the obtained GC materials, Er³⁺ ions are suspected to be incorporated in the lattice of the KCa(PO₃)₃, most probably entering the Ca²⁺ site. The optimization of the heat-treatment procedure allowed to prepare a transparent Er-doped phosphate glass-ceramic. Further steps to improve the crystallinity and quality of the GC will be discussed. The authors would like to acknowledge the financial support of the Academy of Finland (Flagship Programme, Photonics Research and Innovation (PREIN-320165) and Academy Project (308558)).

Diego Pugliese
High concentration Yb-Er co-doped multi-component phosphate glasses for compact eye-safe optical amplifiers
D. Pugliese¹, N. G. Boetti², D. Milanese³, and D. Janner^1
1Politecnico di Torino, Dipartimento di Scienza Applicata e Tecnologia (DISAT) and RU INSTM, Torino, Italy
²Fondazione LINKS – Leading Innovation and Knowledge for Society, Torino, Italy
³Università di Parma, Dipartimento di Ingegneria e Architettura (DIA) and RU INSTM, Parma, Italy
In recent years, the increasing need of airborne LIght Detection And Ranging (LIDAR) systems for environmental monitoring and surveillance has noticeably boosted the development of compact eye-safe optical amplifiers. In this scenario, multi-component phosphate glasses can be regarded as ideal candidate materials as they can be doped with a large amount of rare-earth (RE) ions without clustering, thus enabling the realization of few-cm long optical amplifier sections featured by high optical gain per unit length. In this work we will report the ongoing activities and the recent results obtained by our research group on the design, processing and characterization of a series of Yb-Er co-doped phosphate glasses to be used as active materials for the core of a waveguide amplifier. The physical, thermo-mechanical, optical and spectroscopic properties of the prepared glasses have been thoroughly investigated.
Keywords: phosphate glass, Erbium, Ytterbium, spectroscopic analysis, optical amplifier, LIDAR.

Vladimir Shiryaev
Chalcogenide glass fibers for analytical mid-IR spectroscopy of oil products and environmental objects
V. Shiryaev¹, E. Karaksina¹, T. Kotereva¹, A. Velmuzhov¹, B. Stepanov¹, and E. Boyko^2
1G.G. Devyatykh Institute of Chemistry of High-Purity Substances of the Russian Academy of Sciences, Nizhny Novgorod, Russia
²N. I. Lobachevski Nizhny Novgorod State University, Russia
In this paper, recent experimental results on the development of high-purity passive and active chalcogenide glasses and fibers for mid-IR fiber evanescent wave spectroscopy (FEWS) are presented. The high purity Ge-Se(-I), Ge-Sb-Se, Ge-As-Se-Te, and REE-doped Ga(In)-Ge-As(Sb)-Se glasses were prepared and studied. On the base of chalcogenide glass fibers, the sensor setup for studying the elemental composition of liquids by the method of evanescent spectroscopy was developed and created. To increase the sensitivity of FEWS sensors, novel types of chalcogenide fiber sensor probes were developed. Successful tests of different passive chalcogenide fibers as FEWS sensors and active doped fibers as luminescent middle infrared sources to determine the elemental composition of oil products and environmental objects were carried out.
Keywords: chalcogenide glasses, fibers, preparation, properties, mid-IR spectroscopy, oil products.

Manuel Vermillac
Micro- nano-structuring particles in optical fibers through the fiber drawing, experimental and numerical study
M. Vermillac¹, Z. Lu^2,3, H. Digonnet¹, F. Pigeonneau³, L. Rocha da Silva¹, W. Blanc^2
1Ecole Centrale de Nantes – Institut de Calcul Intensif (ICI), France
²Universite Côte d’Azur – Institut de Physique de Nice (INPHYNI), France
³MINES ParisTech – ParisTech – Centre de Mise en Forme des Materiaux (CEMEF), France
Particle-rich silica-based optical fibers are of great interest for the development of new optical devices. Indeed, nanoparticles may provide various properties, such as tailoring spectroscopic properties of luminescent ions or modifying light propagation in the media. In these regards, the optimisation of the beneficial effect of nanoparticles requires a control of composition, size, shape and spatial distribution of particles. To that aim, previous studies have highlighted the occurrence of shaping and structuring effects of the fiber drawing on particles. Following these observations, great interest is put in the control of these capillary effects during the fiber drawing to tailor the size, shape and spatial distributions of phase-separated particles. During the presentation, we will discuss the difficulties of assessing the shaping possibilities of the fiber drawing, and the ongoing numerical and experimental work that is done to overcome these issues.

Caroline Vigreux
Coupling waveguide-based probes and spectral multivariate analysis to detect liquids and biomolecules
B. Robert^1,2, A. T. Bendiad^1,2, R. Escalier¹, D. Heran², C. Vigreux¹, and R. Bendoula^2
1ICGM, Univ Montpellier, CNRS, ENSCM, Montpellier, France
²ITAP, INRAE, Montpellier SupAgro, Univ Montpellier, Montpellier, France
Rib optical waveguides based on Ge-Se-Te chalcogenide films were manufactured and their light transmission was studied as a response to the deposition of liquid droplets or biomolecules deposited on their surface. The transmission spectra at the output of the waveguides were recorded using a dedicated spectrophotometric bench working between 1200 and 2000 nm. As expected, liquid and biomolecules absorbed part of the evanescent wave of the guided light, leading to a decrease in the transmitted light. Principal Component Analysis and Partial Least Square as multivariate techniques then allowed the analysis of the statistics of the measurements and the predictive character of the transmission spectra. It confirmed the sensitivity of the probes based on chalcogenide rib waveguides to the liquid or biomolecule absorption, opening the door to their use for liquid spray characterization and bio-detection.
Keywords: chalcogenide rib waveguides, evanescent field, infrared spectrophotometry, liquid spray characterization and bio-detection.

 

OMT invited presentations:

Georges Boudebs
Mapping thermal effects in thin films using Z-scan based technique
O. Ba¹, M. Chis², C. Cassagne¹, and G. Boudebs^1
1Laboratoire de Photonique d'Angers, LPHIA, EA 4464, SFR MATRIX, Université Angers, France
²ESAIP, d'Anjou, France
The beam waist relative variation (BWRV) method known as a Z-scan based technique is used to demonstrate its feasibility in characterizing the thermal effects induced by a continuous laser beam of few mW in different materials. A study of several classical solvent-based solutions (water, ethanol, methanol ...) is carried out before introducing the extension of the BWRV method to laterally map the tested sample. We show that the transverse xy-scan of the sample allows to extract an image of the phase shift induced by local thermal heating. This new device, called XYZ-scan, is designed for the thermal characterization of inhomogeneous samples. An example will be given on an inhomogeneous 1 µm thin film doped with silver nanoparticles.
Keywords: thermal heating, phase shift, Z-scan, linear absorption.

Juan Bueno
Adaptive-optics polarization-sensitive second harmonic generation microscopy
J. M. Bueno¹, F. J. Ávila^1,2, R. M. Martínez-Ojeda¹, and P. Artal^1
1Laboratorio de Óptica, Universidad de Murcia, Spain
²Dept. Física Aplicada, Universidad de Zaragoza, Spain
An accurate visualization of structures containing collagen is essential for early detection and correct diagnosis of possible diseases. Second harmonic generation (SHG) microscopy is a non-invasive multiphoton technique allowing high-resolution imaging of collagen-based structures. However, this technique is limited by optical aberrations. Adaptive optics (AO) procedures are often used to compensate for optical aberrations and to improve multiphoton imaging. Moreover, since polarization modulates SHG signal, the acquired images show different features depending on the incident polarization state. In this work we demonstrate a multiphoton microscope combining AO and polarization-control for SHG imaging. Results show that polarization adds extra benefits to AO in terms of image quality enhancement. Although the performance depends on each particular sample and depth imaging location, results show up to a 3× improvement in SHG signal.

Eleonora Frau
Towards standards for light scattering studies of protein stability and nanoparticle-protein interactions
E. Frau and S. Schintke
Laboratory of Applied NanoSciences, Department of Industrial Technologies, HEIG-VD, HES-SO // University of Applied Sciences Western Switzerland (HES-SO), Yverdon-les-Bains, Switzerland
Protein-nanoparticle suspensions, are nowadays widely studied for the development of medical and environmental biosensors. The complexity of interactions between NPs and biological fluids, together with the increasing use of dynamic light scattering (DLS) for their characterization, support the need to develop common standards for DLS measurements and analysis, in order to enable a reliable comparison of measurement results, in particular for industrially oriented R&D. In this study, we use 3D cross-correlation Dynamic Light Scattering (3Dcc-DLS), an advanced recent DLS technique, that allows for the analysis of scattering intensities, diffusion coefficients, and hydrodynamic radii of particles (in a range between 1nm and 10 µm) even in samples of high concentration. The innovative configuration of 3Dcc-DLS suppresses directly during measurement any signal that would originate from multiple-scattering events. As model fluids, we use various suspensions of well-defined NPs (latex standard nano-spheres, Au nano-spheres and nano-rods of known dimension) and commercially available proteins, in order to develop suitable protocols for 3Dcc-DLS analysis. We perform tests at different concentrations and temperatures to determine the dependence of the particles’ properties in suspension, such as hydrodynamic radii, shape, type of interactions (attractive or repulsive), and denaturation or melting points. These data allow us to extract information on protein-protein and protein-NP interactions, as well as on their stability for different particle configurations under various controlled conditions. Our developed measurement and analysis protocols serve further application fields involving NPs and/or proteins, e.g. microfluidic biochips and complex bio-fluids, drug-delivery, or ink formulation and processing in printed electronics and bio-printing. This work has been financially supported by the HES-SO programme P3, project HENAPAMAT IA-EXT18-22-90667.

Ferruccio Pisanello
Depth-resolved optical monitoring of neural activity in freely moving animals
F. Pisano¹, M. Pisanello¹, S. J. Lee², J. Lee², E. Maglie^1,3, A. Balena^1,3, L. Sileo¹, B. Spagnolo¹, M. Bianco^1,3, M. Hyun², B. L. Sabatini² , M. De Vittorio^1,3, and F. Pisanello^1
1Istituto Italiano di Tecnologia, Center for Biomolecular Nanotechnologies, Arnesano, Italy
²Howard Hughes Medical Institute, Department of Neurobiology, Harvard Medical School, Boston, MA, USA
³Dip. di Ingegneria dell’Innovazione, Università del Salento, Lecce, Italy
Fiber photometry techniques are widely used to monitor the neural activity of genetically-targeted neural populations in behaving animals1–3. However, most implementations rely on flat-cleaved optical fibers, that can only interface with shallow tissue volumes adjacent to the fiber tip due to light scattering and absorption. We demonstrate that this important limitation can be circumvented by exploiting mode division using tapered optical fibers (TFs)4,5 to simultaneously collect photons at multiple depths6.We view our method as a promising technique in any biological system or organ in which light collection is beneficial but challenging because of light scattering and absorption.
[1] Adelsberger, H. et al. Nat. Neurosci. (2005).
[2] Adelsberger, H. et al. Cold Spring Harb. Protoc. (2014).
[3] Guo, Q. et al., Biomed. Opt. Express (2015).
[4] Pisanello, F. et al. Neuron (2014).
[5] Pisanello, F. et al. Nat. Neurosci. (2017).
[6] Pisano, F. et al., Nat. Methods (2019).

Luigi Sirleto
Adipocyte differentiation investigated by stimulated Raman microscopy based on femtosecond laser sources
M. A. Ferrara¹, A. Filograna², R. Ranjan¹, C. Valente², and L. Sirleto^1
1National Research Council (CNR), Institute for Microelectronics and Microsystems, Naples, Italy
²National Research Council (CNR), Institute of Protein Biochemistry, Naples, Italy
Lipid droplets (LDs) are dynamic organelles that play crucial roles in regulating the storage and the turnover of neutral lipids. Furthermore, extensive studies underline the relevant connection between lipid storage defects and the pathogenesis of several metabolic diseases, including obesity, diabetes, atherosclerosis as well as cancer. Nevertheless, many aspects of LD biology are still unrevealed, probably due to the current use of invasive imaging methods that often affect the formation and the maturation of LD. The current imaging techniques applied to study cellular lipid dynamic rely on fluorescence microscopy upon staining with neutral-lipid dyes, which are, however, only applicable to fixed samples and subject to variability depending on the experimental conditions. Unfortunately, these fluorescent dyes are often nonspecific and interfere with the lipid-mediated biological processes introducing imaging artifacts in cell recordings (e.g., may cause changes in LDs fusion behaviour) Thus, it becomes increasingly urgent to develop reliable imaging tools to unambiguously examine the dynamics of LD accumulation within their cellular context. Here, we used Stimulated Raman Scattering (SRS) microscopy as a label-free method to image LDs in 3T3-L1 adipocyte cells. This non-invasive technique allows us to acquire images with high spectral and spatial resolution along with three-dimensional sectioning and resolving capabilities of lipids and proteins during adipocyte differentiation. Our results show an increased number of large (> 15 μm2) LDs during adipocyte differentiation. Furthermore, we provide a detailed separation of cellular distribution and spatially resolved maps of lipids and proteins at different stages of adipocyte differentiation. Our data demonstrate that stimulated Raman imaging is an advanced label free approach that allows to examine the physiology of intracellular lipids and opens up new avenues for the diagnosis of LD-associated pathologies.
[1] Ferrara MA, Filograna A, Ranjan R, Corda D, Valente C, Sirleto L (2019) Three-dimensional label- free imaging throughout adipocyte differentiation by stimulated Raman microscopy, PLoS ONE 14(5): e0216811.
[2] R. Ranjan, M. A. Ferrara, A. Filograna, C. Valente and L. Sirleto, Femtosecond stimulated Raman microscopy: Home-built realization and a case study of biological imaging, Journal of Instrumentation, (2019), vol. 14, P09008.
[3] Ranjan, R., Indolfi, M., Ferrara, M. A., Sirleto, L. Implementation of a nonlinear microscope based on stimulated Raman scattering, J. Vis. Exp. (149), e59614, doi:10.3791/59614 (2019).
[4] R. Ranjan, A. D’arco, M. A. Ferrara, M. Indolfi, M. Larobina, L. Sirleto, Integration of stimulated Raman gain and stimulated Raman losses detection modes in a single nonlinear microscope, Optics Express, Vol. 26, Issue 20, pp. 26317-26326, (2018).

 

OptSoft invited presentations:

Hamzeh Khalili
Study on softwarization of management wavelength allocation in EPON networks
H. Khalili, P. S. Khodashenas, and M. S. Siddiqui
i2CAT Foundation, Barcelona, Spain
Wavelength Division Multiplexing Passive Optical Network (WDM-PON) being developed to carry multiple services in PON network. WDM has a high cost of initial set up and maintenance of the components, as well as power consuming. Considering end-user requirements (i.e. multi services, high bandwidth and performance), it is extremely essential to provide a framework to manage multi-wavelengths in PON networks. Software defined Networking (SDN) and Network Function Virtualization (NFV) paradigms are potential solutions, paving the way for efficient management and operation, enabling softwarization, virtualization and centralization of distributed functions. In this work, we proposed an SDN-based AI solution for managing the wavelength based on user requirements and daily internet usage patterns. For this, a monitoring module is used for telemetry and event collector. To make the best decision, all daily collected data will be sent to the AI layer.
Keywords: EPON, SDN, NFV, artificial intelligence, passive optical network, machine learning.

Noemi Merayo
An experimental SDN proposal over legacy GPONs to allow real-time service and residential network reconfiguration
N. Merayo, D. de Pintos, J. C. Aguado, R. J. Durán, I. de Miguel, P. Fernández, R. M. Lorenzo, and E. J. Abril
Optical Communications Group, Department of Signal Theory, Communications and Telematic Engineering, E.T.S.I. Telecomunicación, Universidad de Valladolid, Spain
In this paper we propose an experimental SDN solution over legacy GPON equipment that allows to control the network configuration and its services. The proposal permits a central SDN controller to take over from GPON the management of certain global bandwidth and service configuration policies. In legacy PONs the real-time bandwidth allocation process is carried out inside the network infrastructure cycle by cycle between the OLT (Optical Line Terminal) and the ONTs (Optical Network Terminals), which can adversely affect the network performance in scenarios that include change of policies due to the latency between the SDN controller and the PON. In contrast, the control of some global DBA strategies by SDN techniques could lead to better network and management configuration and therefore our proposal is able to dynamically adjust these policies according to the real-time Quality of Service (QoS) requirements of residential users. On the other hand, the designed SDN proposal permits network subscribers to control the performance of their residential homes. In this way, they can set constraints and dynamically customize the bandwidth of their connected devices in a very transparent and efficient way.

David Rincon Rivera
Leveraging SDN-based management for improved traffic scheduling in PONs
M. Zehri^1,2, A. Haastrup¹, D. Rincón¹, J. R. Piney¹, S. Sallent¹, and A. Bazzi^2
1Dept. of Network Engineering, Universitat Politècnica de Catalunya, Barcelona, Spain
²School of Engineering, Lebanese International University, Lebanon
Building on top of an Software-Defined Networking (SDN)-based management architecture developed in previous works, we add advanced traffic scheduling, QoS and energy saving features to Time- and Wavelength Division Passive Optical Networks (TWDPONs). We are able to manage some parameters of the Dynamic Bandwidth Algorithm (DBA), including the scheduling policy and weight-based QoS differentiation of users, taking into account the laser tuning time, an important and realistic constraint in multiwavelength PONs that is usually neglected.

Josep Segarra
Practical design of a coherent ultra-dense WDM-PON with paired DFB lasers
J. Segarra, V. Sales, V. Polo, and J. Prat
Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
A coherent WDM-PON achieving ultra-dense spectral allocation is reported. The ONU at user premises is built of coherent transceivers with two low cost paired DFB lasers, one as local oscillator and the other as transmitter, offering simplicity and low cost hardware. The DFB lasers at the ONU are paired to realize a simple blind activation process, having wavelengths with limited thermal tunability controlled by thermo-electric coolers for the wavelength allocation. A MAC at the OLT at central office manages the spectrum channel assignment for ONUs demanding connection with random wavelength: the OLT furnishes an optical carrier wavelength for the new active ONU by a smart control algorithm, thus assigning a down-channel; subsequently, another paired up-channel is also allocated to the ONU laser transmitter. The MAC can reassign the channels because of interference, collision or any network needs in a Dynamic Wavelength Allocation (DWA), which can be integrated in a SDN function. The channelization of the optical bandwidth is flexible, thus adapting to different user bandwidths, serving all sort of bit rates and suited for 5G technologies. Measures in an activation process and in channel reassignment have been performed in environment conditions, demonstrating the feasibility of the system.

 

OSCto5G invited presentations:

Ivan Djordjevic
Security of satellite-based CV-QKD under realistic assumptions
Ziwen Pan, and I. B. Djordjevic
The University of Arizona, Tucson, USA
With the vastly growing need for secure communication, quantum key distribution (QKD) has been developed to provide high security for communications against potential attacks from the fast-developing quantum computers. Among different QKD protocols, continuous variable (CV-) QKD employing Gaussian modulated coherent states has been promising for its complete security proof and its compatibility with current communication systems in implementation with homodyne or heterodyne detection. Since satellite communication has been more and more important in developing global communication networks, there have been concerns about the security in satellite communication and how we should evaluate the security of CV-QKD in such scenarios. To better analyse the secure key rate (SKR) in this case, in this invited paper we investigate the CV-QKD SKR lower bounds under realistic assumptions over a satellite-to-satellite channel. We also investigate the eavesdropper's best strategy to apply in these scenarios. We demonstrate that for these channel conditions with well-chosen carrier centre frequency and receiver aperture size, based on channel parameters, we can optimize SKR correspondingly. The proposed satellite-based QKD system provides high security level for the coming 5G and beyond networks, the Internet of things, self-driving cars, and other fast-developing applications.
Keywords: quantum key distribution, satellite-based communication

Alexis Dowhuszko
LEO satellite constellations to offload optical terrestrial networks in placement of popular content in 5G edge nodes
A. Dowhuszko¹, J. Fraire², M. Shaat¹, and A. Pérez-Neira^1
1Centre Tecnològic de Comunicacions de Catalunya (CTTC), Barcelona, Spain
²Universidad Nacional de Córdoba (UNC), Córdoba, Argentina
With the proliferation of new data-consuming applications, such as on- demand video streaming services like YouTube and Netflix, telecom operators have been forced to find solutions to deal with the much higher data demand of customers that are not willing to pay much more for their subscription fee. One of these options has been the construction of Content Delivery Networks (CDN) owned by the operators, where the most popular content to-be-requested by the subscribers is predicted on a daily basis, and cached in advance in the 5G edge nodes associated to the subscribers during the off-peak hours. For this purpose, point-to-point wired (optical fibre) or wireless (Free-Space Optical) links are conventionally used to connect the operators’ servers with the 5G edge nodes. However, due to the multi-hop physical topology that terrestrial backhaul links have, the same content must be transmitted in parallel to each of the edge nodes that requests it, reducing notably the throughput of the end-to-end connections that are established even when the data rate that individual optical links can support is high. One simple way to tackle this problem consists in offloading the terrestrial optical backhaul network during cache filling by broadcasting over satellite the most popular content to the edge nodes that share the same spot beam. The benefits of using GEO satellites to minimize the cache filling time of a 5G edge network with optical wireless links has been studied in [1]. In this paper, the use of a constellation of LEO satellites will be considered instead, taking into account the advantages and challenges imposed by low-orbits dynamics, which can be summarized as closer communication ranges but with sporadic contacts with ground points of interest. This approach is aligned with the current launch schedule of more than 17000 LEO satellites spanning the so-called “new space” mega-constellations, which could use their spare storage resources to speed up the delivery of most popular content to 5G edge nodes.
[1] A. Dowhuszko, M. Shaat and A. Pérez-Neira, “Integration of optical and satellite communication technologies to improve the cache filling time in future 5G edge networks,” in Proc. 21st International Conference on Transparent Optical Networks, July 2019, pp. 1-5.

Ramón Durán
Comparison of different protection schemes in the design of VNF-mapping with VNF resiliency
L. Ruiz, R. J. Durán, I. de Miguel, N. Merayo, J. C. Aguado, P. Fernández, R. M. Lorenzo, and E. J. Abril
Optical Communications Group, Universidad de Valladolid, Spain
NFV is a promising networking paradigm which is expected to ease the manageability of networks, increase its flexibility, reduce costs and be one of the enabling technologies of 5G. In this kind of networks, operators must solve the Virtual Network Function (VNF) placement and chaining. Furthermore, it is important to provide backup resources to ensure the survivability of the offered network service when a node failure happens. In this paper, we compare two different protection approaches to ensure the Service Chain resiliency: individual VNF protection and end-to-end, node disjoint, SC protection. Results show the benefits in terms of computing resources and energy consumption of protecting each VNF individually, compared to the end-to-end protection approach.
Keywords: VNF-placement, VNF-chaining, VNF-protection, end-to-end protection, individual VNF protection, node failure, 5G, NFV, resilience.

Hamzeh Khalili
On the orchestration of integrated satellite components in 5G networks and beyond
H. Khalili, P. S. Khodashenas, and S. Siddiqui
i2CAT Foundation, Barcelona, Spain
In support of inclusion of non-terrestrial network, 3GPP standardization recently developed several technical reports and specifications on the possible role of satellite systems along with the terrestrial network communications. The newest 3GPP study items under 5G created opportunity to integrate satellite systems, even beyond 5G networks. Integration between these two technologies will bring new range of features such as universal multi-access, dynamic management and ubiquitous connectivity, as well as increasing coverage, availability and reliability. This can be achieved through virtualization of satellite ground segment components, APIs and orchestration platform. In this work, we proposed an orchestration solution to manage and coordinate inter and intra satellite communication (i.e. GEO, MEO, LEO), together with terrestrial network resources. The solution is highly flexible and allows easy configuring of satellite systems including, baseband user segment, network user segment and mission segment in order to respond adequately to service requirements and end-to-end service provisioning.
Keywords: 5G network, network function virtualization (VFV), integrated satellite terrestrial networks, coordination layer, management and orchestration.

Aris Lalos
5G enabled cooperative localization of connected and semi-autonomous vehicles via sparse Laplacian processing
N. Piperigkos^2,3, A. S. Lalos^1,3, K. Berberidis², C. Laoudias⁴, and K. Moustakas^3
1Industrial Systems Institute, Athena Research and Innovation Center in Information Communication and Knowledge Technologies, Patra, Achaia, Greece
²Computer Engineering and Informatics Department, University of Patras, Greece
³Dept. of Electrical and Computer Engineering, University of Patras, Greece
⁴KIOS Center of Excellence, University of Cyprus
Cooperative Localization has received extensive interest from several scientific communities including robotics, optimization, signal processing and wireless communication. It is expected to become a major aspect for a number of crucial applications in the field of connected and (semi-)autonomous vehicles, such as collision avoidance/warning, cooperative adaptive cruise control, safely navigation, etc. 5G mobile networks will be the key to providing connectivity for vehicle to vehicle (V2V) and vehicle to infrastructure (V2I) communications, allowing Connected and (Semi-)Autonomous Vehicles (CAV) to share with other entities of the network the data they collect and measure, robustifying cooperative network localization. Typical measurement models usually deployed for this problem, are absolute position information from Global Positioning Systems (GPSs), relative distance to neighboring vehicles and relative azimuth angle or angle of arrival, from Light Detection and Ranging (LIDAR) or Radio Detection and Ranging (RADAR) sensors. In this paper, we provide a cooperative estimation approach that performs multi modal fusioning between the interconnected vehicles. This method is based on the so called Laplacian graph Processing, that is a well-known Graph Signal Processing tool, significantly outperforming current state of the art approaches in various mobility scenarios, assuming different network topologies and motion patterns.

Christos Laoudias
GNSS location verification in connected and autonomous vehicles using in-vehicle multimodal sensor data fusion
N. Souli^1,2, C. Laoudias¹, P. Kolios¹, C. Vitale¹, G. Ellinas^1,2, A. Lalos^3,4, J. Casademont^5,6, P. S. Khodashenas⁶, and P. Kapsalas^7
1KIOS Research Center, University of Cyprus, Nicosia, Cyprus
²Department of Electrical and Computer Engineering, University of Cyprus, Nicosia, Cyprus
³Electrical and Computer Engineering Department, University of Patras, Rio, Patras, Greece
⁴Industrial Systems Institute, “ATHENA” Research Centre, Patras, Greece
⁵Wireless Networks Group, Universitat Politecnica de Catalunya (UPC), Barcelona, Spain
⁶Software Networks Area, i2CAT Foundation, Barcelona, Spain
⁷Panasonic Automotive Systems Europe, Frankfurt, Germany
Connected and Autonomous Vehicles (CAVs) rely on Global Navigation Satellite Systems (GNSS), e.g., the Global Positioning System (GPS), for the provision of accurate location information for various functionalities including Vehicle-to-Vehicle/Infrastructure (V2V/V2I) communication and self-navigation. However, GNSS-based location awareness is prone to spoofing attacks, where the attacker generates counterfeit satellite signals. This in turn poses a serious threat to the CAV, e.g., car, drone, etc., as well as the surrounding entities. Thus, this threat needs to be detected reliably and mitigated timely to prevent undesired consequences (e.g., damages, casualties, etc.). To this end, this work proposes a location verification solution that leverages in-vehicle sensor readings (e.g., accelerometer, etc.) and Signals of Opportunity (SoO), as an alternative source of location information. In particular, the multimodal sensor data with SoO location measurements are fused by means of a Kalman filter and the estimated fusion-based location is used to verify the location output of the GPS receiver. In case the GPS location deviates considerably from the fusion-based location, then a location spoofing attack is ascertained. Preliminary experimental results with real GPS and sensor data collected with a drone demonstrate the effectiveness of the proposed approach.
Keywords: connected and autonomous vehicle, location spoofing, signals of opportunity, data fusion.

Harri Saarnisaari
5G new radio in SatCom: An overview of physical and medium access layer issues
H. Saarnisaari and C. Morais de Lima
University of Oulu, Finland
We will provide an overview what are the challenges at PHY and MAC layers in 5G new radio (NR) if it is applied to SatCom. Work done in 3GPP as well as in literature and projects will be evaluated. Furthermore, recent results related to efficient use of high power amplifiers with NR are shown.

 

OWW invited presentations:

Jian Chen
Anti-shadowing design of visible light communication and positioning systems with equivalent virtual lamps
Jian Chen, Wenqian Sun, Lingfang Ma, and Renzhou Wang
School of Telecommunications and Information Engineering, Nanjing University of Posts and Telecommunications, China
the visible light transmission link between a detector and the lamps, the transmitted signal is rebuilt via different line-of-sight (LOS) and non-line-of-sight (NLOS) propagation with LOS generally dominant. Under a visible light communication (VLC) scenario, there is the requirement to ensure the flatness of both illumination and signal-to-noise ratio across the whole receiving plane. In the case of visible light positioning (VLP) scenario, the basic requirement is to keep as many lamps to have LOS links with the receiver across the positioning plane. However, the design of both VLC and VLP systems are strictly limited by a sophisticated combination of the parameters of the detector and the lamps. In a real application, it may deviate from the desired working condition which results in performance deterioration of a VLC system or even failure of a VLP system. We proposed a mirror-assisted scheme to alleviate such problems, which is based on the assumption of equivalent virtual lamps. With the integrated design and characterization by considering both the existing and virtual lamps, it can be expected to enhance the anti-shadowing functionality of both VLC and VLP systems with flexibility.

Ernesto Ciaramella
Prospects of visible light communications in satellites
E. Ciaramella¹, G. Cossu¹, E. Ertunc¹, L. Gilli¹, A. Messa¹, M. Presi¹, M. Rannello¹, F. Bresciani², V. Basso², R. Dell’Orso³, and F. Palla^3
1Scuola Superiore Sant’Anna, Pisa, Italy
²Thales Alenia Space, Torino, Italy
³Istituto Nazionale di Fisica Nucleare, Pisa, Italy
We present the exploratory approach of Project FOCS (Free Space Optical communications for Space), which aims at proposing and demonstrating new applications of Visible Light Communications (VLC) for satellites. The first selected application scenario that will be investigated deals with low-bit-rate communication between satellites over >100 m distances. The second selected research line will be about transmission of Gbit/s signals on very small satellites, e.g. CubeSats.

Giulio Cossu
Can we replace an on-board communication bus in large satellites by means of optical wireless signals?
E. Ciaramella¹, G. Cossu¹, E. Ertunc¹, L. Gilli¹, A. Messa¹, M. Rannello¹, F. Bresciani², J. Girella², E. Pifferi³, and V. Podda^3
1Scuola Superiore Sant’Anna, Pisa, Italy
²Thales Alenia Space, Torino, Italy
³Thales Alenia Space, Roma, Italy
We present the requirements for replacing a MIL-STD-1553 communication bus by optical links in a telecom satellite. We then introduce the typical operating conditions and present the results of numerical modelling in the most relevant cases under study.

Taisir El-Gorashi
Resource allocation in co-existing optical wireless HetNets
O. Z. Alsulami¹, S. O. M. Saeed¹, S. H. Mohamed¹, T. E. H. El-Gorashi¹, M. T. Alresheedi², and J. M. H. Elmirghani^1
1School of Electronic and Electrical Engineering, University of Leeds, UK
²Department of Electrical Engineering, King Saud University, Riyadh, Kingdom of Saudi Arabia
Optical wireless communication (OWC) systems are a promising communication technology that can offer very high data rates beyond 10 Gbps and into the Tbps regime and can support multiple users at the same time. However, Interference between users and cells can significantly affect the quality of OWC links. Thus, in this paper, a mixed-integer linear programming (MILP) model is developed to establish the optimum resources allocation in wavelength division multiple access (WDMA) optical wireless systems. Consideration is given to the optimum allocation of wavelengths and access points (APs) to each user to support multiple users in an environment where Micro, Pico and Atto Cells co-exist for downlink communication. The high directionality of light rays in small cells such as Pico and Atto cells can offer a very high signal to noise and interference ratio (SINR) at high data rates. Consideration is given in this work to visible light links which utilize four wavelengths per access point (red, green, yellow and blue) for Pico and Atto cells systems, while the Micro cell system uses an infrared (IR) transmitter.

Ronald Freund
Demonstration of optical wireless communications using the pulsed modulation PHY in IEEE 802.15.13
M. Hinrichs^1,2, C. Schmidt¹, B. Poddig¹, J. Hilt¹, P. Hellwig¹, D. Schulz¹, K. L. Bober¹, J. Schostak¹, R. Freund^1,2, and V. Jungnickel^1,2
1Fraunhofer Heinrich Hertz Institute, Berlin, Germany
²Technische Universität Berlin, Institute of Telecommunication Systems, Berlin, Germany
In optical wireless communications (OWC), orthogonal frequency division multiplexing has become a common choice of modulation as it is well established in both wired and radio frequency wireless applications. While it has advantages such as high spectral efficiency and robustness against multi-path propagation, power efficiency is suboptimal when using it together with intensity modulation and direct detection over optical channels. Unlike in the radio frequency domain, availability of spectrum is not a limiting factor, so range can be improved by using a wider bandwidth, lower spectral efficiency and, accordingly, simpler modulation techniques. In this paper, we experimentally demonstrate the performance of a complete physical layer based on on-off-keying and frequency-domain equalization as it is specified in IEEE 802.15.13 and prove its applicability to OWC.
Keywords: optical wireless communications, on-off-keying, physical layer development.

Véronique Georlette
Visible light communication challenges in the frame of smart cities
V. Georlette¹, V. Moeyaert¹, S. Bette^1,2, and N. Point^3
1Electromagnetism and Telecommunications Dept., University of Mons, Belgium
²Management of Innovation Technology Dept., University of Mons, Belgium
³Network Engineering Dept., Multitel, Belgium
Visible Light Communication (VLC) is the family of telecommunication technologies that uses the visible range of the electromagnetic spectrum to send data. The main asset of this emerging technology is that a light can simultaneously illuminate and communicate. This technology is for now, only possible by using Light Emitting Diodes (LEDs) and can reach up to hundreds of Mbit/s bidirectional. Furthermore, thanks to the adoption of LED lighting by cities and for car lights, VLC is about to bring a lot of interconnectivity possibilities among devices in the city, making this latter smarter. Even though outdoor VLC is still in the research phase, the main promising applications foreseen by this technology are urban Li-Fi (Light Fidelity) to complement the Wi-Fi offer, VLC-IoT (Internet of Things) and V2X (Vehicle to Vehicle or Vehicle to Infrastructure). VLC-IoT is envisioned as a streetlight communicating with the surrounding urban furniture or a streetlight sending location-based content to a visitor located under its light beam. V2X is intended to communicate with each other and/or with the street infrastructure. In this way, VLC could reply to the lack of connectivity in some places and relieve the RF spectrum when it gets crowded. This work outlines and surveys the current state of Visible Light Communication in outdoor environments, its main challenges (mainly due to weather variability), the most promising outdoor applications and the still ongoing standardisation efforts in the context of Smart Cities.

Jian-Jang Huang
Toward Gbps data rate transmission using nitride based LEDs with modified radiation modes
Jian-Jang Huang, Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan
Visible light communication (VLC) is an alternative form of wireless communication using modulated light in the visible spectrum as the transmitter. VLC offers the advantages of low cost, unregulated bandwidth and ubiquitous infrastructures support, making it one of the ideal solutions for the demand of data transmission bandwidth. In this work, using GaN-based LEDs with embedded PhCs, we demonstrated a higher small-signal E-O conversion frequency than the device without PhCs. The guided photonic modes of the LEDs are modulated by the RF signal. Both carrier lifetime of lower- and higher-order modes are studied in time-resolved photoluminescence (TRPL) at room temperature. The f_-3dB-J curve of the PhC LED exhibits a higher bandwidth than the typical LED structure. At 11.41 kA/cm², the optical -3-dB bandwidth (f_-3dB) up to 234 MHz of the PhC LED (PhCLED) is achieved. Next, we studied large-signal responses of the devices. Contradictory to general thought that higher small-frequency response translates to better large-signal performance, our results reveal that a PhC LED may not perform well at low data rate due to its relatively poorer signal-to-noise ratio (SNR). However, at higher data rates, the performance of PhC LEDs surpasses conventional LED structure. We showed data transmission capability of PhC LEDs with a bit rate up to 400 Mb/s using on-off keying (OOK) modulation. To demonstrate the chip capability for large-signal transmission, without using pre- or post- emphasis, VLC with 16-quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) transmission capacity up to 2 Gbit/s is achieved with an error vector magnitude (EVM) of 17.0%, signal-to-noise ratio (SNR) of 15.35 dB and bit-error-rate (BER) of 3.3×10^-3. Our LEDs embedded with PhCs pass the forward error correction (FEC) criterion. The results reveal the advantages of LEDs with PhC for achieving higher data rate transmission.

Volker Jungnickel
A flexible system concept for LiFi in the Internet of Things
K. L. Bober¹, V. Jungnickel¹, M. Emmelmann², M. Riegel³, E. Tangdiongga⁴, A.M.J. Koonen⁴, J.-P. Linnartz^4,5, D. Behnke⁶, M. Müller⁶, P.-B. Bök⁶, S. V. Colonques⁷, and M. M. Vazquez^7
1Fraunhofer HHI, Germany
²Fraunhofer FOKUS, Germany
³Nokia Bell Labs, Germany
⁴TU Eindhoven, Netherlands
⁵Signify, Netherlands
⁶Weidmüller, Germany
⁷MaxLinear, Spain
The evolving Internet of Things (IoT) opens a new mass market for wireless communications. Future IoT applications have diverse performance requirements, such as high data rates, reliable time-sensitive networking, support for high mobility and high user density. As a potential key role in the sixth generation (6G) mobile communication networks, light fidelity (LiFi) exploits light waves to transmit data. In this paper, we propose a flexible system concept for LiFi, addressing the heterogeneous demands of future IoT applications, while using harmonized technology. We identify the technical core components and show how to integrate them into specialized solutions for each application. We exemplify four use cases for LiFi: a) in-home b) enterprise, c) industrial wireless networks, and d) fixed wireless access outdoor links.
Keywords: LiFi, IoT, system concept.

Thomas Kamalakis
PyVisComm: A Python module for simulating visible light communication systems
F. Simou, L. Dogkas, and T. Kamalakis
Department of Informatics and Telematics, Harokopio University of Athens, Greece
Visible light communication (VLC) is an emerging technology in the telecommunications sector that is taking a step beyond conventional radio frequency communication. It is a communication technology in which the visible spectrum is configured for data transmission and has a short range. VLC relies on the reuse of the illumination of light emitting diodes (LEDs) for communication purposes as well. Due to the complex nature of the optical transmitter and channel, we need an efficient tool for simulating, designing and optimizing the VLC system configuration. In this work, we present the Python PyVisComm module, which is publicly available and can be used for simulating a VLC system using discrete multitone modulation (DMT) taking into account the transceiver arrangement, the ambient light noise sources, the modulation parameters (subcarrier number, modulation order, clipping ratio) and several other key aspects of the system. We discuss various implementation strategies and illustrate how PyVisComm can be used to determine the system’s performance under various metrics including the bit error and the signal-to-noise ratios. We also discuss how the transmitter can be realistically modeled taking into account the LED frequency response and non-linearity.

Daniel King
An evolution of optical network control: From Earth to space
D. King¹, A. Farrel², and Zhe Chen^3
1Lancaster University, UK
²Old Dog Consulting, UK
³Huawei, UK
The recent evolution from Wavelength Diversion Multiplexing to flexible or Elastic Optical Networks (EON), and the new transport infrastructure they can support, required the development of new innovative optical control systems. We are now seeing the need to integrate these flexible Earth-based optical networks with space-based Low, Medium, and High Earth Orbit (LEO, MEO and HEO) satellite clusters, using Free-Space Optical (FSO) Communication. Current and near-future space-based networks include Telesat with 120 satellites and 40 grounds stations, OneWeb with 720 satellites and 70 ground stations, and SpaceX with planned 42,000 satellites and 120 ground stations. Also, several additional Satellite Internet projects are proposed for operational deployment by 2025. Total throughput using these space satellite networks ranges from 3 Tbps per cluster to more than 50 Tbps. These new networks provide connections of 100s Mbps to Residential users and Gbps to Enterprise users. Control and communication across fixed and free-space optical networks present several problems – high dynamicity, spatial connectivity, continual movement tracking and prediction, ocular obstruction – all of which challenge existing control architectures and mechanisms. This conference paper outlines the current challenges, requirements and applications. We will summarise recent satellite cluster developments and impacts on routing, signaling and frequency assignment problem, and where research for future integrated satellite-terrestrial networking is required.

Jan Latal
Implementation of VLC within a public lighting network
J. Latal, T. Stratil, S. Hejduk, F. Sarlej, J. Kolar, L. Hajek, and A. Vanderka
Department of Telecommunications, Faculty of Electrical Engineering and Computer Science, VSB-Technical University of Ostrava, Czech Republic
The aim of this article is an introduction of implementation of VLC (Visible Light Communication) into a public lighting network within a testbed in the campus of VSB–Technical University of Ostrava. Using SoC (System on a Chip) and software, a fully functional system has been created and then implemented into street lamps in order to accomplish successful communication and lightning of the defined area. The goal of this article is to use RS232 serial communication for transmitting data via visible light of street lighting. This article describes the created electronic circuits and the results from testing.

Erich Leitgeb
Characteristics of ultra-long deep space FSO downlinks using special detector technologies like SNSPD
H. Ivanov and E. Leitgeb
Graz University of Technology, Austria
Free Space Optics (FSO) communication technology substantially increases its presence in the growing satellite constellations as well as for deep space applications. While NASA has already performed an enhanced FSO data transfer between Moon and Earth within Lunar Laser Communication Demonstration (LLCD), the current work provides an overview over a demonstration of deeper space optical links reaching planets Mars and Venus (that is partly accomplished in frame of ESA’s Hybridised Optical/RF Payload Data Transmitter study). By means of Poisson point processes, the introduced space-to-ground downlink is simulated in Matlab programming language and in a later phase, it is modeled with a self-developed laboratory testbed (implementing also different atmospheric effects and influences). In order to comply with CCSDS standards, the high-photon efficiency communication downlink relies on N-array Superconducting Nanowire Single-Photon Detector (SNSPD) unit, which is analyzed by means of its phenomenological model. Along with BER performance, the dependence on SNSPD’s recovery time and array size as well as Pulse Position Modulation (PPM) order and adverse atmospheric conditions are investigated, plotted and verified. The consistence of the theoretical predictions with the real downlink are tested based on laboratory FSO testbed investigating the performance of a 2-array SNSPD receiver unit. Apart from the SNSPD, an approach with space-to-ground downlink emulator based on fibre-coupled Variable Optical Attenuator (VOA) and a few fixed attenuators, which reproduce a Poisson channel (faced by adverse atmospheric effects), is considered and analysed. The provided real SNSPD characterization clearly shows the level of agreement with the simulation outcomes.
Keywords: Free Space Optics (FSO), Superconducting Nanowire Single-Photon Detector (SNSPD), Poisson point processes, Poisson channel, space-to-ground downlink, laboratory FSO testbed.

Mario Rannello
Investigating the potential of the Hydron network
E. Ciaramella¹, G. Cossu¹, M. Rannello¹, and V. Schena^2
1Scuola Superiore Sant’Anna, Pisa, Italy
²Thales Alenia Space, Roma, Italy
We present the system analysis of a new high-speed free-space optical network that should connect the various types of satellites (LEO, MEO and GEO) by means of high speed links, realizing the vision indicated as Hydron network. The paper will summarize key features of the different links and provide preliminary design rules.

Anand Srivastava
A smart user-centric visible light communication system
A. Singh¹, Y. Gupta¹, A. Bansal¹, A. Srivastava¹, V. A. Bohara¹, and A. K. Jagadeesan^2
1Department of Electronics and Communication Engineering, New Delhi, India
²Cognizant, Chennai, India
This paper presents a smart user-centric visible light communication (VLC) system for indoor communication application. In the proposed system, the VLC transmitter is incorporated with a barrier detection circuit which automatically detects the barrier between the VLC transmitter and receiver and dynamically changes its spatial location in two dimensions (2D) in order to get good signal-to-noise-ratio (SNR) performance at the receiver. The experimental set-up of the proposed smart VLC transmitter with a barrier detection circuit consists of a micro-controller, ultrasonic sensor and low-resolution camera. Analytical expression to calculate the SNR at the receiver with blockage due to the barrier has been derived. It has been shown that high SNR could be maintained uniformly in the presence of blockage with fewer light-emitting-diodes (LEDs), by using simple hardware circuitry, irrespective of the location of the user.

Murat Uysal
An innovative FSO system design with automatic rotation and alignment for small cell backhauls
B. Kebapci^1,2 and M. Uysal^1
1Ozyegin University, Istanbul, Turkey
²Hyperion Technologies, Istanbul, Turkey
In 5G and beyond cellular networks, small cells will play a significant role to efficiently deliver high speed mobile broadband in urban areas with a high density of users. In addition to macrocells, it is expected that small cells will be widely used as a second layer for extended network coverage and improved data throughput. With its operation in unlicensed optical spectrum and high capacity, free space optical (FSO) communication is uniquely positioned as an effective solution for small cell backhauling. In this paper, we present a custom-design FSO system with automatic rotation feature that allows the steering of the transceiver according to traffic capacity and facilitates the creation of mesh networks. It is also equipped with an automatic alignment sub-system based on the combined use of a multitude of sensors for coarse alignment and image processing techniques for fine alignment. After we describe the system architecture and implementation details, we will present our initial performance results of this custom-design FSO system based on a two-months measurement campaign for a 100 meter link conducted on the university campus.

Yuhui Wu
Analysis of the impact of misaligned wireless backhaul links on optical attocell networks
Yuhui Wu, M. Pickavet, and D. Colle
IDLab, Department of Information Technology, Ghent University-IMEC, Ghent, Belgium
Wireless solutions based on visible light communication (VLC) have been proposed for backhaul transmission in optical attocell networks. Perfect alignment of auxiliary transceivers is important for wireless backhaul links due to the requirement of direct line-of-sight (LOS) and the first-bounce specular reflection of mirror-aided non-LOS. However, the perfect alignment may not be guaranteed due to the limitation of the layout of BSs or installation mistakes. In this article, we investigate the impact of misalignment on the overall network performance. Two VLC backhaul link configurations have been considered and compared. Performance of using different frequency reuse schemes and channel allocation schemes are compared.

Changyuan Yu
Conceptual design for indoor visible light communication and positioning cooperative systems
Changyuan Yu¹, Xiaodi You², Zhongxu Liu¹, and Jian Chen^3
1Department of Electronic and Information Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong
²School of Electronic and Information Engineering, Soochow University, Suzhou, China
³School of Telecommunications and Information Engineering, Nanjing University of Posts and Telecommunications, China
Recently, how to achieve simultaneous high-speed data transmission and accurate positioning has been an interesting topic. Under the indoor illumination environment, the cooperation between visible light communication (VLC) and visible light positioning (VLP) has attracted increasing attention. In this paper, we review our recent proposed conceptual designs, which can realize cooperative VLC and VLP functionalities. By utilizing receiver location information, a location-based equalization (LBE) method is proposed for indoor VLC, where location-based equalizers are designed to compensate for multi-path channel distortion. By utilizing the estimated channel state information (CSI) during VLC process, a CSI-based VLP scheme is proposed, where the distances information between transmitters and the receiver can be extracted from received signals to enable VLPs. In order to integrate VLC and VLP within the same system, the spread-spectrum plugin of optical identification is inserted into the existing VLC frame structure to avoid signal mutual interference without breaking the existing VLC protocol. Keywords: Visible light communication, visible light positioning, cooperative design.

 

PAM invited presentations:

Mario Armenise
Coupled ring resonators at Fibonacci frequencies
C. Ciminelli, G. Brunetti, A. D’Amico, and M. N. Armenise
Optoelectronics Laboratory, Politecnico di Bari, Italy
Fibonacci (FB) numbers can be found in several domains of Science, such as biology, physics, astrophysics, chemistry, engineering and technology. In all systems, the fulfilment of FB series expresses the minimum energy configuration. In Ref. [1], some properties of the electronic systems are related to the FB numbers. In 2018, D’Amico et al. [2] have demonstrated FB relations in ladder networks made by sequences of directly coupled inductor-capacitor single cells. In an optical domain, also the properties of resonant structures can exhibit a FB-like behaviour in analogy with the coupled electrical resonant cells. Here, we propose a configuration of photonic coupled ring resonator, as the Coupled-Resonator Optical Waveguides (CROWs), properly designed in order to achieve resonance frequencies spaced according to the FB series. The device consists of two silicon-based coupled ring resonators [3], with same radius of 4.59 µm and a coupling coefficient between ring-bus and ring-ring of about 65%. The electromagnetic behaviour of the proposed device has been simulated by using the mathematical model reported in [4]. The resonance frequencies of the transmission spectrum correspond to the sequence: 1.002∙ω₀, 1.018∙ω₀, 1.022∙ω₀, 1.038∙ω₀ …, where ω₀ is the operating angular frequency [rad/s]. A device with similar peculiarities is suitable for several applications, e.g. quantum cryptography [5]. Cryptography enables two persons to exchange a message so that unauthorized persons cannot corrupt or take over the original message, and therefore providing a robust security service. Since the BB84 protocol [6], the quantum cryptography is becoming a powerful tool for information security. As photons allow a high spatial control and experience negligible decoherence through free space or fibers, they result the most suitable approach to deliver information [7]. Simple encryption techniques can safeguard the content of any information. Among them, the FB series result an emerging approach in the information security. In particular, in a classical Alice-Bob system based on single photon source, the proposed device could manipulate the photons so that Bob receive information encoded in frequency according to the FB series.
[1] G. Ferris, M. Faccio, A. D’Amico, “A new numerical triangle showing links with Fibonacci numbers,” Fibonacci Q., 29, 316–321, 1991.
[2] A. D’Amico, et al., “Resonant directly coupled inductors–capacitors ladder network shows a new, interesting property useful for application in the sensor field, down to micrometric dimensions,” Micromachines, 9, 343, 2018.
[3] S. K. Selvaraja, et al., “Highly uniform and low-loss passive silicon photonics devices using a 300mm CMOS platform,” Optical Fiber Communication Conference, Th2A-33, 2014.
[4] A. Yariv, “Critical coupling and its control in optical waveguide-ring resonator systems,” IEEE Photonics Technology Letters, 14, 483-485, 2002.
[5] A. K. Ekert, “Quantum cryptography based on Bell’s theorem,” Physical Review Letters, 67, 661, 1991; C. H. Bennett, G. Brassard, “Quantum cryptography: Public key distribution and coin tossing,” Theor. Comput. Sci., 560, 7-11, 2014.
[6] F. Flamini, N. Spagnolo, F. Sciarrino, “Photonic quantum information processing: A review,” Reports on Progress in Physics, 82, 016001, 2018.

Fang Bo
Multiple nonlinear optical effects in on-chip periodically-poled lithium niobate microdisks
Fang Bo, Li Zhang, Zhenzhong Hao, Guoquan Zhang, and Jingjun Xu
MOE Key Laboratory of Weak-Light Nonlinear Photonics, TEDA Institute of Applied Physics and School of Physics, Nankai University, Tianjin, China
Periodically poled lithium niobate (PPLN) microresonators with high quality factors provide a platform for efficient nonlinear optical effects due to the utilization of the largest nonlinear optical coefficient d₃₃ of lithium niobate (LN) and the enhancement of light-matter interaction. Here, we report the fabrication of PPLN microdisk resonators from lithium niobate on insulator (LNOI). The LN disks formed by optical lithography and argon ion etching are periodically poled by applying an electric field with the help of a piezo response force microscopy. This fabrication method can produce PPLN microresonators with a complicated domain pattern with cell size down to hundreds of nm. As an example, double-period PPLN microdisk resonators with a 2.4×10⁵ quality factor and a domain size of ~100 nm were fabricated. Benefiting from the multiple reciprocal vectors provide by the double-period PPLN microdisk, a series of nonlinear optical signals, such as second harmonic, third harmonic, and forth harmonic, were observed under the pump of a 1550-nm continuous laser. The normalized conversion efficiency of SHG reaches 5.1 × 10^-4 mW^-1.

Lev Deych
The role of magnetodipole corrections on the spectra of spheroidal whispering gallery mode resonators interacting with nanoparticles
L. Deych and Lan Yang
City University of New York, USA
An optical interaction between whispering gallery modes and nanoparticles is usually described assuming that the particle can be treated as a polarizable dipole. However, for larger particles, and especially for particles with high refractive indexes the magnetodipole contribution may start playing a role. In this paper we elucidate the spectral effects of the magnetodipole corrections to the field of the nanoparticle and show that even for low-refractive index particles the magnetodipole terms start playing an important role at much smaller particle sizes than it was anticipated. We pay special attention, however, to the case of high-refractive index particles, when the magnetodipole response takes a form of a broad Mie resonance in the visible part of the spectrum and can be made to overlap with the narrow WGM resonance of the main resonator. The corresponding spectral effects are discussed.

Chunhua Dong
Non-reciprocity in the multi-mode optomechanical microresonator

Patrice Féron
Whispering gallery mode erbium-doped laser: Studies on modal-coupling
P. Féron, J.-B. Ceppe, L. Ruel, C. Pareige, and Y. Dumeige
Université de Rennes, CNRS, Institut FOTON – UMR 6082, Lannion, France
Whispering gallery mode (WGM) resonators have been subject to many studies in the last decades. Despite the various types of WGM lasers studied, there is a severe lack about WGM laser dynamics experiments. In high finesse cavities, backscattering effects leads to a coupling between waves travelling in opposite directions. This modal-coupling by Rayleigh backscattering [1] can be used for the detection of single particles below [2] and beyond laser threshold [3], but experiments on the laser dynamic in such a regime hasn’t been performed. We report an experimental study of Erbium-doped glasses whispering gallery mode (WGM) micro-spheres under laser oscillation and submitted to modal-coupling between co- and counter-propagating waves. Based on previous works [4], the signature of this effect lies in the Relative Intensity Noise (RIN) spectrum of the WGM laser. Correlations between coupled WGM are performed in order to know the emission regime and compared to well-known solid-state gyro-laser behaviour.
[1] D. Weiss et al., Optics Letters, 20, 1835 (1995).
[2] M. R. Foreman et al., Adv. Opt. Photon., 7, 168 (2015).
[3] L. He et al. Physical Review A, 82, 053810 (2010).
[4] J.-B. Ceppe et al., Optics Express, 25, 32732 (2017).

Takehiro Fukushima
Resonance modes extremely sensitive to the asymmetry of cavity shape
T. Fukushima, Department of Information and Communication Engineering, Okayama Prefectural University, Japan
In 1958, Roger Penrose proposed an interesting two-dimensional geometry (known as the Penrose unilluminable room) which always has dark regions unreachable by optical rays regardless of where a point light source is set within the cavity. In the present work, the dependency of resonance modes on the asymmetry of the cavity shape of the Penrose unilluminable room was investigated using numerical calculations based on the finite element method. It was found that there exist resonance modes which are extremely sensitive to the asymmetry of the cavity shape. The formation mechanism of these resonance modes can be explained by the modal interaction between two resonance modes confined in different cavity regions.

Tetsuo Kishi
Glass microspheres with add-on structures for optical resonators
T. Kishi¹, T. Kumagai¹, H. Tang¹, S. Murai², G. Yuan², F. Prudenzano³, and T. Yano^1
1Tokyo Institute of Technology, Japan
²Kyoto University, Japan
³Politecnico di Bari, Italy
Tellurite glass microspheres having whispering gallery modes (WGMs) were fabricated on a substrate by using a localized-laser heating technique, and nano- or micro-structures were added on the microspheres to modify the resonance modes. Efficient coupling between the modes inside microspheres and pumping light was realized by the add-on structure; terrace, bubble, or plasmonic array. We fabricated an Nd3+-doped tellurite glass microsphere laser on a substrate by using a localized laser heating technique. The microsphere was pumped by free-space direct pumping of a tunable continuous-wave Ti: sapphire laser with a wavelength of 780 to 830 nm. The terrace structure acted as an entrance of the pumping light for the microsphere to decrease the laser threshold, and reduce the number of the laser emission laser peaks. The bubble structure also decreased the laser threshold and showed numerous peaks at a broad wavelength range in the excitation spectra due to non-degenerated WGMs. The microsphere laser on a plasmonic array modified both emission and excitation spectra. The highest-intensity laser emission mode was changed, and numerous peaks on a broad wavelength range were also observed. These results indicate that the add-on structures were useful for efficient utilization of broadband light like light-emitting diode and sunlight into laser light due to the modification of WGMs in a true sphere.
Keywords: whispering gallery mode, optical resonator, tellurite glass, plasmonic array.

Femius Koenderink
Collective resonances of plasmonic metasurfaces as an experimental platform for nonlinear and non-Hermitian physics
R. Kolkowski, S. Kovaios, A. Berkhout, S. Roscam Abbing, C. Dieleman, and A. F. Koenderink
Center for Nanophotonics, AMOLF, Amsterdam, the Netherlands
Metasurfaces are two-dimensional arrays of coupled resonant nanostructures designed for controlling various aspects of light scattering and light emission. In our research, we focus on plasmonic metasurfaces composed of metallic nanoantenna arrays supporting dispersive lattice resonances. We present theoretical and experimental examples of synergy between these lattice resonances and active media, which include enhancement of two-photon excited luminescence and its application to interferometric autocorrelation, and breaking parity-time symmetry in arrays with spatially engineered gain and loss, which opens new perspectives for distributed feedback lasing and active light shaping.

Vladimír Kuzmiak
Resonant scattering from a non-Hermitian two-dimensional honeycomb PT dipole structure
V. Kuzmiak¹ and P. Markos
¹Institute of Photonics and Electronics, Academy of Sciences of the Czech Republic, Praha, Czech Republic
²Department of Experimental Physics, Faculty of Mathematics Physics and Informatics, Comenius University in Bratislava, Slovakia
We numerically investigate the scattering properties of the finite periodic structure consisting of the PT dipoles represented by gain/loss cylinders arranged in a 2D honeycomb lattice. In the far field limit, the structure scatters an incident EM wave with arbitrary frequency is scattered only in a few directions given by spatial symmetry of periodic structure and the total scattered energy reveals series of sharp resonances at which the energy increases by two orders of magnitude. We interpreted both features in terms of the complex band structure associated with an infinite honeycomb array of the PT dipoles which supports a spontaneously broken PT-symmetric phase at the symmetry points and along the ΓK and ΓM directions. An existence of a complex conjugate pair offers a plausible explanation to both a significant enhancement of the radiated power as well as to highly-directional scattering pattern along the relevant symmetry directions.

Guoping Lin
Recent advances in monolithic nonplanar ring oscillators
Guoping Lin¹ and Yaqin Cao^2
1Ministry of Industry and Information Technology Key Lab of Micro-Nano Optoelectronic Information System, and School of Science, Harbin Institute of Technology, Shenzhen, China
²MOE Key Laboratory of Fundamental Physical Quantities Measurement, PGMF and School of Physics, Huazhong University of Science and Technology, Wuhan, China
Monolithic nonplanar ring oscillators are reliable narrow-linewidth continuous-wave laser sources in fundamental researches and practical applications, which have been successfully used in several satellite missions. In this talk, we report on recent developments on such laser sources. We show that high order Laguerre-Gaussian modes carrying orbital angular momentum can emit directly using a regular Gaussian pump beam. In particular, we demonstrate that these oscillators can work not only in the single-frequency lasing regime but also in the dual-frequency lasing regime with low phase noise performance.

Guowei Lu
In situ optical study of single plasmonic resonator coupling with two dimensional materials
Guowei Lu, Aiqin Hu, Te Wen, Weidong Zhang, Lulu Ye, and Qihuang Gong
Department of Physics, Peking University, Beijing, China
This study is about in situ optical study of single plasmonic resonator coupling with two dimensional materials (including monolayer graphene and transition metal dichalcogenides). Combing single particle spectroscopy and atomic force microscopy nanomanipulation technique provide a flexible way to reveal the interactions between nanoresonator and two dimensional materials. The resonant scattering amplitude and peak of the hybrids, coherent energy transfer rates between the plasmonic resonator and 2D materials were investigated. In addition, the coupling spectral features were dependent on their separation owing to the resonant energy transfer effect. These results bring us deep understanding to coherent interaction between plasmon and 2D materials.

Stuart Murdoch
Temporal cavity solitons in optical microresonators and fiber resonators
Yiqing Xu^1,2, Yi Lin³, A. Nielsen^1,2, I. Hendry^1,2, S. Coen^1,2, M. Erkintalo^1,2, Huilian Ma³, and S. G. Murdoch^1,2
1The Dodd-Walls Centre for Photonic and Quantum Technologies, Auckland, New Zealand
²Department of Physics, University of Auckland, Auckland, New Zealand
³School of Aeronautics and Astronautics, Zhejiang University, Hangzhou, China
Temporal cavity solitons (CS) are ultrashort pulses of light that persist in coherently driven passive Kerr resonators. They maintain their profile via a delicate double balance between the system’s dispersion and nonlinearity, and its driving and loss. As such, cavity solitons belong to the wider class of dissipative solitons. They were first experimentally demonstrated in macroscopic fiber resonators, and more recently have been observed in optical microresonators where they have been shown to generate broadband coherent frequency combs. This discovery has created considerable interest, especially for telecommunications applications, as it has opened up new prospects for on-chip frequency comb sources. We present results that show that cavity solitons can co-exist simultaneously in the same cavity, and each can be independently excited, erased, or manipulated. Because of this, they are also considered to be ideal candidates for optical bits in all-optical signal processing applications. We also discuss cavity solitons generated in Kerr microresonators synchronously driven with short pump pulses. In this regime we show it is possible to discretely tune the frequency spacing of the output comb.

Gualtiero Nunzi Conti
All-optical photoacoustic sensing with hollow microresonators
G. Frigenti^1,2, L. Cavigli¹, F. Ratto¹, S. Centi¹, A. Fernandez-Bienes³, T. Garcia-Fernandez⁴, S. Pelli¹, S. Soria¹, and G. Nunzi Conti^1
1Istituto di Fisica Applicata “Nello Carrara”, Consiglio Nazionale delle Ricerche, Sesto Fiorentino, Italy
²Laboratorio Europeo di Spettroscopia Nonlineare, Università degli Studi di Firenze, Sesto Fiorentino, Italy
³Facultad de Ingeniería, Universidad Nacional Autónoma de México, Mexico City, Mexico
⁴Universidad Autónoma de la Ciudad de México, , Mexico City, Ciudad de México, Mexico
We developed an all-optical photoacoustic (PA) sensing platform based on whispering gallery mode (WGM) hollow resonators able to detect plasmonic nanoparticles in microfluidics. A silica microbubble resonator (MR) made on a capillary and exhibiting high optical and mechanical Q factors acts as a unique ultrasound transducer for photoacoustic characterization of metallic nanoparticles. The system was tested with gold nanorods (GNR) placed inside the MBR and acoustic detection was achieved by monitoring the enhanced modulation of the optical resonances at the microbubble mechanical eigenfrequencies.

Jiří Petráček
Edge states in strongly coupled photonic waveguide arrays
J. Petráček^1,2 and V. Kuzmiak^3
1Faculty of Mechanical Engineering, Brno University of Technology, Czech Republic
²Central European Institute of Technology, Brno University of Technology, Czech Republic
³CAS, Institute of Photonics and Electronics, Prague, Czech Republic
Photonic waveguide arrays represent convenient systems in which the evolution of the waves in complex structures can be studied. It has been shown that by engineering of the propagation constants of the individual waveguides and their mutual couplings one can explore a rich variety of quantum-optical analogies. In the paper we will focus on various types of edge states (ES) supported by the arrays. Theoretical description of ES is usually based on the coupled mode theory (CMT). However, it is well known that CMT is valid only in the limit of weak coupling, which may not be fulfilled in modern nanophotonic and/or plasmonic structures. Therefore, in the paper we will investigate the limits of CMT in such strongly coupled, high-index-contrast systems. Finally, we will discuss the effect of strong coupling on the existence of ES.

Raimondas Petruškevičius
Hybrid micro-ring resonators for enhanced hydrogen sensing
R. Petruškevičius¹, T. Rakickas¹, S. Matsuura², D. Kezys¹, A. Balčytis^1,2, S. Okazaki², T. Arakawa², Y. Nishijima², and R. Valiokas^1
1Center for Physical Sciences and Technology, Vilnius, Lithuania
²Graduate School of Engineering, Yokohama National University, Yokohama, Japan
We report on an optical hybrid platform for hydrogen gas sensing that is based on tungsten oxide (WO₃) nanoparticles as hydrogen absorbing material and silicon-on-insulator (SOI) micro-ring resonators (MRRs). The latter consisted of fabricated first order Bragg grating 1D photonic crystals to enhance the light-matter interaction and the sensitivity of the gas sensors. We performed local functionalization of such perforated MRRs by the lipid flow-enhanced dip-pen nanolithography technique. For this, we formulated the ink based on the mixtures of phospholipids and WO₃ nanoparticles. The recent results on modeling, fabrication and characterization of the hybrid perforated MRRs hydrogen sensors are presented. Such hybrid WO₃/MRR-based sensors are promising for simple and rapid prototyping of SOI integrated devices that are highly sensitive to hydrogen gas.
Keywords: nanophotonics, hydrogen, WO₃ nanoparticles, lipids, micro-ring resonators, gas sensor, dip-pen nanolithography, rapid prototyping.

Alexander Smirnov
Multipolar second-harmonic generation from high-Q quasi-BIC states in nanoresonators
A. I. Smirnov, Institute of Applied Physics, Russian Academy of Science, Nizhny Novgorod, Russia
Multimode interference and multipolar interplay govern functionalities of optical nanoresonators and nonlinear nanoantennas. Recently, excitation of the high-quality supercavity modes (quasi-BIC states) in individual subwavelength dielectric particles has been predicted to boost the nonlinear frequency conversion at the nanoscale. Here, we put forward the multipolar model which captures the physics behind linear and nonlinear response driven by such high-Q modes in nanoresonators. We show that formation of the quasi-BIC state in the AlGaAs nanodisk can be understood through multipolar transformations of coupled leaky modes. In particular, the hybridized axially symmetric TE-polarized modes can be viewed as superpositions of multipoles, with a basis of parent multipoles constituted mainly by magnetic dipoles and octupole. The quasi-BIC point in the parameter space appears where dipolar losses are totally suppressed. The efficient optical coupling to this state is implemented via azimuthally polarized beam illumination matching its multipolar origin. We establish a one-to-one correspondence between the standard non Hermitian coupled-mode theory and multipolar models that enables transparent interpretation of scattering characteristics. Using our approach, we derive the multipolar composition of the generated second-harmonic radiation from the AlGaAs nanodisk and validate it with full-wave numerical simulations. Back-action of the second-harmonic radiation onto the fundamental frequency is taken into account in the coupled nonlinear model with pump depletion. A hybrid metal-dielectric nanoantenna is proposed to augment the conversion efficiency up to tens of per cent and actualize the nonlinear parametric downconversion. Our findings delineate the in-depth conceptual framework and novel promising strategies in the design of functional elements for nonlinear nanophotonics applications.

Silvia Soria Huguet
Whispering gallery mode resonators as physical, chemical and biochemical sensors
G. Frigenti^1,2, D. Farnesi¹, F. Baldini¹, S. Berneschi¹, A. Giannetti¹, L. Lunelli³, L. Pasquardini³, M.-Pilar Marco⁴, C. Pederzolli³, G. C. Righini¹, S. Pelli¹, G. Nunzi Conti¹, and S. Soria^1
1CNR-IFAC “Nello Carrara” Institute of Applied Physics, Sesto Fiorentino, Italy
²Laboratorio Europeo di Spettroscopia Nonlineare (LENS), Università degli Studi di Firenze, Italy
³FBK-CMM, Trento, Italy
⁴Nanobiotechnology for Diagnostics group (Nb4Dg), IQAC-CSIC,-Barcelona, Spain
Many novel approaches based on different optically resonant platforms have been developed for the detection of antibodies and aptamers. We report the use of microspherical whispering gallery mode resonators (WGMR), solid and hollow, combined with label and label-free techniques for the detection of IgG. Regarding the aptasensing application, we studied silica microspherical WGMR in a label-free approach. The microspheres were first functionalized with an epoxy silane then we immobilized an orienting layer (protein G) and finally we covalently bonded IgG labeled with tetramethyl rhodamine isothiocyanate (TRITC) for the label approach. The quality factor of the microspheres was over 10⁶ after the functionalization procedure. Regarding the label-free approach we functionalized first using Eudragit for IgG detection. For the aptasensor case, we functionalized the surface with mercaptopropyltrimethoxysilane (MPTMS). Two different thrombin specific aptamers and one vascular endothelial growth factor (VEGF) specific aptamer were then immobilized on resonator. Hollow microresonators or microbubble resonators combine the unique properties of whispering gallery mode resonators with the intrinsic capability of integrated microfluidics. Microbubbles were filled with water and aqueous solutions of ethanol in order to test the refractive index sensing capabilities of such resonators. We observed two photon fluorescence in microbubbles filled with a 10^-6 M solution of Rhodamine 6G. The microbubble diameter was about 510 µm, with a Q factor of about 5×10⁷. All measurements were performed in a modified confocal microscope; we coupled the excitation light with a 10× objective and detected the TPF signal with a CCD. The pump laser is a femtosecond Ti:Sapphire (Coherent). The fluorescent signal shows a nonlinear dependence on the pump power, as expected. These results show the great potential of WGMR for nonlinear detection of biological material and organic compounds. Regarding physical sensors, we used different types of microresonators as pressure sensors, thermal sensors and ultrasound transducers.

Misha Sumetsky
Recent progress in the development and applications of SNAP technology
M. Sumetsky, Aston Institute of Photonic Technologies, Aston University, Birmingham, UK
Since its introduction in 2011, Surface Nanoscale Axial Photonics (SNAP) technology – which enables the fabrication of nanoscale-shallow complex high Q-factor microresonator structures at the surface of an optical fiber with subangstrom precision – exhibited noticeable theoretical and experimental development. In this presentation, I briefly review the theory and fabrication principles of SNAP microresonators and then proceed with recent results obtained in 2018-2020. In particular, I review new fabrication technique of droplet-induced microresonator structures in optical capillaries, microresonators induced by bending of optical fibers, precise relative tuning of coupled microresonators, and slow-cooked microresonators. Next, I discuss our recent experiments on resonant tunneling through a SNAP microresonator and tunneling and slow propagation of light near a cut-off wavelength of a uniform optical fiber. Finally, I discuss the potential applications of SNAP for the fabrication of miniature delay lines, microlasers, frequency comb generators, optomechanical microdevices, optical buffers, and single photon microprocessors.

 

PhotoMAN invited presentations:

Pierpaolo Boffi
Exploitation of deployed telecommunication fiber infrastructures for sensing applications
I. Di Luch, M. Ferrario, G. Rizzelli, R. Gaudino, and P. Boffi
Politecnico di Milano, Dept. Electronics, Information and Bioengineering – PoliCom Lab, Milan, Italy
The optical fiber infrastructure deployed in our cities to support the communication networks is exploited for sensing applications, where the optical sensing signals co-propagate together with the telecom traffic. Thanks to a coherent interferometric approach, structural monitoring of buildings can be achieved in deployed passive optical networks based on fiber-to-the-home structure. Moreover, the same technology is experimented in urban fibre ring networks to detect and localize mechanical vibrations or dynamic perturbation. The proposed sensing solutions provide significant added value to the fiber infrastructure, that can turns into a simple and reliable embedded systems for optical surveillance, preventing dangerous damages to both urban buildings and the optical network infrastructure itself.

Giovanni Delrosso
Development and scalability of a 2Tb/s data communication module based on a 3um SOI silicon photonics platform
G. Delrosso and S. Bhat
VTT Technical Research Centre of Finland, Espoo, Finland
VTT’s well-proven 3 μm SOI photonic integration platform is particularly suitable for passive optical functionalities such as (de-)multiplexer, power splitters, delay lines, and Mach-Zehnder interferometers, and also for active operations such as phase tuning through thermo-optic switches, and optical power monitoring and high-speed detection with integrated Ge photo-detectors. In combination with integrated up-reflecting 45° mirrors and cavities with solder topographies to improve heterogeneous integration of III-V actives, both wafer level packaging and E/O wafer level tests can be fully exploited, scaling up in volume manufacturing while dramatically reducing assembly costs. Here heterogeneous integration of 40 InP VCSELs around 1.55 μm in the ITU 100-GHz grid, directly modulated at 50Gb/s, flip-chip coupled on the 3 μm SOI Si-PIC, which is essentially a 100 GHz spaced 1x40 channel MUX, forming a 40-channel transmitter module, with respective 40 linear drivers and digital interfaces embedded into a Land Grid Array Interposer, is reported.

Juan Fernandez-Palacios
Zero touch metro optical networks using sliceable bandwidth variable transponders
J. P. Fernandez-Palacios, V. Lopez Alvarez, and J. D. Martinez Jimenez
Telefonica GCTIO, Spain
SBVTs (Sliceable Bandwidth Variable Transponders) enable transmitting from one point to multiple destinations, changing the traffic rate to each destination and the number of destinations on demand. The aim of this work is to quantify potential savings of SBVT based architectures calculated in relation to estimations for non-sliceable transponders of 100 Gb/s and 400 Gb/s. The techno-economic analysis considers accumulated CAPEX and OPEX costs in a 10 years period over a real network scenario in Hamburg region.

Ricardo Martínez
Design and deployment of a SDN programmable optical metro network with VCSEL-based S-BVTs
R. Martínez, R. Casellas, M. Svaluto Moreolo, J. M. Fabrega, R. Vilalta, R. Muñoz, and L. Nadal
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Castelldefels (Barcelona), Spain
To cope with the stringent requirements of upcoming optical metro networks (i.e. huge transport capacity, low cost, power efficiency, and programmability), this work discusses the designed and developed SDN controller to enable the programmability of the EU-H2020 PASSION project metro network solutions. These exploit appealing technologies and innovations such as VCSEL-based S-BVTs and hierarchized flexi-grid optical switching nodes to dynamically accommodate different data-rate connections

Gabriel Otero
Strategies to scale edge computing throughout the MAN with optical networking technologies
G. Otero Pérez¹, D. Larrabeiti López¹, J. A. Hernández Gutiérrez¹, J. P. Fernández-Palacios², V. López², M. Svaluto Moreolo³, J. M. Fabrega³, and L. Nadal^3
1Universidad Carlos III de Madrid, Spain
²Telefónica Global CTO, Spain
³Centre Tecnològic de Telecomunicacions de Catalunya(CTTC), Castelldefels, Spain
Dense metropolitan areas are responsible for the majority of the traffic growth in telecom operators. The focus of the EU H2020 PASSION project is to develop new photonic technologies for supporting agile metro networks and enabling capacities of Tb/ s per channel to deal with such traffic increment, with a particular focus on two components (1) the Sliceable Bandwidth Variable Transceivers and (2) Pb/s optical switches. This paper analyses two strategies from the perspective of computation resource consumption: overflow over a paired same-level DC and overflow over a centralized site. We present a methodology to compare both schemes and prove that a proper distribution of computing resources in the centralized overflow together with S-BVT high-speed transmission can outperform the costs of a distributed strategy, requiring fewer processors and much smaller DCs in COs.

Paola Parolari
Preliminary assessment of photonic solutions based on C-band VCSELs for multi-Tb/s metro networks
P. Parolari¹, A. Gatto¹, M. Rapisarda¹, F. Lipparini¹, C. Neumeyr², M. Svaluto Moreolo³, and P. Boffi^1
1Dip. Elettronica Informazione e Bioingegneria, Politecnico di Milano, Italy
²VERTILAS GmbH, Garching, Germany
³Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Castelldefels, Spain
C-band InP vertical cavity surface emitting laser (VCSEL) exploitation can be appealing also for high-capacity transmission over hundreds of kilometres. We present preliminary experimental assessments of directly modulated VCSEL sources with multi-carrier modulation formats, for more than 50 Gb/s per-channel transmission over a metro network including nodes, handling 25-GHz granularity.

Netsanet Tessema
Modularly integrated photonic switches for metro core and access network for 5G applications
N. Tessema, K. Prifti, A. Rasoulzadehzali, S. Bhat, G. Delrosso, R. Stabile, and N. Calabretta
Technische Universiteit Eindhoven (TU/e), The Netherlands
We report the passion approach for the implementation photonic switching in the metro core and access networks for 5G application. Network capacity requirements are met by modular design in a pay-as-you grow manner. Scalability is enabled by low-loss switching via both monolithic and hybrid integration techniques

 

PICAW invited presentations:

Theoni Alexoudi
Multiple I/Os waveguide-based frontend design for beam steering operation
D. Ketzaki¹, G. Patsamanis², K. Vyrsokinos², and T. Alexoudi^1
1Department of Informatics, Centre for Interdisciplinary Research and Innovation, Aristotle University of Thessaloniki, Greece
²Department of Physics, Centre for Interdisciplinary Research and Innovation, Aristotle University of Thessaloniki, Greece
Recently, research attention has focused into integrated solutions with Waveguide Frontend (WFE) circuits instead of conventional fiber frontends for on-chip beam transforming functions in Wavelength Selective Switches (WSSs) and Transponder Aggregator (TPA) configurations. These integrated WFEs can reduce the bulky free-space components together with the associative cost and footprint while allowing for tighter integration of I/Os. Moving towards advanced switching systems such as TPAs requires upgraded functionalities such as beam transforming combined also with beam steering by the respective integrated circuits. In this communication we extend our previous work on InP-based WFEs and present our recent progress on the design concept and operating principle of an InP-based WFE with multiple I/Os that can emit and receive multiple beams allowing for both beam transforming and steering operation. The proposed circuit can in turn enable the combination of multiple WSSs maximizing in this way the gain in integration density brought by the WFEs in hybrid TPAs.
Keywords: beam transforming, optical passive devices and modules, photonic integration, photonic integrated circuits.

Eugene Avrutin
High power 1.5 µm pulsed semiconductor laser design with a bulk active layer and an asymmetric waveguide
B. S. Ryvkin^1,2, E. A. Avrutin³, L. W. Hallman¹, and J. T. Kostamovaara^1
1Dept of Electrical and Information Engineering, University of Oulu, Finland
²A. F. Ioffe Physico-Technical Institute, St. Petersburg, Russia
³Dept of Electronics, University of York, UK
InGaAsP/InP high pulsed power lasers operating in the range of 1.3-1.6 um have been intensely studied recently, with LIDAR technology being the primary application. We present and analyse a design with a bulk active layer which has a large refractive index step with respect to the optical confinement layer and is located close to the p-cladding. It is shown that such lasers can allow a noticeable performance increase over the state of the art. The dependence of the laser performance on the design parameters including the thicknesses of the active layer and the waveguide, the cavity length, and the waveguide asymmetry, is analysed. It is shown that short cavity lengths (~1 mm or even shorter) can be used in the design considered for achieving high pulsed power. Due to the significant waveguiding properties of the active layer, the use of both symmetric and asymmetric waveguide designs is possible, with only slightly higher output predicted for the asymmetric one. Both designs allow operation with a single, broad transverse mode enabling high brightness.

Antoine Brimont
Low voltage silicon photonic modulators and switches for high radix integrated transmitters
A. Brimont¹, A. Zanzi¹, C. Vagionas², M. Moralis Pegios², K. Vyrsokinos², N. Pleros², J. Kraft³, V. Sidorov³, B. Sirbu⁴, T. Tekin⁴, and P. Sanchis^1
1Nanophotonics Technology Center, Universitat Politècnica València, Spain
²Aristotle University of Thessaloniki, Greece
³ams AG, Premstaetten, Austria
⁴Fraunhofer Institute for Reliability and Microintegration (IZM), Berlin, Germany
In this paper, we summarize the latest results on silicon electro-optical (E/O) modulators in the framework of the European project L3MATRIX. The (E/O) devices were fabricated in a 0.350µm CMOS commercial production foundry (AMS AG) without recurring to CMOS-incompatible materials or processes deviating from ams AG foundry standards. Our symmetric O-band modulator and C-band switch designs were based on alignment-tolerant vertical pn junctions with high doping concentrations such that a high priority is given to low voltage operation enabled by the high modulation efficiency around 3.2V.mm. First, the 1.25mm-long lumped electrode switch operates under 0.6V peak-to-peak differential voltages and ≈1 ns rise/fall times. Beyond-1Vpp operation allows smaller switching time values due to capacitance reduction. Moreover, the 0.93mm-long travelling-wave (TW) modulators operates at 8Gbps with 1.6V peak-to-peak differential voltage as specified by the maximum output voltage of the control IC (1.8V). 10 Gbps modulation is achieved with higher swing voltages (2.3Vpp) to circumvent the bandwidth limitations likely due to the capacitive nature of the modulator as well as the electrode design. Finally, enhanced O-band slow light modulators are explored.
Keywords: silicon E/O modulators, integrated E/O switches, slow light, pn junction, carrier depletion modulators.

Jean-Emmanuel Broquin
Glass integrated photonic platform: Passive, active and hybrid devices for telecommunications and sensors
J.-E. Broquin, E. Ghibaudo, D. Bucci, A. Morand, J. Poette, and L. Bastard
Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, Grenoble INP, IMEP-LAHC, Grenoble, France
Glass integrated photonics is a mature technological platform that has allowed realising many devices with applications not only in telecom but also in sensors. In this presentation, we will review the evolution of this technology at IMEP-LaHC over the last decade. The fundamentals of the technology will first be presented as well as the performances of the realised waveguides. Passive and active devices like integrated spectrometers, DFB and pulsed lasers and harsh environment sensors will be detailed. Finally, a focus will be made on current developments and perspectives concerning 3D integration and hybrid devices combining other technological platforms (Silicon, LiNbO3…) with the glass one.

Nicola Calabretta
Novel photonic integrated circuits for optical datacom and telecom networks
M. Mamun, S. Mukit, B. Pan, X. Xuwei, K. Prifti, S. Cardarelli, and N. Calabretta
IPI-ECO Research Institute, Eindhoven University of Technology, The Netherlands
We present novel photonic integrated circuits with broadband operation for low cost and low power consumption optical data center and telecom networks. Full process, polarization independent operation, and system performances will be investigated and validated by experimental results. The novel photonic integrated circuits enable novel disaggregate and scalable optical data center architectures as well as dynamic metro access switching nodes with edge computing functionalities.

Stéphane Calvez
Progress in interband cascade lasers: From edge emitting lasers to VCSELs
S. Calvez¹, O. Stepanenko¹, D. A. Diaz Thomas²,T. Batte³, M. Bahriz², C. Paranthoen³, E. Tournie², C. Levallois³, A. Baranov², G. Almuneau¹, and L. Cerutti^2
1LAAS-CNRS, Toulouse, France
²IES, University Montpellier, CNRS, Montpellier, France
³University of Rennes, INSA, CNRS, Institut FOTON, Rennes, France
Mid-infrared lasers are crucial devices to enable optical spectroscopy in this spectral region of strategic importance for molecular sensing. In this presentation, we will review our recent progress in mid-infrared sources based on interband cascade active regions for operation in the L-band (wavelength of ~3.4 µm) and in particular towards the demonstration of VCSELs, the most promising laser embodiment for energy-efficient portable tunable sources.

Maurizio Casalino
Silicon meet graphene for a new family of near-infrared resonant cavity enhanced photodetectors
M. Casalino, T. Crisci, L. Moretti, M. Gioffrè, M. Iodice, G. Coppola, P. Maccagnani, R. Rizzoli, F. Bonafè, C. Summonte, and V. Morandi
Institute for Microelectronic and Microsystems, Italian National Research Council, Napoli, Italy
We present design, fabrication and characterisation of a free-space silicon-graphene Schottky photodetector operating at 1550nm and integrated with a Si-based optical microcavity. The photocurrent generation is based on the internal photoemission effect, where photoexcited carriers from graphene are emitted to silicon over a potential Schottky barrier that exists at the graphene-silicon interface. The graphene absorptions is strongly increased by the multiple reflections inside the Fabry-Perot microcavity. We demonstrate that our photodetectors show performance which start becoming comparable with germanium technology.

Reinhard Caspary
Disruptive impact of digitalisation on optical technologies
R. Caspary, Cluster of Excellence PhoenixD Leibniz University Hannover, Germany
There are many indications, that the 21st century will be the century of optics and photonics. In the last century microelectronics established many technologies which show increasing impact on the field of optical technologies like silicon photonics or optoelectronics. However, the success of microelectronics was accompanied by the rise of information technologies and their impact on the optical technologies could be even more significant. Digitalisation leads to disruptive developments like lensless imaging through turbid media and holographic imaging. Machines are no more limited to traditional camera images optimized for humans. Instead, hyperspectral imaging improves the usefulness of machine vision substantially. Digitalisation also has a great impact on production technologies and meanwhile industrial additive manufacturing reaches the sub-wavelength range. This allows for the production of individualized diffractive optical elements. An interesting application example is optical machine learning for real-time pattern recognition.

Pavel Cheben
Metamaterial-inspired integrated photonics
P. Cheben¹, J. Schmid¹, R. Halir², A. Ortega-Moñux², A. Sánchez-Postigo², J. G. Wanguemert-Pérez², I. Molina-Fernández², D. González-Andrade², J. Čtyroký³, A. V. Velasco⁴, A. Herrero-Bermello⁴, J. M. Luque-González², D. Pereira-Martín², A. Hadij Elhouati², P. Ginel Moreno², D. Benedikovic⁵, C. Alonso-Ramos⁵, L. Vivien⁵, J. Lapointe¹, S. Janz¹, D.-X. Xu¹, D. Melati¹, W. Ye⁶, Y. Grinberg¹, S. Wang¹, M. Vachon¹, M. Kamandar Dezfouli¹, R. Cheriton¹, M. Dado⁷, J. Mullerova⁷, and J. Litvik^7
1National Research Council, Ottawa, Canada
²ETSI Telecomunicación, Universidad de Málaga, Spain
³University of Paris Sud, CNRS, Univ. Paris Saclay, Paris, France
⁴CSIC and Universidad Complutense de Madrid, Madrid, Spain
⁵University of Žilina, Slovak Republic
⁶Institute of Photonics and Electronics, the Czech Academy of Sciences, Prague, Czech Republic
⁷Carleton University, Ottawa, Canada
The availability of nanometer scale fabrication techniques has inspired scientists to investigate subwavelength-structured metamaterials with engineered optical properties. Metamaterial waveguide devices are becoming established as fundamental building blocks for the next generation photonic integrated circuits. Here we present an overview of recent advances in this surging field, including metamaterial fiber-chip couplers, ultra-broadband telecom components, waveguide sensors, polarization splitters, anisotropy engineered nanophotonic structures, complex spectral filters and surface emitting nanoantennas.
[1] P. Cheben, R. Halir, J. H. Schmid, H.A. Atwater and D.R. Smith, Subwavelength integrated photonics, Nature 560, 565-572 (2018).
[2] R. Halir, A. Ortega-Moñux, D. Benedikovic, G.Z. Mashanovich, J. Gonzalo Wangüemert-Pérez, J.H. Schmid, Í. Molina-Fernández, and P. Cheben, “Subwavelength-grating metamaterial structures for silicon photonic devices,” doi: 10.1109/jproc.2018.2851614, Proceedings of the IEEE (2018).

Sébastien Cueff
Functional materials enabling integration of active modulation on silicon nitride platform
A. Taute^1,2, L. Berguiga², S. Monfray¹, X. Letartre², and S. Cueff^2
1STMicroelectronics, Crolles, France
²Institut des Nanotechnologies de Lyon (INL), CNRS UMR5270, Villeurbanne, France
Silicon nitride is a material that has garnered a strong interest in the fields of photonics thanks to its wide transparency range, allowing for visible to mid-infrared applications. One of the drawbacks of this platform is the difficulty to achieve active functionalities in silicon nitride: because of its dielectric nature, plasma dispersion modulation is impossible. Thermo-optic modulation, although possible, is substantially less efficient than in silicon because of the low thermo-optic coefficient of silicon nitride. In this communication, we will present different functional materials that could be integrated on the silicon nitride platform to enable active modulation properties. These materials were characterized in the visible and near-infrared range using ellipsometry. Simulation tools, using the measured optical properties, are then used to determine the applicability of these materials. We further present future targeted devices and different potential applications of this heterogeneous platform.

Alexander Fuerbach
Towards all-integrated mid-infrared light sources
A. Fuerbach, G. Bharathan, S. Rehman, L. Xu, and T. Fernandez
Department of Physics and Astronomy, Macquarie University, Sydney, Australia
We report on our research into the development of compact, robust and field-deployable laser systems in the mid-infrared spectral region. This specific part of the electromagnetic spectrum has long attracted much scientific and technological interest due to the fact that virtually all molecules have their rotational-vibrational absorption lines in this range. For this reason, the mid-infrared is often referred to as the “molecular fingerprint” region. Owing to the high-impact applications that result from the strong molecule-photon interaction, such as trace molecular detection for airport security screening and non-invasive breath analysis, mid-IR photonics has become one of the hottest topics in modern optics research. While virtually all current mid-infrared laser sources heavily rely on bulk-optical components and are consequently complex and sensitive systems that are restricted to be used in a vibration temperature and humidity-controlled laboratory environment, our research aims at developing all integrated hybrid fibre/chip sources with high brightness.

Kevin Gallacher
Ge-on-Si mid-infrared waveguide platform for molecular fingerprint sensing
K. Gallacher¹, R. W. Millar¹, U. Griskeviciute¹, M. Sinclair¹, M. Sorel¹, L. Baldassarre², M. Ortolani², R. Soref³, and D. J. Paul^1
1University of Glasgow, James Watt School of Engineering, UK
²Dipartimento di Fisica, Universita di Roma La Sapienza, Italy
³Engineering Program, University of Massachusetts at Boston, USA
The mid-infrared spectral region is key to several large market applications such as security, healthcare and environmental monitoring. This is due to how chemical compounds can be detected from unique vibrational modes that absorb in the molecular ‘fingerprint’ region (6.7-20 µm wavelength). There is significant interest in realizing cheaper and smaller spectrometers based on waveguide integrated photonics. Here we demonstrate Ge-on-Si waveguides operating up to 11 µm wavelength with low propagation loss (~ 1 dB/cm). The performance of the waveguides is then demonstrated by measuring thin films that are used to calibrate the modal overlap for molecular sensing. Lastly, an ultra-broadband Ge-on-Si waveguide polarization rotator is presented. The fabricated devices demonstrate a polarization extinction ratio of ≥ 15 dB over a 2 µm bandwidth (9-11 µm wavelength) with an average insertion loss ≤ 1 dB.

Kambiz Jamshidi
An overview of integrated photonic devices for energy efficient transmitters used in optical interconnects
K. Jamshidi, S. Sabouri, S. Dev, M. Catuneanu, and L. A. Mendoza Velasco
Integrated Photonic Devices Group, TU Dresden, Germany
In this paper, various components required for the realization of transmitters to be used for short-range optical interconnects are presented and their performance is studied using either numerical simulation or lab measurements. Optical modulators, thermos-optic phase shifters, and frequency combs are investigated in this article.
Keywords: optical modulators, silicon photonics, thermal tuning, frequency comb.

Eva Kempf
Low temperature SiN waveguides optimization for photonic platform
E. Kempf^3,1, M. Calvo^1,3, F. Domengie³, S. Monfray³, F. Boeuf³, P. Charette², and R. Orobtchouk^1
1Institut des Nanotechnologies de Lyon (INL), CNRS UMR5270, INSA de Lyon, Villeurbanne, France
²Laboratoire Nanotechnologies Nanosystèmes (LN2)-CNRS UMI-3463, Université de Sherbrooke, Québec, Canada
³STMicroelectronics, Crolles, France
Integration of SiN on Si photonics platform becomes attractive for 3D integration of different waveguide levels in an optical routing circuit. As the thermal conductivity and the refractive index contrast with silica is lower than the one with silicon, it can be used for the realization of athermal devices or circuits needing specifics group index or group velocity dispersion. Low propagation losses can also be obtained with high thermal annealing close to 1100°C. This paper is focused on the determination of the optical properties of different SiN deposited by PVD (Plasma Vapor Deposition) and PECVD (Plasma Enhanced Plasma Vapor Deposition) equipment with temperatures lower than 400°C to keep the compatibility with CMOS process. Optical routing basic building blocks such as bends and MMI splitters have been designed for the realization of a set of test devices allowing a high accuracy on the determination of propagation losses and propagation constants of the guided modes for a large spectral range between 1.2 to 1.7 µm [1]. Devices were manufactured on the STMicroelectronics DAPHNE (Datacom Advanced PHotonics Nanoscale Environment) 300 mm Photonic R&D platform [2]. Comparison of experimental data with theoretical models will be made. Especially, we discuss the development of Finite Difference Full Vectorial mode solvers [3-4] for straight and bend waveguides coupled with the Mode Matching method. Not only is this method used to simulate the propagation of light, but it also allows to evaluate side wall roughness contributions, Rayleigh scattering and absorption due to 2nd harmonic stretching vibrations of Si-OH and N-H bonds.
[1] G. Fan et al., “Optical waveguides on three material platforms of silicon-on insulator, amorphous silicon and silicon nitride,” IEEE J. Sel. Top. Quantum Electron. 22, 225 (2016).
[2] S. Guerber et al., “Integrated SiN on SOI dual photonic devices for advanced datacom solutions,” Silicon Photonics: From Fundamental Research to Manufacturing (Strasbourg, France), p. 3, (2018).
[3] X. Hu et al., “Modeling the anisotropic electro-optic interaction in hybrid silicon-ferroelectric optical modulator,” Opt. Express 23, 1699 (2015).
[4] M. Masi et al., “Towards a realistic modelling of ultra-compact racetrack resonators,” J. Lightwave Technol. 28, 3233 (2010).

Dimitra Ketzaki
Optical beam shaping through SiN-based waveguide arrays towards WSS front-ends
G. Patsamanis¹, T. Alexoudi², D. Chatzitheocharis¹, K. Vyrsokinos¹, and D. Ketzaki^2
1Department of Physics, Centre for Interdisciplinary Research and Innovation, Aristotle University of Thessaloniki, Greece
²Department of Informatics, Centre for Interdisciplinary Research and Innovation, Aristotle University of Thessaloniki, Greece
Wavelength Selective Switches (WSS) have emerged as the key elements in next generation reconfigurable optical add/drop multiplexed (ROADM) networks. Lately, on-chip beam transforming function is gaining traction for its use in WSSs as it can eliminate the need for precise alignment of complicated and expensive bulk optical components. So far, only monolithically integrated on a silica-based planar lightwave circuits (PLC) have been suggested for on-chip beam transforming in hybrid WSSs. In this work, we present an alternative design of an integrated beam transformer relying on SiN MMI-based frontend towards replacing traditional WSS front-end approaches.
Keywords: optical beam shaping, waveguide front-ends, photonic integrated circuits.

Kenji Kintaka
Retroreflection by cavity-resonator-integrated guided-mode resonance mirror
K. Kintaka¹, T. Kusuura², J. Inoue², and S. Ura^2
1National Institute of Advanced Industrial Science and Technology, Japan
²Kyoto Institute of Technology, Japan
A cavity-resonator-integrated guided-mode resonance mirror (CRIGM) consists of a grating coupler integrated in a waveguide resonator constructed of a pair of distributed Bragg reflectors on a high-reflection substrate. A narrowband retroreflection for an oblique incidence of 1540-nm wavelength was demonstrated by a CRIGM with 20-µm aperture.

Sylwester Latkowski
Photonic integrated circuits, from small batches to volumes: Standardization and automation of test
S. Latkowski, D. Pustakhod, M. Chatzimichailidis, X. Leijtens, and K. Williams
Photonic Integration, Eindhoven University of Technology (TU/e), The Netherlands
Scaling up Photonic Integrated Circuits from prototyping and small batch fabrication runs to volume production requires revision and improvements of processes across the full production chain. These efforts include test processes at front-end and back-end service providers, for example foundries and outsourced semiconductor assembly and test sites respectively. Recent developments of automated, prepackaging die test services, carried at Photonic Integration Technology Center and TU/e as a part of European pilot lines, PIXAPP and InPulse will be presented.

Julien Lumeau
Micro-structured thin-film optical elements for spectral filtering
D. Belharet¹, L. Robert¹, F. Lemarquis², A. Moreau², T. Begou², and J. Lumeau^2
1MIMENTO, FEMTO-ST, UMR 6174, Besançon, France
²Aix-Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France
The need for imaging systems for onboard scientific applications (e.g. for planetology) is becoming of prime interest. Today’s CCD scientific cameras do not provide spectral information of the observed scene. Multi-spectral imaging therefore requires the usage of filters wheels which allow achieving the required optical performances but are a heavy and bulky solution that make them non-adapted for space missions. The goal of this work consisted in developing pixelated filters that could be directly integrated in front of an onboard CCD camera in order to provide with the required spectral information without significantly changing the volume and the weight of the whole system. In this paper, we show the methods that were developed to produce of 2×2-array pixelated optical filters with 15 × 15 μm² pixel size. Four bandpass filters centered at 550, 700, 770 and 840 nm, 40 nm bandwidth and rejecting in a broadband from 500 to 900 nm were designed. These filters were then fabricated by a new sequential technique using deposition, masking and etching to secure sharp edges for each pixel. Local mapping of the transmission of each pixelated filter was finally carried out with a dedicated system. Comparative measurements between witness samples and filters prototypes show that the pixelated filters have performances comparable to the witness 25 mm aperture filters. This new technology therefore paves a way to the fabrication of multispectral imagers with versatile spectral specifications.

Jarmila Müllerová
Influence of multilayer design and post-deposition processing on effective photonic properties of silicon/silicon nitride multilayer structures
J. Müllerová¹, P. Šutta², P. Calta², R. Medlín², and M. Netrvalová^2
1Institute of Aurel Stodola, Faculty of Electrical Engineering and Information Technologies, University of Žilina, Slovak Republic
²New Technologies – Research Centre, University of West Bohemia, Plzeň, Czech Republic
Complex silicon systems with amorphous, polycrystalline or nanoparticles embedded multilayer structures are qualified to control light transmission and reflection. Therefore periodic silicon-based multilayers become subjects of interest for photonic-based applications such as solar cells, optical sensors, optical filters, grating couplers etc. In this paper photonic properties of different silicon/silicon nitride multilayers deposited by PECVD and post-deposition processed have been studied and compared. Results from optical transmittance spectroscopy have been used to determine dispersive and absorptive photonic properties (refractive indices, absorption coefficients and optical band gaps) of multilayers considered as effective thin films. Apparent modifications of effective photonic properties corresponding to a specific multilayer design and post-deposition annealing have been observed which is meaningful for absorption-related applications.

Pascual Muñoz
Sagnac reflector based broadband tunable integrated mirror
J. Fernandez, D. Domenech, L. Bru, D. Pastor, and P. Muñoz
VLC Photonics S.L., Valencia, Spain
In this work we present the design, fabrication and characterization of a variable Sagnac Loop Interferometer that can be employed as a tunable mirror. This is a key building block to be included in the implementation of folded devices in order to reduce their footprint. The improvement on the power consumption of variable couplers based on standalone Mach-Zehnder interferometers (MZIs) or MZIs with Sagnac Loop Reflectors is discussed as well. To assess the feasibility of the designed components, several configurations have been implemented in a Silicon Nitride platform and the results obtained are in good agreement with the theoretical developments carried out.

Antonio Napoli
800G over 1000 km enabled by real-time DSP ASIC employing probabilistic shaping and digital sub-carrier multiplexing
Han Sun, M. Torbatian, M. Karimi, R. Maher, S. Thomson, M. Tehrani, Yuliang Gao, A. Kumpera, G. Soliman, A. Kakkar, M. Osman, Z. A. El-Sahn, C. Doggart, Weikun Hou, S. Sutarwala, Yuejian Wu, M. R. Chitgarha, V. Lal, Huan-Shang Tsai, S. Corzine, Jiaming Zhang, J. Osenbach, S. Buggaveeti, Z. Morbi, M. Iglesias Olmedo, I. Leung, Xian Xu, P. Samra, V. Dominic, S. Sanders, M. Ziari, A. Napoli, B. Spinnler, Kuang-Tsan Wu, and P. Kandappan
¹Infinera Ottawa, Canada
²Infinera Munich, Germany
³Infinera Sunnywale, CA, USA
Application-specific integrated circuit (ASIC) is at the core of modern ultra-high speed transponders employing advanced digital signal processing (DSP) algorithms. Jointly to advanced transmission techniques, such as probabilistic shaping and digital sub-carrier multiplexing, it enables high capacity coherent transmission. In this invited contribution, we present our recent data-rate × distance record with experimental transmission of all real-time 800G channel over 1000 km in full C-band.

Virginie Nazabal
Infrared-sensor based on chalcogenide waveguide for detecting water pollution
M. Baillieul^1,2, E. Baudet^1,2, A. J. Gutierrez-Arrovo³, E. Rinnert², P. Nemec⁴, J. Charrier³, L. Bodiou³, J. Lemaitre³, F. Colas², K. Boukerma², C. Boussard-Pledel¹, B. Bureau¹, K. Michel⁵, and V. Nazabal^1,4
1Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes) – UMR 6226, Rennes, France
²IFREMER, Laboratoire Détection, Capteurs et Mesures, Unité Recherches et Dévelopements Technologiques, Plouzané, France
³FOTON, UMR CNRS 6082, Lannion, France
⁴Department of Graphic Arts and Photophysics, Faculty of Chemical Technology, University of Pardubice, Czech Republic
⁵BRGM, Direction Eau, Environnement et Ecotechnologies, Unité Bio-Géochimie environnementale et qualité de l’Eau, , Orléans, France
The development of sensor enabling in situ detection of organic molecules into water by means of optical method is a vast ecological challenge. The chemical molecules that spread in the water lead to high monitoring requirements: high stability, sensitivity, multiplexing opportunities, large sensing range, compactness and short response time. Due to the absorption phenomenon in the mid-infrared (MIR) range (2.5-25 µm) caused by the fundamental vibrational transitions of organic molecules, this spectral range turned into a key choice within bio-chemical sensing in the gas or liquid state. The potential of MIR photonics implementation is considerable including the (bio)-chemical sensors for environmental monitoring, security, and medical diagnostics. Among the various categories of optical sensor including the conventional attenuated total reflectance (ATR), the detection by means of evanescent field is one of the possible ways to allow the miniaturization of the sensor device with integration of mid-infrared photonic components and low-cost production. Chalcogenide glasses has attracted attention for sensing applications due to their wide transparency in the infrared range, their ability to be fabricated in thin film by PVD and manufactured into integrated photonic components by photolithographic and etching process. We will report the development of chalcogenide mid-IR platform devoted to mid-IR spectroscopy by means of evanescent wave. The choice of chalcogenide glass composition, the chalcogenide films synthesis through RF magnetron sputtering, the theoretical approach for defining the analytical design of the evanescent optical field sensor for detection of pollutants into water, the patterning of the films by means of photolithography and reactive ion etching, the optical losses and the surface functionalization of the sensor will be described. In this work, MIR-ATR spectroscopy was used for the detection of benzene, toluene, ortho-, meta-, and para- xylenes in a mixture in aqueous solutions. Poly-isobutylene and EP-co polymers were deposited to reduce the strong absorbance of water and to extract pollutant molecules from the solution. Regeneration of polymer film was demonstrated by pure water flow. Finally, several real natural waters i.e. groundwater, wastewater and seawater, were analyzed using MIR-ATR system and compared to results of the samples prepared in laboratory. These results represent a supplementary step towards the development of integrated optical sensor for the detection of organic molecules in water in the MIR spectral range. We will also present our last results on fabrication of rare earth doped chalcogenide waveguide for possible emission in mid-IR fluorescence.
The authors would like to acknowledge the LOUISE (ANR-15-CE04-0001-01), supported by French National Research Agency (ANR) for a financial support and also Britany Region, GACR Project No. 19-24516S.

Liam O'Faolain
SiN nanophotonics for lasers
L. O’Faolain, Cork Institute of Technology, University of St Andrews, Tyndall National Institute, UK
The indirect bandgap of Si results has made the realisation of efficient silicon-based lasers problematic. The preferred solution is now to integrate III-V materials on silicon to realise energy efficient lasers. We will describe our on work on Hybrid Integration – in which completed chips of III-V materials are bonded to a silicon chip using flip-chip assembly and on Transfer Printing – in which devices or dies of material are placed in the desired locations on the integration platform using the high-throughput, parallel and scalable technique of transfer using a polydimethylsiloxane stamp. These integration approach offers an independent optimization of the gain chip and Si chip during the design and fabrication phase. Our recent work on silicon nitride 1D and 2D photonic crystals for integration with the above III-V components will also be presented.

Markus Pollnau
Light intensity distributions in Bragg gratings and distributed-feedback resonators
J. Yeung and M. Pollnau
Advanced Technology Institute, Department of Electrical and Electronic Engineering, University of Surrey, Guildford, UK
Periodic optical structures are employed in numerous photonic applications. The coupled-mode theory was developed to calculate the electric-field distributions within such structures. However, for more complex, non-perfectly periodic optical structures it merely provides approximated solutions. The characteristic-matrix approach provides exact solutions but is cumbersome to apply. We introduce a simple method to obtain the exact electric-field and intensity distributions in an arbitrary multi-resonator structure by considering the structure as a combination of multiple Fabry-Pérot resonators of various lengths and refractive indices. The circulating-field approach can be applied recursively to obtain the electric-field distribution of such structures. As each resonator is considered separately, this method can be easily applied to structures with non-uniform resonator lengths and refractive indices, such as chirped and tapered gratings, thereby greatly simplifying their analysis. We apply this method to the calculation of reflectivity spectra and electric-field, intensity, and phase distributions of Bragg gratings and distributed-feedback (DFB) structures.

Joan Manel Ramirez
Heterogeneous III-V lasers on silicon: Fundamentals and applications
J. M. Ramirez¹, P. Fanneau¹, C. Besancon¹, H. Elfaiki¹, T. Verolet¹, D. Neel¹, N. Vaissiere¹, S. Malhouitre², V. Muffato², C Jany², A. Shen¹, C. Caillaud¹, J. Decobert¹, D. Bitauld¹, and K. Hassan^2
1III-V Lab, Palaiseau, France
²CEA LETI, Minatec, Grenoble, France
Semiconductor III-V lasers and optical amplifiers have driven enormous interest due to their key role on different applications including optical communications, sensing or real-time imaging, among others. Although the current InP platform provides reliable devices that perform in line with the specified demands, the technology remains costly and with a low-volume production. To surmount these limitations, new technologies are being explored to reduce the cost, scale-up the production and minimise the use of III-V raw materials. In that context, the heterogeneous integration of III-V materials on Si platforms rises up as an interesting alternative to match these goals. This approach benefits from the maturity level acquired by the silicon photonics during the last years, with state-of-the art components and devices with excellent performance, while strictly limiting the use of III-V materials to where active functions are needed. In this paper, we will present our most remarkable results on heterogeneous III-V lasers on silicon photonic platforms. In addition, we will revisit some fundamentals of lasers, along with a non-exhaustive review of current applications.
Keywords: heterogeneous integration, silicon photonics, lasers.

Jens Schmid
Applications of subwavelength silicon photonics for light coupling, spectral filters and optical nanoantennas
J. H. Schmid¹, P. Cheben¹, D. Melati¹, D.-X. Xu¹, S. Janz¹, J. Lapointe¹, M. Kamandar Dezfouli¹, R. Cheriton¹, Y. Grinberg¹, S. Wang¹, M. Vachon¹, R. Halir², A. Ortega-Moñux², G. Wangüemert-Pérez², I. Molina-Fernández², A. Sánchez-Postigo², D. Pereira-Martín², P. Ginel Moreno², and Jiří Čtyroký^3
1National Research Council Canada
²University of Malaga, Spain
³Institute of Photonics and Electronics, Prague, Czech Republic
Dielectric metamaterial waveguides with adjustable refractive index and birefringence can be synthesized by lithographic patterning at the subwavelength scale on a standard silicon photonics platform. This method has become a powerful design tool which has been applied to many silicon photonic devices such as fiber-chip couplers, waveguide crossings, microspectrometers, ultra-fast optical switches, athermal waveguides, evanescent field sensors, polarization rotators and colorless interference couplers. Here we review recent progress in the field and particularly report the development of silicon subwavelength engineered dielectric metamaterial structures for spectrally broadband light coupling to silicon waveguides, multi-line spectral filters and long nanoantennas for optical phased arrays. We demonstrate a prism assisted zeroth-order grating coupler with a bandwidth exceeding 125 nm, an evanescently coupled Bragg filter with 3-dB bandwidths down to 150 pm, complex multi-line filters and metamaterial waveguides acting as surface emitting nanoantennas with lengths of several millimeters.

Isaac Suárez
Role of self-absorption in the photoluminescence waveguided along CsPbBr₃ perovskite nanocrystals thin films
J. Navarro-Arenas¹, A. F. Gualdrón-Reyes², V. S. Chirvony¹, I. Mora-Seró², J. Martínez-Pastor¹, and I. Suárez^3
1Instituto de Ciencia de Materiales (ICMUV), Universidad de Valencia, Paterna, Spain
²Institute of Advanced Materials (INAM), University Jaume I, Castellón, Spain
³Escuela Técnica Superior de Ingeniería, Universidad de Valencia, Spain
During the last years, perovskite nanocrystals (PNCs) have been intensively studied as nanomaterials with excellent light absorption/emission properties. For example, PNCs have been successfully applied in solar cells, where the high absorption coefficient above the band gap increases the conversion efficiencies; or in optical sources, where the high quantum yield of emission at room temperature allows a low threshold of stimulated emission. In this scenario, an optical waveguide represents a suitable platform to enhance their electrooptical properties and to integrate different photonic functionalities. However, propagation of light along close packed films of PNCs is usually restricted to ~10 µm due to the high absorption efficiency above the bandgap and the scattering losses. In this work, we present an elegant integration of CsPbBr₃ PNCs in polymer waveguides that allows high generation of light together with propagation along long distances. In particular, we propose an ultrathin layers (50-100 nm) of close packed CsPbBr₃ PNCs sandwiched between two poly(methyl methacrylate) (PMMA) slabs. This configuration efficiently enhances the absorption and emission properties of the PNCs by the high confinement of the electromagnetic field within the active layer and allows the propagation over longer distances due to the absence of losses in the polymers. Since our experimental data reveals that light amplification threshold on this material only depends on the reabsorption, geometrical parameters in our structure are properly optimized to enhance the generation of light. These results provide a novel knowledge on the possible use of CsPbBr₃ inside waveguides and can pave the road of new optoelectronic devices based on PNCs.
Keywords: CsPbBr₃, waveguide, perovskite, light propagation, polymer, PMMA.

David Thomson
High performance silicon optical modulators
D. J. Thomson, W. Zhang, K. Debnath, B. Chen, K. Li, S. Liu, M. Ebert, J. D. Reynolds, A. Z. Khokhar, C. Littlejohns, J. Byers, M. K. Husain, F. Y. Gardes, S. Saito, and G. T. Reed
Optoelectronics Research Centre, University of Southampton, UK
High performance silicon optical modulators underpin a number of current and emerging applications based upon silicon photonic technology. Here we present our recent breakthroughs in this field.

Rolandas Tomasiunas
Fabrication of a new AlGaN/GaN-based multilayered waveguide structure for modal phase matching
R. Tomašiūnas, M. Kolenda, D. Kezys, I. Reklaitis, A. Kadys, T. Grinys, T. Malinauskas, and R. Petruškevičius
Institute of Photonics and Nanotechnology, Vilnius University, Lithuania
Optical integrated systems need optical frequency converters, certainly in a microscale. Most flexible and planar integrated are the second harmonic generation waveguides featuring modal phase matching. Not easy to fabricate, they deserve great attention from the technologists. The researchers and photonics specialists are keen to find new facets and implement them into new photonic circuits, devices. The full potential of applications is still to come, but there is a lot of work to develop the structures, investigate the features, accumulate experience. In this work, we present the fabrication of a GaN/AlGaN multilayer waveguiding structure with a dual GaN epilayer featuring planar polarity inversion dedicated to modal phase matching. On top of the AlGaN epilayer, in a role of a cladding layer, we fabricated the waveguiding structure starting with the MOCVD growth of the Ga-polar GaN epilayer followed by the atomic layer deposition (ALD) Al2O3 film, then, continuing with the MOCVD growth of N-polar GaN epilayer. We tested several film thicknesses to inverse the GaN polarity from Ga to N. We used atomic force and electron microscopes to analyze the interfaces of the waveguide, the XRD measurement to test the crystallinity of the epilayers. We will discuss challenges on the way to grow and test the complex multilayer structures dedicated to second-harmonic generation in the near-IR. This research was funded by the European Regional Development Fund according to the supported activity ”Research Projects Implemented by World-class Researcher Groups” under Measure No. 01.2.2-LMT-K-718 (Project code 01.2.2-LMT-K-718-01-0018).

 

PNPA invited presentations:

Cristian Antonelli
Nonlinear propagation in fibers for space division multiplexed transmission: Modelling and system impact
C. Antonelli, Università dell’Aquila, Italy

Daniele Bajoni
Generation of nonclassical light in silicon photonic structures under self-pumping
D. Bajoni, Università di Pavia, Italy

Lucia Caspani
Generation and characterisation of photonic cluster states on chip using frequency- and time-bin entanglement
L. Caspani, University of Strathclyde, Glasgow, UK

Matteo Clerici
Entanglement and quantum interference at 2100 nm
M. Clerici, Glasgow University, UK

Claudio Conti
Nonlinear photonics for neuromorphic computing and Ising machines
C. Conti, University of Roma, La Sapienza, Rome, Italy

Cid de Araújo
Glasses and nanopowders for lanthanide photonics
C. de Araújo, Universidade Federal de Pernambuco, Recife, Brazil

Olivier Gauthier-Lafaye
Using cavity resonator integrated grating filters for second harmonic generation
F. Renaud^1,2, S. Calvez¹, A. Monmayrant¹, E. Popov^2,3, A.-L. Fehrembach², and O. Gauthier-Lafaye^1
1LAAS-CNRS, Univ. de Toulouse, CNRS, Toulouse, France
²Aix Marseille Univ., CNRS, Centrale Marseille, Institut Fresnel, Marseille, France
³Institut Universitaire de France, France
Cavity Resonator Integrated Grating Filters are micro structured integrated resonators that exhibit resonances with Q factors in order of a thousand and that can be excited with focussed beams. These two characteristics make them particularly attractive as base components for nonlinear optical generation. In this contribution, we experimentally demonstrate second harmonic generation in such devices under continuous wave excitation and show that the measured performance are in good agreement with theoretical predictions.

Goëry Genty
Nonlinear dynamics in optics fibers: From real-time measurements to machine learning
G. Genty, Tampere University of Technology, Finland

Frédéric Grillot
Single state dynamics of InAs/GaAs quantum dot lasers: Stability, instability and chaos
F. Grillot, Institut Polytechnique de Paris, France & University of New-Mexico, USA

Wieslaw Krolikowski
Beam shaping in nonlinear volume holograms via optically engineered ferroelectric domain patterns
W. Krolikowski, Australian National University, Canberra, Australia

Sergey Mikhailov
Hot electrons and optical nonlinearities in graphene
S. Mikhailov, Universität Augsburg, Germany

Roberto Morandotti
Designing time and frequency entanglement for generation of high-dimensional photon cluster states (Keynote)
P. Roztocki¹, M. Chemnitz¹, B. MacLellan¹, S. Sciara^1,2, C. Reimer^1,3, M. Islam¹, L. Romero Cortes¹, Yanbing Zhang¹, B. Fisher¹, S. Loranger⁵, R. Kashyap^5,6, A. Cino², Sai T. Chu⁷, B. E. Little⁸, D. J. Moss⁹, L. Caspani¹⁰, W. J. Munro^11,12, J. Azana¹, M. Kues^1,4, and R. Morandotti^1,13
1Institut National de la Recherche Scientifique (INRS-EMT), Varennes, Canada
²Department of Engineering, University of Palermo, Palermo, Italy
³HyperLight Corporation, Cambridge, USA
⁴School of Engineering, University of Glasgow, Glasgow, UK
⁵Engineering Physics Department, Polytechnique Montreal, Montreal, Canada
⁶Electrical Engineering Department, Polytechnique Montreal, Montreal, Canada
⁷Department of Physics and Material Science, City University of Hong Kong, Hong Kong, China
⁸State Key Laboratory of Transient Optics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Science, Xi’an, China
⁹Centre for Micro Photonics, Swinburne University of Technology, Hawthorn, Australia
¹⁰Institute of Photonics, Department of Physics, University of Strathclyde, Glasgow, UK
¹¹NTT Basic Research Laboratories, NTT Corporation, Kanagawa, Japan
¹²National Institute of Informatics, Tokyo, Japan
¹³Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, China
The development of quantum technologies for quantum information science demands the realization and precise control of complex (multipartite and high dimensional) entangled systems on practical and scalable platforms. Quantum frequency combs (QFCs) generated via spontaneous four-wave mixing in integrated microring resonators represent a powerful tool towards this goal. They enable the generation of complex photon states within a single spatial mode as well as their manipulation using standard fiber-based telecommunication components. Here, we review recent progress in the development of QFCs, with a focus on our results that highlight their importance for the realization of complex quantum states. In particular, we outline our work on the use of integrated QFCs for the generation of high-dimensional multipartite optical cluster states and their uni-directional processing, being at the core of measurement-based quantum computation. These results confirm that engineering the time-frequency entanglement properties of QFC may provide a stable, practical, low-cost, and established platform for the development of near-future quantum devices for out-of-the-lab applications, ranging from practical quantum computing to more secure communications.
Keywords: quantum photonics, integrated nonlinear optics, fiber photonics, high-dimensional quantum states.

Jacopo Parravicini
Second harmonic generation with giant angular and spectral acceptance
J. Parravicini¹, L. Falsi², F. Di Mei², L. Tartara³, A. J. Agranat⁴, and E. DelRe^2
1Dipartimento di Scienza dei Materiali, Università di Milano, Italy
²Dipartimento di Fisica, “Sapienza” Università di Roma, Italy
³Dipartimento di Ingegneria Industriale e dell'Informazione, Università di Pavia, Italy
⁴Applied Physics Department, Hebrew University of Jerusalem, Israel
Frequency conversion and, more specifically, second harmonic generation, is a fundamental phenomenon in nonlinear optics, both for applications and fundamental research. The occurring of this last effect in crystals requires that the frequency-doubled propagating beam interferes constructively with the pump itself, a phase-matching (PM) condition which is due to momentum-conservation laws. These lead to wavelength-dependent constraints on the process geometry while the wavevector mismatch is accompanied by chromatic walk-off. Conversely, collinear PM in SHG can be obtained either through optical birefringence, which introduces wavelength and polarization constraints, and quasi-phase-matching, that requires periodic material microstructuring. We present the experimental demonstration of SHG with a spectral acceptance of more than 100 nm angular acceptance up to ±40°, with no polarization selectivity or chromatic walk-off. This is achieved in a disordered potassium-based perovskite manifesting giant broadband refraction (GR), which determines a natural and unconditioned PM with no chromatic walk-off. Results open the way to highly efficient versatile and adaptable nonlinear optical devices.

Lorenzo Pavesi
Intermodal four wave mixing for heralded single photon generations in the MIR
L. Pavesi, University of Trento, Italy

Varun Raghunathan
Nonlinear optics studies of emerging two-dimensional materials
V. Raghunathan, Indian Institute of Science, India

Concita Sibilia
Nonlinear optical properties of chiral metasurfaces
C. Sibilia, University of Roma La Sapienza, Rome, Italy

Silvia Soria
Microspherical resonators: From rainbow to phonon lasers
S. Soria, IFAC CNR, Firenze, Italy

Misha Sumetsky
Nonlinear surface nanoscale axial photonics (SNAP)
M. Sumetsky, Aston University, Birmingham, UK

 

Quantum Communications invited presentations:

David Bacco
Quantum communication with orbital angular momentum
D. Bacco, D. Cozzolino, B. Da Lio, Yunhong Ding, K. Rottwitt, and L. K. Oxenløwe
CoE SPOC, DTU Fotonik, Technical University of Denmark, Lyngby, 2800 Denmark
Quantum communication consists of the reliable transmission of quantum states among several parties toward the long-term goal of the Quantum Internet. Quantum Internet could open up a whole universe of new applications, spanning from fundamental physics and secure communications to remote quantum computing. Multiple degrees of freedom can be used for the distribution of the quantum states, such as polarization, frequency, time and space. In particular, Orbital Angular Momentum (OAM) of light is one of the most promising thanks to its unbounded nature, albeit challenging to manipulate. OAM has been largely investigated both for classical and quantum communications, allowing for example at enlarging the data rate in classical links and presenting a new base for high-dimensional states within quantum communication. Here, we report our recent results on related to the quantum states encoded in the orbital angular momentum of light proving the capability of preparing, manipulating, transmitting and measuring high-dimensional quantum states through a multimode fibre.

Konrad Banaszek
Phase stabilization in quantum-optical fingerprinting with coherent signals
M. Lipka^1,2, M. Jarzyna¹, M. Jachura¹, and K. Banaszek^1,2
1Centre for Quantum Optical Technologies, Centre of New Technologies, University of Warsaw, Poland
²Faculty of Physics, University of Warsaw, Poland
Phase stability is a critical factor affecting the efficiency of optical communication schemes relying on phase modulation. While quadrature detection allows for a relatively straightforward phase tracking at the receiver site, it cannot be directly applied to quantum-enhanced protocols which exploit photon counting in order to achieve improved performance in the regime of low optical power. An example is quantum fingerprinting which allows for the verification by a remote referee if two datasets held by Alice and Bob are identical with error probability below a given threshold. Compared to classical fingerprinting, the quantum protocol provides a reduction of the transmission time and an advantage in terms of number of data bits revealed to the referee¬ over its classical counterparts. Here, we demonstrate a phase-tracking technique based on photon counting which can be directly applied in practical implementation of quantum fingerprinting with power-limited optical signals and additive white Gaussian noise. Remarkably, the phase-tracking does not impose any modifications of the experimental setup at the cost of slight increase of the optical energy utilized by Alice and Bob. Importantly, the protocol maintains all the advantages offered by original quantum fingerprinting.

Hans Brunner
Precise noise calibration for CV-QKD
H. H. Brunner, S. Bettelli, Chi-Hang Fred Fung, and M. Peev
Huawei Technologies Duesseldorf GmbH, Germany
Continuous-variable quantum-key-distribution (CV-QKD) devices, conveniently based on standard components from the domain of coherent optical communication, can guarantee an information-theoretic secure-key expansion. Their security analysis assumes that all power lost in the channel, as well as channel noise in excess with respect to the shot noise, is due to an eavesdropper limited only by quantum mechanics. Quantifying the excess noise, which typically has significantly less power than the shot noise, is essential for secure-key generation. In this talk a heterodyne-receiver setup capable of measuring optical power with an extremely high sensitivity (approximately −130 dBm within a 12.5 MHz bandwidth at 1550 nm, corresponding to a power 40 dB below the shot noise) is analysed and demonstrated in a CV-QKD prototype device. Such accuracy is achieved by means of continuous calibration and long-time averages.

Virginia D’Auria
Hybrid entanglement between time-bin and wave-like encoding
É. Gouzien, F. Brunel, J. Etesse, S. Tanzilli, and V. D’Auria
Université Côte d’Azur, CNRS, Institut de Physique de Nice, France
We propose a scheme for the generation of hybrid states entangling a single photon time-bin qubit with a coherent state qubit encoded on phases. Compared to other reported solutions, time-bin encoding makes hybrid entanglement particularly well adapted to applications involving long distance propagation in optical fibres. This makes our proposal a promising resource for future out-of-the-laboratory quantum communication. In this perspective, we analyse our scheme by taking into account realistic experimental resources and discuss the impact of their imperfections on the quality of the obtained hybrid state.

Yunhong Ding
Quantum entanglement and teleportation based on silicon photonics
Yunhong Ding^1,2, D. Llewellyn³, I. I. Faruque³, D. Bacco^1,2, K. Rottwitt^1,2, M. G. Thompson³, Jianwei Wang^3,4, and L. K. Oxenlowe^1,2
1Department of Photonics Engineering, Technical University of Denmark, Lyngby, Denmark
²Center for Silicon Photonics for Optical Communication (SPOC), Technical University of Denmark, Lyngby, Denmark
³Quantum Engineering Technology Labs, H. H. Wills Physics Laboratory and Department of Electrical and Electronic Engineering, University of Bristol, UK
⁴State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing, China
Quantum entanglement and teleportation are the key resources building the backbone of quantum technologies, such quantum communications, quantum networks, and quantum computations. The quantum communication networks are based on long-range distribution of entangled photons and teleportation of photon qubit states. The resource efficient measurement-based quantum computing models relies on cluster entangled states and the teleportation of logical operations between qubit sites. Silicon provides a versatile platform for quantum information processing on chip, thanks to the CMOS-compatible fabrication process, ability to integrate thousands of components, and precise manipulation of quantum states on a single chip. Here we show our recent work on quantum entanglement and quantum teleportation technology based our advanced silicon photonics platform, a significant step towards future quantum network and optical quantum computing.

Ivan Djordjevic
Secure, global quantum communications networks
I. B. Djordjevic, University of Arizona, Department of Electrical and Computer Engineering, Tucson, USA

Veronica Fernandez
Correcting polarization degradation in free-space QKD systems
P. Arteaga-Díaz, M. Parra-Serrano, N. Denisenko, and V. Fernandez
Institute of Physical and Information Technologies, Spanish National Research Council (CSIC), Madrid, Spain
Prepare and measure quantum key distribution (QKD) schemes with polarization encoding require transmitter and receiver designs that minimize polarization degradation, i.e., unwanted changes in the state of polarization. In particular, high polarization extinction ratio (PER) signal states are important to achieve long-distance QKD, such as satellite-to-earth links, since polarization degradation in this case especially affects the secure key rate (SKR) due to the low signal-to-noise ratio caused by the large attenuation of the transmission channel. In this paper, we analyze the polarization degradation and its correction in the design of free-space QKD systems. The polarization of a wavefront can be degraded in two different ways: homogeneously, or inhomogeneously; the latter known as polarization aberrations. While homogeneous polarization degradation of the beam wavefront can be easily corrected with standard retardation plates, polarization aberrations are more complex and require a different correction approach. BB84 diagonal linearly polarized states are especially affected by polarization degradation as they get reflected off certain optical elements and its correction is essential to achieve low quantum bit error rates (QBERs). We have experimentally characterized the polarization degradation in a QKD transmitter and its impact in the final SKR and achieved an almost perfect correction of the diagonal linearly polarized states when choosing a specific optical design.
Keywords: free-space quantum key distribution, polarization degradation, polarization aberrations, polarization correction.

Rupesh Kumar
Feasibility of higher key rate continuous variable quantum key distribution with multi-mode signals
R. Kumar and T. Spiller
Quantum Communications Hub, Department of Physics, University of York, UK
This paper examines the feasibility of multi-mode Gaussian modulated continuous variable quantum key distribution (CV-QKD) systems for higher rate secure key generation at longer distances. We consider different multi-mode transmission scenarios and propose a feasible experimental set-up for a previously proposed multi-mode CV-QKD system with joint quadrature measurement. We compare signal to noise ratios (SNR) of multi-mode schemes and show many fold improvements in the joint quadrature detection based CV-QKD system.
Keywords: continuous variable quantum key distribution, multimode signal, signal to noise ratio.

Vicente Martin
A components based framework for quantum key distribution networks
V. Martin¹, D. Lopez², A. Aguado¹, J. Brito¹, V. Lopez², M. Peev^3
1Center for Computational Simulation and DLSIIS, Universidad Politécnica de Madrid, Spain
²Telefónica Investigacion y Desarrollo and gCTIO, Telefónica, Madrid, Spain
³Quantum Communications Lab. Huawei Research Germany, Dusseldorf, Germany
The difficulty of dealing with single-quantum processing and the inherent limitations of their transmission, be it absorptions or optical aperture, makes that current generations of Quantum Key Distribution (QKD) systems are essentially designed to work in a stand-alone mode on a single link. This limits their utility and the potential impact that in the market. To avoid these barriers, it is necessary to advance towards systems built for a network. Given the physical nature of quantum transmission, the QKD systems have to perform as network devices, and ideally on an equal footing, without requiring any specialized or ad hoc tuning. To achieve this “zero-touch” integration, it is necessary to build a software ecosystem. This software should take a bare QKD system and provide all the information, so that the network can manage and the applications use the system. Here we present a SW architecture, based on components with a well-defined functionality, to build the SW ecosystem needed to deploy QKD systems in networks. The components support classical and Software Defined Networks (SDN), as well as separated or integrated (sharing infrastructure) networks to improve their industrialization.

Vicente Martin
Quantum abstraction interface: Facilitating integration of QKD devices in SDN networks
R. B. Mendez¹, J. P. Brito¹, R. J. Vicente¹, A. Aguado¹, A. Pastor², D. Lopez², V. Martin¹, and V. Lopez^2
1Center for Computational Simulation, Universidad Politécnica de Madrid, Spain
²Telefonica gCTIO/I+D, Madrid, Spain
This work presents and implements Quantum Abstraction Interface (QuAI). QuAI is integrated in an SDN agent to enable the vendor agnostic configuration of QKD devices. The work demonstrates the framework to provide a flexible procedure to integrate QKD devices in production networks.
Keywords: quantum key distribution, software-defined networking, application program interface.

Giuseppe Patera
Theoretical aspects of quantum temporal imaging
G. Patera¹, D. B. Horoshko^1,2, J. Shi^1,3, and M. I. Kolobov^1
1Laboratoire PhLAM, Université de Lille 1, France
²B.I.Stepanov Institute of Physics, NASB, Minsk, Belarus
³University of Chinese Academy of Sciences, Beijing, China
Temporal imaging is a technique enabling manipulation of temporal optical signals in a manner similar to manipulation of optical images in spatial domain. The quantum description of temporal imaging is relevant in the context of long range quantum communication. Indeed this technology relies on the efficiency of quantum repeaters for which the temporal mode matching between the quantum emitters, the communication network and the quantum memories is critical. In this work we address the problem of temporal imaging of a temporally broadband squeezed light generated by a traveling-wave optical parametric amplifier. We consider a single-lens temporal imaging system formed by two dispersive elements and a parametric temporal lens, based on non-linear processes such as sum-frequency generation and four-wave mixing. We derive a unitary transformation of the field operators performed by this kind of time lens and evaluate the squeezing spectrum at the output of the single-lens imaging system. When the efficiency factor of the temporal lens is smaller than unity, the vacuum fluctuations deteriorate squeezing at its output. For efficiency close to unity, when certain imaging conditions are satisfied, the squeezing spectrum at the output of the imaging system will be the same as that at the output of the OPA in terms of the scaled frequency Ω’=MΩ which corresponds to the scaled time t’=t/M. The magnification factor M gives the possibility of matching the coherence time of the broadband squeezed light to the response time of the photodetector.

Armando Pinto
Quantum enabled private recognition of composite signals in genome and proteins
A. N. Pinto^1,2, L. Ortiz³, M. Santos⁴, A. C. Gomes⁵, J. P. Brito³, N. J. Muga¹, N. A. Silva¹, P. Mateus⁴, and V. Martin^6
1Instituto de Telecomunicações, University of Aveiro, Portugal
²Department of Electronics, Telecommunications and Informatics, University of Aveiro, Portugal
³Center for Computational Simulation, Universidad Politécnica de Madrid, Spain
⁴Departamento de Matemática, Instituto Superior Técnico, and Instituto de Telecomunicações, Lisboa, Portugal
⁵CBRA Genomics, Cantanhede, Portugal
⁶DLSIIS ETSI Informáticos and Center for Computational Simulation, Universidad Politécnica de Madrid, Spain
We present a quantum enabled secure multiparty computation service able to perform private recognition of composite signals. This system is based on the generation and distribution of quantum oblivious keys. The engineered system is going to be tested in the Madrid Quantum Network.
Keywords: quantum oblivious keys, quantum communications, secure multiparty computation.

Mohsen Razavi
The practicality of memory-based quantum communications systems
G. Currás Lorenzo, Yumang Jing, S. Sahu, and M. Razavi
School of Electronic and Electrical Engineering, University of Leeds, UK
One of the oldest solutions to efficiently extend the reach of quantum communications systems is to use quantum repeaters. Initial proposals for quantum repeaters all rely on quantum memory modules to store entangled states. Over the time, it has turned out that by trading the storage capabilities with quantum processing power, we can use quantum error correction techniques to reliably transfer quantum data. Nevertheless, memory-based solutions for quantum repeaters are still attractive and may appear earlier than the storage-free versions. In this talk, I go over some of the quantum communications systems that can benefit from existing to near-future quantum memory modules in their setup. This includes memory-assisted quantum key distribution systems in their finite key regime, as well as quantum repeater setups that use quantum repetition codes for entanglement distillation. In both cases, we specify the required system parameters that enable a meaningful advantage over relevant counterpart systems.

Nuno Silva
Practical Imperfections affecting the performance of CV-QKD based on coherent detection
N. A. Silva^1,2, D. Pereira^1,2, N. J. Muga^1,2, and A. N. Pinto^1,2
1Instituto de Telecomunicações – Aveiro, Portugal
²Department of Electronics, Telecommunications, and Informatics, University of Aveiro, Portugal
Continuous variable-quantum key distribution (CV-QKD) based on coherent detection has potential to be a cost-effective solution to deploy secure keys over optical networks. This is due to its compatibility with mature optical communication technologies, such as homodyne and heterodyne detection schemes. Nevertheless, realistic implementations of CV-QKD systems suffer from imperfections in the practical devices used to generate and detect the coherent states. Those imperfections deteriorate the performance of the CV-QKD system and can be exploited by an eavesdropper to steal key information without being detected. In this work, we discuss the impact of practical device imperfections on the excess noise of the CV-QKD and the achievable transmission distance. We also analyze the impact of detection imperfections on the measurement of the shot noise, and its impact on CV-QKD system security.

Domenico Tulli
Toward industry-ready, high-speed quantum random number generators
J. Martinez, F. Martin, C. Abellan, and D. Tulli
Quside Technologies S.L., Castelldefels (Barcelona), Spain
We live in a data-driven society driven by new technological developments such as IoT, artificial intelligence and block chain. Keeping up with new data sources across multiple environments creates new complexity at unprecedent scale. This unique technological evolution also corresponds to new cybersecurity and data-protection risks and challenges, which could ultimately impact users’ safety. Therefore, developing secure products and infrastructure with long-terms security guarantees is a global priority. Quantum technologies bring in a radically new toolset to realize unbreakable encryption systems as well as to improve randomized algorithms. However, the development of a reliable, high-speed, scalable QRNG for using it in production environments shows some challenges from both technological and industrial perspectives. In this talk, we present latest progress on scaling fast QRNGs based on the phase-diffusion scheme as well as advances in on-board metrological characterization of the devices for obtaining rigorous min-entropy (quality) bounds. We also review potential applications of these devices, both in cryptography and high-performance computing fields.

Alessandro Zavatta
Field trials of quantum key distribution in fiber links
D. Bacco¹, I. Vagniluca^2,3, and A. Zavatta^3,4
1CoE SPOC, DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, Kgs. Lyngby, Denmark
²Università degli Studi di Napoli Federico II, Napoli, Italy
³CNR-INO, Istituto Nazionale di Ottica, Firenze, Italy
⁴LENS, Università di Firenze, Firenze, Italy
In-field demonstrations in real-world scenarios boost the development of quantum key distribution (QKD) towards its integration in existing infrastructures. Although QKD devices are already adopted outside the laboratories, current field implementations still suffer from high costs and low performances, preventing this technology from a large-scale deployment in telecommunication networks. Here we present recent results that we obtained in two different scenarios: (i) using the submarine optical fiber channel between Malta and Sicily; (ii) in the metropolitan area of Florence (Italy), using a portion of the Italian quantum backbone which is a dark-fiber network connecting the entire Italian peninsula.

 

Quantum Photonics invited presentations:

Caterina Ciminelli
Silicon-based optical-pump rejection filter for quantum circuits
G. Brunetti, M. N. Armenise, and C. Ciminelli
Optoelectronics Laboratory, Politecnico di Bari, Italy
Since the first demonstration of photons entanglement in the early 1980s [1], the quantum optics has been a hot R&D topic for the scientific community. Several potential applications of the quantum optics have been investigated, as the quantum communication for the information security, the “sub-shot noise” measurements, and quantum computation and simulation with a greater computing power than the standard processors. In the early stage, the experiments were limited to “few-photons” and carried out by using discrete bulk optical elements, at the expense of a larger test bed and, then, scalable devices and systems [2]. In order to overcome these limitations, the integrated quantum photonics results a promising solution. In particular, the silicon-based photonics can be considered as a potential candidate to address the quantum photonics development because it offers the potential of a large scalability, the integration on the same substrate of several devices and the compatibility with the CMOS technology, something you cannot accomplish with the existing glass-based technology [3]. Silicon photonics results suitable to implement all stages of a quantum system, as sources, manipulation devices and receivers. In particular, for single photon generation, “atom-like” emitters, as “quantum dot” have been proposed in literature [4], while, for the two photons generation, the spontaneous four-wave mixing (SFWM) has already demonstrate efficient on-chip generation of entangled photons. Silicon-based microring resonators enhance the functionalities of SFWM and the features of the photon pairs sources, by reducing the footprint and increasing the light intensity [5]. Before the detection, the manipulation stage should be properly designed to implement the target functionality. As an example, Mach-Zehnder interferometers have been used at the transmitter and receiver sections to generate a secure quantum key in a quantum key distribution system. Furthermore, the suppression of the laser pump is an essential functionality of the manipulation stage. The filter aims to reduce, or even reject, the laser pump, whose intensity is larger than the photon-pair signal. In order to avoid any manipulations of the photon-pair signal, also allowing a short wavelength separation of the paired photons, a large suppression ratio with a very narrow rejection bandwidth is required. Several pump filter configurations have been proposed in literature, based on microring resonators and reflectors [6], contra-directional couplers [7] or cascaded MZIs [8]. Promising results have been obtained by Bragg grating configurations, as example, a silicon-based sidewall sub-wavelength grating, proposed in [9], shows a good compromise between the rejection bandwidth (1.1 nm) and the suppression ratio (> 40 dB). In this context, currently, we are investigating compact and innovative solutions, based on silicon/silicon-derived resonant cavities, aiming to obtain a very large suppression ratio with a narrow rejection bandwidth. In particular, we have designed a silicon-based optical-pump rejection filter to be used in quantum circuits for a variety of applications.
[1] A. Aspect, et al., “Experimental tests of realistic local theories via Bell’s theorem,” Phys. Rev. Lett., 470, 460–463, 1981.
[2] G. Masada, et al., “Continuous-variable entanglement on a chip,” Nature Photonics, 9, 316-319, 2015.
[3] A. Politi, et al., “Silica-on-silicon waveguide quantum circuits,” Science, 320, 646, 2008.
[4] P. Lodahl, “Quantum-dot based photonic quantum networks,” Quantum Science and Technology, 3, 013001, 2017.
[5] Q. Lin, and G. P. Agrawal, “Silicon waveguides for creating quantum-correlated photon pairs,” Optics Letters, 31, 3140-3142, 2006.
[6] C. Alonso-Ramos, et al., “Silicon-on-insulator single channel-extraction filter for DWDM applications,” IEEE 11th International Conference on Group IV Photonics (GFP), 219–220, 2014.
[7] R. Boeck, et al., “Grating-assisted silicon-on-insulator racetrack resonator reflector,” Optics Express, 23, 25509-25522, 2015.
[8] C. M. Wilkes, et al., “60 dB high-extinction auto-configured Mach-Zehnder interferometer,” Optics Letters, 41, 5318-5321, 2016.
[9] D. Pérez-Galacho, et al., “Optical pump-rejection filter based on silicon sub-wavelength engineered photonic structures,” Optics Letters, 42, 1468-1471, 2017.

Ortwin Hess
Control of semiconductor laser chaos through quantum chaos
O. Hess, The Blackett Laboratory, Department of Physics, Imperial College London, UK

Marco Liscidini
Engineering non-classical light in photonic integrated devices with linearly coupled and uncoupled resonators
L. Zatti and M. Liscidini
Dipartimento di Fisica, Università degli Studi di Pavia, Italy
Integrated micro- and nano-structures allow for the efficient generation of photon pairs via parametric fluorescence, thanks to the enhancement of the light-matter interaction associated with light confinement in small volumes. Yet the advantages of using integrated devices go well-beyond the sole efficiency improvement, for micro-structures grant an unprecedented control over the properties of the generated non-classical light. A particularly interesting case is that of structures composed of more than one micro-resonator. In these systems one can control the spectral properties of the generated light and suppress unwanted phenomena thanks to a careful engineering of the linear and nonlinear coupling of these resonant elements. In this talk we will review and compare a number of different solutions.

Ross Millar
Ge-on-Si single photon avalanche diode detectors with high detection efficiencies in the short-wave infrared
R. W. Millar¹, J. Kirdoda¹, K. Kuzmenko², P. Vines², Z. M. Greener², F. Thorburn², D. C. S. Dumas¹, L. Ferre-Llin¹, M. M. Mirza¹, G. S. Buller², and D. J. Paul^1
1University of Glasgow, James Watt School of Engineering, Glasgow, UK
²School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, UK
Single photon avalanche diodes (SPAD) detectors are devices that can time the arrival of single photons with picosecond precision. SPADs operating in the shortwave infrared are of particular interest for applications such as automotive LIDAR and Quantum Key Distribution. Here, we demonstrate a novel pseudo-planar geometry Ge-on-Si SPAD with 38% Single Photon Detection at 1310 nm wavelength (125 K), and a 50 fold improvement in noise-equivalent-power, compared to the prior-art. Ge-on-Si devices are found to have after-pulsing rates that are ~ 20% that of commercial InGaAs/InP devices when operated in identical conditions, highlighting the potential for increased photon counting repetition rates. The devices are compatible with Si foundry processing, meaning there is potential for low-cost devices compared to state-of-the-art InGaAs/InP SPADs.

Wolfram Pernice
On-chip manipulation and detection of single photons in lithium niobate nanophotonic circuits
E. Lomonte^1,2,3, F. Lenzini^1,2,3, M. Wolff^1,2,3, S. Ferrari^1,2,3, C. Schuck^1,2,3, and W. Pernice^1,2,3
1Institute of Physics, University of Münster, Germany
²CeNTech – Center for Nanotechnology, Münster, Germany
³SoN – Center for SoftNanoscience, Münster, Germany
As photonic devices continue to replace electronics in high-speed, low power and cost-effective signal processing applications, lithium niobate (LiNbO₃) has emerged as a material of choice due to its excellent electro-optic and nonlinear properties. However, conventional LiNbO₃ waveguides based on ion indiffusion suffer from the low refractive index contrast between core and cladding, resulting in bulky components. The recently developed Lithium-Niobate-On-Insulator (LNOI) technology has materialized as a promising platform for quantum information and telecommunication, allowing the possibility of monolithically integrate small footprint active components for the manipulation and detection of classical and quantum states of light on chip. Here we demonstrate compact, fast electrooptic modulators compatible with cryogenic temperatures combined with high-performance NbTiN superconducting nanowires single photons detectors (SNSPDs) on a single LNOI chip in a low loss, physically stable and scalable architecture.

Ganapathi Subramania
III-Nitride nanowire based photonics
G. Subramania, Sandia National Laboratories, Albuquerque, USA
Single or an array of III-Nitride nanowires can enable interesting nanophotonic devices in the visible regime which are important in areas such as solid-state lighting and quantum information science. Photonic crystals consisting of periodic or quasi-periodic arrays of such GaN nanowires containing InGaN quantum wells enable control of light emission properties such as beam emission profile to lasing threshold at visible wavelengths. Further, a broad range of emission wavelengths can be accessed through control of the photonic crystal periodicity. All of these, hinge on the fabrication of nanowires with high surface quality to minimize surface recombination which is achieved through a combination of wet and dry etching. Precisely, size-controllable quantum dots can also be fabricated in such nanowires through photoelectrochemical etching. We will discuss fabrication of photonic crystal and metasurfaces through above approaches as well as their optical response. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. The views expressed in the article do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Jürgen Volz
Correlating photons using the collective nonlinear response of atoms weakly coupled to an optical mode
J. Volz^1,2, P. Schneeweiss^1,2, A. Rauschenbeutel^1,2, A. S. Prasad², J. Hinney², S. Rind², S. Mahmoodian³, K. Hammerer³, and A. S. Sørensen^4
1Humboldt-Universität zu Berlin, Germany
²TU Wien-Atominstitut, Austria
³Leibniz University Hannover, Germany
⁴University of Copenhagen, 2100 Copenhagen, Denmark
Typical schemes for generating correlated states of light require a highly nonlinear medium that is strongly coupled to an optical mode. However, unavoidable dissipative processes, which cause photon loss and blur nonlinear quantum effects, often impede such methods. Here, I will report on a recent experimental demonstration of the opposite approach [1]. Using a strongly dissipative, weakly coupled atomic medium, we generate and study strongly correlated states of light [2]. Specifically, we study the transmission of resonant light through an ensemble of non-interacting atoms that weakly couple to a guided optical mode. Dissipation removes uncorrelated photons while preferentially transmitting highly correlated photons created through collectively enhanced nonlinear interactions. As a result, the transmitted light constitutes a strongly correlated many-body state of light, revealed in the second-order correlation function. The latter can be continuously be tuned from strong antibunching to bunching, depending on the optical depth of the atomic ensemble. The demonstrated mechanism opens a new avenue for generating nonclassical states of light and for exploring correlations of photons in non-equilibrium systems using a mix of nonlinear and dissipative processes. Furthermore, our scheme may turn out useful in quantum information science. For example, it offers a fundamentally new approach to realizing single photon sources, which may outperform sources based on single quantum emitters with comparable coupling strength [3].
[1] A. Prasad, J. Hinney, S. Mahmoodian, K. Hammerer, S. Rind, P. Schneeweiss, A. S. Sørensen, J. Volz, and A. Rauschenbeutel, submitted.
[2] S. Mahmoodian, M. Čepulkovskis, S. Das, P. Lodahl, K. Hammerer, and A. S. Sørensen, Phys. Rev. Lett. 121, 143601 (2018).
[3] European patent pending (PCT/EP2019/075386).

 

RONEXT invited presentations:

Marcelo Abbade
Spectral shuffling with phase encoding and dynamic keys applied to transparent optical network signals
W. Santos Souza¹, M. Pereira Nogueira¹, I. E. Lage Rodrigues¹, M. de Oliveira Santos¹, L. H. Bonani², I. Aldaya¹, and M. L. F. Abbade^1
1State University of São Paulo (UNESP), Brazil
²Universidade Federal do ABC (UFABC), Santo André, Brazil
A recently proposed signal encryption technique consists in shuffling the samples of two or more baseband signals, which are then modulated in different optical carriers and transmitted by transparent optical networks. In this work, we aggregate two new features to this approach: phase encoding and dynamic keys (DKs). Computer simulations are used to evaluate the novel encryption scheme that provides security against chosen plaintext attacks, without introducing significant bit error rate penalties to the shuffling technique. We also verify that the DK strategy offers cryptographic diffusion. Keywords: Physical layer security, signal processing, optical communications, optical networks.

Brigitte Jaumard
Linear formulation for the design of elastic optical networks with squeezing protection and shared risk link group
K. D. R. Assis¹, R. C. Almeida Jr², H. Waldman³, M. J. Reed⁴, B. Jaumard⁵, and D. Simeonidou^6
1Electrical Engineering Department, Universidade Federal da Bahia, UFBA, Brazil
²Electronic Engineering Department, Universidade Federal de Pernambuco, UFPE, Brazil
³Communications Department, Universidade Estadual de Campinas, UNICAMP, Brazil
⁴School of Computer Science and Electronic Engineering, University of Essex, UK
⁵Computer Science and Software Engineering Department, Concordia University, Montreal, Canada
⁶High Performance Networks Group and Smart Internet Lab, University of Bristol, UK
Elastic optical networking (EON) is fast becoming a key technology in the design of optical networks. Survivability is an important component in the requirements in EONs. We examine the significance of network survivability design against multiple-link failures under dedicated protection, shared risk link group (SRLG) and bandwidth squeezing schemes. We formulate the network survivability problem with the objective of minimizing the highest spectrum slot index. The proposed mixed integer linear programming (MILP) formulation seeks to derive some different types of protection considering routing, spectrum assignment, grooming, modulation format as well as shared risk link group constraints. The proposed MILP provides efficient survivability results and resource savings (in terms of spectrum) for a full design of modern EONs.

Ricard Vilalta
Transport network slices with security service level agreements
P. Alemany, R. Vilalta, R. Muñoz, R. Casellas, and R. Martínez
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC), Castelldefels, Spain
Security is a necessary field where there will be always a need to keep improving as fast as possible due to the increment of traffic and the possibility of cyberattacks. Network Slicing has been proved as a more resource-efficient mechanism when deploying network services over an optical network, but security mechanisms are needed in order to fulfill its view. This paper aims to join security and network slicing for transport networks by proposing a Network Slice Manager architecture with Security Service Level Agreement management included, in order to allow the network Slice requester to define which kind of security needs/desires.

 

SDM-WDM invited presentations:

Florian Azendorf
Group delay measurements of multicore fibers with correlation optical time domain reflectometry
F. Azendorf^1,2, A. Dochhan¹, F. Spinty¹, M. Lawin¹, B. Schmauss², and M. Eiselt^1
1ADVA Optical Networking SE, Meiningen, Germany
²LHFT, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
In this paper we present our latest research work on Correlation-Optical Time Domain Reflectometry (C-OTDR) of Multicore Fibers (MCF). Several fibers were characterized in terms of propagation delay, chromatic dispersion (CD) and polarization mode dispersion (PMD). The results show that the differential delay between the cores depends on the position of the core in the fiber and varies with temperature.

Adolfo Cartaxo
Theoretical models for the inter-core crosstalk in weakly-coupled multi-core fibres: Deterministic vs. random fluctuation along time
A. V. T. Cartaxo, J. L. Rebola, and T. M. F. Alves
Instituto de Telecomunicações, Lisboa, Portugal
Department of Information Science and Technology, ISCTE - Instituto Universitário de Lisboa, Portugal
We discuss theoretical models and their limitations for the characterization of inter-core crosstalk (ICXT) in weakly-coupled multi-core fiber systems. Models based on deterministic and random fluctuation of the ICXT over time are analyzed.

Jaume Comellas
Using spatial division multiplexing to avoid fragmentation in flex-grid optical networks
J. Comellas, J. Perelló, J. Solé-Pareta, and G. Junyent
Optical Communications Group (GCO), Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
Spectrum fragmentation is one of the main drawbacks of Gridless Optical Networks, and it becomes especially harmful under dynamic traffic conditions. When evolving from single fiber networks to spatial division multiplexed (SDM) ones, where many parallel cores/fibers are deployed, spectrum fragmentation still limits the network performance. In this work, the total available spectrum is partitioned according to the SDM dimension, and each one of the resulting partitions is assigned to each type of connections. This strategy is proposed as a simple method to eliminate spectrum fragmentation. By allocating all the same sized connections on the same spectral/spatial partition, the randomness in the size of the spectral voids left when connections finish is eliminated. The proposal is numerically evaluated using different network topologies and diverse traffic profiles. The obtained results show that spatial partitioning is an interesting solution for spectrum fragmentation avoidance in these scenarios.

Alessio Ferrari
Networking merit of spatial-division and band-division multiplexing: A statistical assessment
A. Ferrari, E. Virgillito, and V. Curri
Politecnico di Torino, Italy
We compare the networking merit of multiple bands – U-to-O band – by exploiting the installed cables (BDM) vs. multiple parallel fibers (SDM). Despite the better transmission performance, SDM only enables 15% more traffic than BDM on the German network and the European network for cardinality up to 5.
Keywords: transparent optical networks, multi-band transmission, SDM, physical layer aware networking.

Saurabh Jain
High density multicore SDM amplifiers
S. Jain¹, M. Wada², K. Shibahara², Y. Jung¹, I. A. Davidson¹, P. Barua¹, J. R. Hayes¹, T. Sakamoto², T. Mizuno², Y. Miyamoto², Y. Sasaki², K. Saitoh², K. Nakajima², and D. J. Richardson^1
1Optoelectronics Research Centre, University of Southampton, UK
²NTT Access Network Service Systems Laboratories, NTT Corporation, Japan
Multicore SDM amplifiers with high spatial multiplicity of 32 and 42 have been developed with single mode and few mode cores, respectively. The potential benefits of SDM amplifiers over as many conventional EDFAs will be discussed.

Ruben Luís
SDM network node architecture for higher than 1 petabit per second optical networks
R. S. Luis¹, B. J. Puttnam¹, G. Rademacher¹, T. A. Eriksson¹, Y. Hirota¹, S. Shinada¹, A. Ross-Adams², S. Gross², M. Withford², R. Maruyama³, K. Aikawa³, Y. Awaji¹, H. Furukawa¹, and N. Wada^1
1National Institute of Information and Communications Technology, Tokyo, Japan
²MQ Photonics Research Centre, Dep. of Physics and Astronomy, Macquarie Univ., NSW, Australia
³Fujikura Optical Technologies R&D Center, Fujikura Ltd., Chiba, Japan
In this work we revise recent contributions towards the demonstration of high capacity network nodes for spatial division multiplexing networks. We evaluate the evaluate the performance impact of spatial bypass for long distance transmission and address practical implementation aspects, such as multiplex section protection. We also address the impact of skew between spatial channels, particularly directed towards the use of homogeneous multicore fiber networks.

Jordi Perelló
Evaluation of add/drop flexibility requirements in future SDM-enabled ROADMs
J. Perelló¹, J. M. Gené¹, M. Klinkowski², J. Comellas¹, and S. Spadaro^1
1Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
²National Institute of Telecommunications, Warsaw, Poland
In this paper, we introduce five different architectures, with different degrees of flexibility, for implementing the local Add/Drop module of future Spatial Division Multiplexing (SDM)-enabled Re- configurable Optical Add & Drop Multiplexers (ROADMs), from a completely static transponder to spatial channel assignment to a fully- flexible transceiver to fiber and spatial channel assignment. The performance of the proposed architectures is evaluated and compared in a single SDM-enabled ROADM scenario, where local as well as bypass traffic is injected, supported by spectral super-channels at diverse bit-rates and employing different modulation formats. The obtained results illustrate the additional benefits attainable by those more flexible local Add/Drop architectures, at expenses of their increased hardware complexity.

Masatoshi Suzuki
Ultra-high capacity optical transmission over 10 Pbit/s based on optical space division multiplexing technologies
M. Suzuki, D. Soma, T. Tsuritani, and I. Morita
KDDI Research, Inc., Saitama, Japan
Recent progress on ultra-high capacity, space division multiplexed optical transmission is reviewed. The highest capacity of 10.16 Pbit/s has been achieved by using 19-core 6-mode fiber, and the highest capacity of 402.7 Tbit/s for multimode single core fiber has been demonstrated by using weakly-coupled 10-mode fiber with a standard cladding diameter.
Keywords: multi-core fiber, few mode fiber, space division multiplexing.

Jarosław Turkiewicz
Speciality fibre in high speed transmission application
J. P. Turkiewicz, Institute of Telecommunications, Faculty of Electronics and Information Technology, Warsaw University of Technology, Poland
In this paper we report on the high speed transmission with the SDM fibre dedicated for the data communication short transmission links.

Naoya Wada
Demonstrations of huge capacity space division multiplexing (SDM) transmission
N. Wada, B. Puttnam, G. Rademacher, R. S. Luis, Y. Awaji, and H. Furukawa
NTT Access Network Service Systems Laboratories, NTT Corporation, Japan
We demonstrate recent progress on huge capacity space division multiplexing (SDM) transmission technologies. Over 10 Peta bit/s SDM transmission using 38-core 3-mode fiber, over 0.6 Peta bit/s SDM transmission using 125 µm standard diameter 4-core fiber and related technologies are presented.

Krzysztof Walkowiak
An algorithm for provisioning of time-varying traffic in translucent SDM elastic optical networks
A. Włodarczyk, P. Lechowicz, D. Szostak, and K. Walkowiak
Wroclaw University of Science and Technology, Poland
We focus on the problem of resource allocation for time-varying traffic in translucent space- division multiplexing (SDM) elastic optical networks (EON) with back-to-back (B2B) signal regeneration. The performance is measured in terms of acceptable bandwidth blocking probability, usage of spectral resource (i.e. minimizing allocated bandwidth overhead compared to required traffic) and number of lightpaths' reallocations. We formulate and evaluate an effective algorithm for time-varying traffic allocation. Simulations are run on a representative network topology with time-varying traffic based on several types of network services with different underlying stochastic processes in order to properly project the real changes in time of the Internet traffic.

Shuangyi Yan
Routing and switching for multi-core fibre based multi-dimensional optical networks
Shuangyi Yan, Lida Liu, and Ruizhi Yang
High Performance Networks group, University of Bristol, UK
Multiple core fibres (MCFs) have been regarding as a potential technology to increase total fibre bandwidths. The recent developments of Multi-core fiber amplifier further leverage the feasibility of deploying MCFs in practical optical networks. However, there are still many challenges to route and switch optical signals efficiently in multi-dimensional optical networks. In this paper, a SDM/WDM ROADM is proposed and implemented with low port-count WSSs. Fibre-core bypassing is introduced to reduce the number of and port-count of WSSs in the implementation. The design requires less hardware without compromising on network performance with the developed routing core and wavelength assignment algorithm. We also evaluate several scenarios to deploy MCFs for Metro networks.

 

SWP invited presentations:

Carlos Alonso-Ramos
Harnessing subwavelength nanostructuration to control the propagation of light and sound in silicon waveguides
T. T. D. Dinh¹, J. Zhang¹, D. Oser¹, X. Le Roux¹, M. Montesinos¹, C. Lafforgue^1,2, F. Mazeas², D. Pérez-Galacho⁴, D. Benedikovic¹, E. Durán-Valdeiglesias¹, V. Vakarin¹, O. Ortiz¹, A. Rodirguez¹, O. Alibart², P. Cheben⁵, S. Tanzilli², L. Labonté², D. Marris-Morini¹, E. Cassan¹, D. Kimura¹, L. Vivien¹, and C. Alonso-Ramos^1
1Universite Paris-Saclay, Univ. Paris-Sud, CNRS, Centre de Nanosciences et de Nanotechnologies, Palaiseau, France
²École Normale Supérieure Paris-Saclay, Université Paris-Saclay, Cachan, France
³Université Côte d’Azur, CNRS, Institut de Physique de Nice, France
⁴ITEAM Research Institute, Universitat Politècnica de València, Spain
⁵National Research Council, Ottawa, Canada
Periodically patterning silicon with a pitch sufficiently small to suppress diffraction effects opens new degrees of freedom to control light propagation in silicon photonic circuits with unprecedented flexibility. Indeed, this subwavelength metamaterial concept has enabled the demonstration of several Si photonic components, some with the best performance ever reported. On the other hand, near-infrared photons and GHz phonons in nanoscale Si waveguides have comparable wavelengths (around 1 μm). Thus, subwavelength nanostructuration of silicon has a great potential to shape the properties (confinement, dispersion, etc.) of both, photonic and phononic modes, thereby opening new routes to engineer light-sound interactions in silicon, e.g. Brillouin scattering. Here, we present our most recent results on the subwavelength engineering of silicon for the implementation of high-performance photonic and optomechanical components.

Francesco Baldini
Biosensing with optical fibres: Past, present and future
F. Baldini, IFAC-CNR, Chemical and Biochemical Optical Sensor Group, Sesto Fiorentino (Firenze), Italy

Tiziana Bond
Fiber enabled optical sensors for biochem detection
T. Bond¹, A. Chang¹, S. Harrison¹, B. Bauman¹, S. Gilmore¹, K. Heinz¹, G. Nunzi-Conti², L. Echeveria³, and P. Singh^4
1Lawrence Livermore National Laboratory, CA, USA
²IFAC-CNR, Institute of Applied Physics “N. Carrara”, Sesto Fiorentino, Italy
³University of California San Diego, La Jolla, CA
⁴University of California Davis, CA, USA
Our overarching goal aims at developing portable solutions for biohazards protection, biodegradation remediation, as well as continuous, in-situ chemical surveillance of health of systems and environments. We will present our current research on fiber based optical sensor for miniaturized, in-situ and real-time chemical spectroscopy, including IR, Raman, and plasmonics. Specifically, we intend to review an all-optical robust gas cell, small as the palm of a hand, prototyped and fielded for pollutant gas sensing down to ppm level, an optical resonators for recognition of biological surrogates, with the potential of striking form factor reduction, and customized fiber probes for enhanced Raman designed and used for mixed chemical samples detection.

Muriel Botey
Towards a feasible non-Hermitian light management
M. Botey¹, W. W. Ahmed², Y. Wu², R. Herrero¹, and K. Staliunas^1,3
1Departament de Física, Universitat Politècnica de Catalunya (UPC), Terrassa, Barcelona, Catalonia
²Division of Computer, Electrical and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
³Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Catalonia
The recent focus on Non-Hermitian systems originates from the novel physical phenomena owing to the interplay between gain and loss. Such systems may break the spatial symmetry and allow to arbitrarily control the flow of light. The approach is based on a modification of the classical Hilbert transform to design Non-Hermitian systems on demand, with desired shapes and topologies, restricting the dimensionality of the complex index parameter space, keeping the physical properties within practical limits and realizable with a finite collection of materials.
Keywords: non-Hermitian optics, PT-symmetry, metamaterials.

Manish Chauhan
Metabolite identification of helicobacter pylori supernatant using near-IR Raman spectroscopy
M. Chauhan¹, A. Buckley², A. Jha³, M. Wilcox², V. Subramaniam⁴, and P. Valdastri^1
1School of Electronics and Electrical Engineering, University of Leeds, UK
²School of Medicine, University of Leeds, UK
³School of Chemical and Process Engineering, University of Leeds, UK
⁴Faculty of Medicine and Health University of Leeds, University of Leeds, UK
Helicobacter pylori, a non-invasive gram-negative bacteria is well known for its direct cause and effect relationship with peptic ulcer, gastric or duodenal ulceration. Its severe effect on human begin with its colonization and production of various enzyme like Vacuolating cytotoxin, Urease and Heat shock proteins. Urease is complex spherical protein which causes hydrolysis of gastric urea to ammonia and CO2. The enzymatic reaction results in increase of gastric pH and hence results in gastric cancer. We present a photonic based technique to identify these proteins in its natural supernatant condition. The Raman spectrum of Helicobacter pylori is reported and the vibrational peaks are identified with corresponding chemical bonds in the biochemical enzyme. This can lay the foundation for future diagnostic tool for clinical detection of peptic ulcer, gastric or duodenal ulceration.
Keywords: helicobacter pylori, urease, Raman spectroscopy, VacA, CagA.

Gabriella Cincotti
Investigation of bacterial interactions using lab on chips
L. Nichele¹, A. De Ninno², A. Gerardino², F. R. Bertani², D. Visaggio³, M. Lucidi¹, P. Visca², L. Businaro², and G. Cincotti^1
1Engineering Department, University Roma Tre, Italy
²CNR Institute for Photonics and Nanotechnologies, Rome, Italy
³Department of Sciences, University Roma Tre, Italy
Staphylococcus aureus is one of the most common bacteria that infect the lungs of cystic fibrosis (CF) patients, during the first decade of their life. Pseudomonas aeruginosa becomes the prevalent pathogen in the second and third decades of their lives and it is recognized as the leading cause of lung function decline. It is known that the growth of S. aureus is inhibited by anti-staphylococcal compounds produced by P. aeruginosa, but the impact of the S. aureus presence in the course of CF disease is still under debate. Better understanding of the mechanisms driving the succession of bacterial populations in the lung of CF patients is fundamental to define a relationship between microbiological characteristics, disease status and treatment response. We have designed and fabricated two different lab-on-chip devices to investigate the antagonistic interactions of S. aureus and P. aeruginosa. Microfluidic devices have become useful tools for medical, biochemical and microbiological investigations, and nowadays they have the potential to increase the efficiency of conventional analysis like those involved in drug discovery, preclinical tests and clinical trial processes. Our devices have been fabricated in polydimethylsiloxane (PDMS), that shows a satisfactory thermal stability, gas permeability and a low glass transition temperature, that allows a good flexibility at room temperature. The first lab-on-chip device is composed of three parallel compartments, that are filled by bacteria, interacting by a series of hundreds microchannels; a cell trap is inserted at the center of each microchannel, to prevent the contact between different bacterial species. A physical agarose barrier replaces the cell traps in the second microfluidic layout, to prevent that the bacteria enter in contact within the microchannels. We use fluorescent-tagged bacteria and we monitor their growth rate inside the microchannels, using confocal microscopy and automatic cell counting software.

Crina Cojocaru
Harmonic generation in the opaque region of semiconductors: The role of the surface and magnetic nonlinearities
C. Cojocaru¹, L. Rodriguez Sune¹, M. Scalora², and J. Trull^1
1Universitat Politècnica de Catalunya, Physics Department, Terrassa, Barcelona, Spain
²Charles M. Bowden Research Center, AMRDEC, RDECOM, Redstone Arsenal, AL, USA
The use of semiconductors in the process of fabrication of actual nano devices such as GaAs, GaP or Si is at the front edge of nowadays technology, exploiting the properties of light propagation and localization at nanometric scale in new and surprising ways. At these scales the usual theory describing the nonlinear (NL) effects of electromagnetic fields should be revisited and analyzed. Recently we have studied in detail the generation of the SH and TH in the opaque region of semiconductors as GaAs or Si, going beyond the previous studies and we study deeply the nonlinear process in order to infer which are the different mechanisms leading to the PL SH generation. We demonstrate that the bulk nonlinearity is not the only one active term and that we have strong contributions coming from the surface and magnetic Lorentz terms, which usually are either hidden by the bulk contributions or assumed to be negligible. Experimental and theoretical simulations are contrasted, using a hydrodynamic model [1,2] that accounts for all salient aspects of the dynamics, including surface and bulk generated harmonic components. [3] Here we extend this study to other semiconductors as Si and GaP. We also consider resonant structures as gratings and nanowires where the nonlinear effect is enhanced. Although the harmonic generation in this regime and materials has a very low efficiency, these findings have significant repercussions and are consequential in nanoscale systems, which are usually investigated using only dispersionless bulk nonlinearities, with near-complete disregard of surface and magnetic contributions and their microscopic origins.
[1] V. Roppo, M. Centini, C. Sibilia, M. Bertolotti, D. de Ceglia, M. Scalora, N. Akozbek, M. J. Bloemer, J. W. Haus, O. G. Kosareva, and V. P. Kandidov, Phys. Rev. A 76, 033829, 2007.
[2] M. Scalora, M. A. Vincenti, D. de Ceglia, V. Roppo, M. Centini, N. Akozbek, and M. J. Bloemer Second- and third-harmonic generation in metal-based structures, Phys.Rev. A 82, 043828 (2010).
[3] L. Rodriguez Sune, J. Trull, M. Scalora and C. Cojocaru “Harmonic generation in the opaque region of GaAs: the role of the surface and magnetic nonlinearities”, Optics Express 27, no. 8, 26120 (2019).

Stelios Couris
UV laser photo-reduction of graphene oxide and graphene fluoride for the efficient tuning of their nonlinear optical response
I. Papadakis^1,2, A. Stathis^1,2, N. Karampitsos^1,2, M. Stavrou^1,2, D. Kyrginas^1,2, and S. Couris^1,2
1Department of Physics, University of Patras, Greece
²Institute of Chemical Engineering Sciences (ICE-HT), Foundation for Research and Technology-Hellas (FORTH), Patras, Greece
In the present work, some recent results are presented concerning the use of UV laser reduction of fluorinated graphene and graphene oxide in order to modify their optical and nonlinear optical properties in a controlled way. The photo-reduction was achieved using 355 nm UV light from a 4 ns Nd:YAG laser, while the NLO properties of the derivatives were studied by means of the Z-scan technique, employing 4 ns, visible (532 nm) laser excitation. It is shown that the modification of the degree of oxidation/fluorination of the two graphene derivatives, can greatly alter their optical and their nonlinear optical response. The present results demonstrate the efficiency of the reduction by UV laser light, for the efficient modulation and tuning of the nonlinear response of graphene oxide and fluorinated graphene in view of specific applications in photonics and optoelectronics.
Keywords: graphene oxide, fluorographene, photo-reduction, nonlinear optics, Z-scan.

Cid de Araújo
Nonlinear parametric processes and random lasing in ensembles of crystalline nanocrystals
C. B. de Araújo, Departamento de Física, Universidade Federal de Pernambuco, Recife, PE, Brazil
The multiple scattering of light propagating inside disordered media allows observation of phenomena such as enhanced absorption of incident photons, collective scattering, parametric nonlinear effects, and random lasing. In this communication, I will highlight our recent experiments with ensembles of nanocrystals that illustrate selected phenomena in scattering media and possible applications. The generation of incoherent second harmonic (hyper-Rayleigh scattering) in powders of NaNbO₃ nanocrystals, optical parametric amplification in β-BaB₂O₄ nanocrystals, and random lasing in YAl₃(BO₃)₄ nanocrystals doped with rare-earth ions, will be discussed to exemplify the use of nonlinear nanocrystals in disordered photonics.

Domenico de Ceglia
Thermal tuning of resonant gratings using a phase-change material
M. F. Kashif¹, A. D’Orazio¹, M. Grande¹, T. Stomeo², M. De Vittorio^2,3, M. A. Vincenti^4,5, I. Vassalini^4,5,6, I. Alessandri^4,5, C. De Angelis^4,5, and D. de Ceglia^7,5
1Dipartimento di Ingegneria Elettrica e dell’Informazione, Politecnico di Bari, Italy
²Center for Bio-Molecular Nanotechnology, Istituto Italiano di Tecnologia (IIT), Italy
³Dipartimento di Ingegneria dell’Innovazione, Università del Salento, Italy
⁴Dipartimento di Ingegneria dell’Informazione, University of Brescia, Italy
⁵National Institute of Optics (INO), Italy
⁶Dipartimento di Ingegneria Meccanica e Industriale, University of Brescia, Italy
⁷Dipartimento di Ingegneria dell’Informazione, University of Padova, Italy
We show a new path to endow the optical response of resonant gratings with tunability. Modulation of reflectance in response to a thermal stimulus is demonstrated in an array of pillars grown on top of a grounded, high-index slab. This photonic structure may host a variety of resonances that can be tuned across infrared and visible ranges, namely guided-mode resonances, Mie resonances, plasmonic resonances and Fabry-Pérot resonances. When the structure is spin-coated with a nanofilm of vanadium-dioxide – a phase change material that switches from an insulator to a metal phase at 68°C – we experimentally observe reflectance changes on the order of 10% near the resonances in the visible, and find good agreement with predictions based on numerical simulations. We present design strategies to improve the tunability in the visible range and to extend it in other portions of the spectrum.

Massimo De Vittorio
Advanced optoelectronic devices for neuroscience
M. Pisanello¹, B. Spagnolo¹, L. Sileo¹, F. Pisano¹, A. Balena^1,2, F. Pisanello¹, and M. De Vittorio^1,2
1Istituto Italiano di Tecnologia, CBN, Lecce, Italy
²Dipartimento di Ingegneria dell’Innovazione, Università del Salento, Lecce, Italy
Advances in optogenetics and optical imaging techniques have progressively changed the approach used to record functional signals related to neural activity. Besides standard electrophysiology techniques, in the last 20 years the use of light sensitive molecular tools for triggering and monitoring brain functions increased the demand for the development of novel optoelectronic devices for light delivery, light collection, and electrical recording from the living brain. This goal can be achieved by combining different devices or integrating both optical and electrical elements on the same implantable probe. Here we review the latest advancements in this field with particular emphasis on fiber-based optrodes and non-planar manufacturing techniques.
Keywords: optrodes, optical fibers, optogenetics, neuroscience.

Beata Derkowska-Zielińska
Heterocyclic azo dyes as a new family of photochromic materials
B. Derkowska-Zielinska¹ and O. Krupka^2
1Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Toruń, Poland
²Taras Shevchenko National University of Kyiv, Ukraine
The photo-physical properties of novel heterocyclic azo dyes thin films dispersed in PMMA matrix as well as incorporated as side groups of a side-chain polymer were studied. It was found that the optical properties of heterocyclic azo dyes are very interesting and are strongly depend on different substituents in the phenyl ring. The obtained results allowed to draw conclusions about their potential use in photonics and optoelectronics.
Keywords: azo dyes, thin films, optical properties.
[1] B. Derkowska-Zielinska, L. Skowronski, T. Kozlowski, V. Smokal, A. Kysil, A. Biitseva, O. Krupka: Influence of peripheral substituents on optical properties of heterocyclic azo dyes, Optical Materials, vol. 49, pp. 325-329, 2015.
[2] B. Derkowska-Zielinska, L. Skowronski, A. Biitseva, A. Grabowski, M. K. Naparty, V. Smokal, A. Kysil, O. Krupka: Optical characterization of new heterocyclic azo dyes containing polymers thin films, Applied Surface Science, vol. 421, pp. 361-366, 2017.
[3] B. Derkowska-Zielinska, K. Matczyszyn, M. Dudek, M. Samoc, R. Czaplicki, A. Kaczmarek-Kedziera, V. Smokal, A. Biitseva, O. Krupka: All-optical poling and two-photon absorption in heterocyclic azo dyes with different side groups, Journal of Physical Chemistry C, vol. 123, pp. 725-734, 2019.
[4] B. Derkowska-Zielinska, D. Szmigiel, A. Kysil, O. Krupka, A. Kozanecka-Szmigiel: Photoresponsive behavior of heterocyclic azo polymers with various functional groups, Journal of Physical Chemistry C, vol. 124, pp. 939-944, 2020.

Jean-Luc Duvail
Optical properties of advanced gold-based nanowires and exploitation as plasmon mediated remote Raman sensor
D. Funes-Hernando¹, M. Peláez-Fernández², D. Winterauer³, J.-Y. Mevellec¹, R. Arenal^2,4, T. Batten³, B. Humbert¹, M. Bayle¹, and J.-L. Duvail^1
1Institut des Matériaux Jean Rouxel (IMN), UMR 6502 CNRS and Université de Nantes, France
²Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragon, Universidad de Zaragoza, Spain
³Renishaw plc, New Mills, Wotton-under-Edge, UK
⁴ARAID Foundation, Zaragoza, Spain
The propagative nature of surface plasmon polaritons (SPP) and the strong local field enhancement can both be promoted in plasmonic nanowires. Their exploitation into building blocks for plasmonic based devices is a promising target for nano-sensors. Here, the proof-of-concept of a SPP-mediated remote Raman effect is reported. Remote Raman spectroscopy consists in the separation by many micrometres of the excitation laser spot on one tip of the nanowire, and the Raman detection at the opposite tip. Coaxial nanowires have been specially designed for this achievement, with a gold core to propagate SPP and a Raman-emitting shell of poly(3,4-ethylene-dioxythiophene) (PEDOT) [1]. However, the weakness of the Raman signal is a drawback for efficient sensors. It is proposed to enhance the overall signal by improving the in-coupling of the focused laser (1 µm diameter, typically) with the nanowire and the out-coupling of the plasmon-mediated signal at the remote location. Dry laser heating treatments were used to enlarge the gold nanowire tips with to obtain dog-bones like nanowires. A micro-Rayleigh scattering study has confirmed that the excrescence located at one or at the two tips of the nanowires provides an enhanced in and out coupling. The plasmonic properties of these original nanowires have been determined by an EELS-STEM study.
[1] D. Funes-Hernando, M. Peláez-Fernández, D. Winterauer, J.-Y. Mevellec, R. Arenal, T. Batten, B. Humbert, and J .L. Duvail, Nanoscale (2018) 10, 6437-6444.

Abdelkrim El Ghayoury
Thiophene-based molecular materials for nonlinear optics
A. El-Ghayoury¹, Y. Cheret¹, A. Popczyk^1,2, A. Ayadi^1,3, A. Szukalski², J. Mysliwiec², and B. Sahraoui^1
1MOLTECH-Anjou, UMR 6200, CNRS, UNIV Angers, France
²Faculty of Chemistry, Wroclaw University of Science and Technology, Poland
³Laboratoire de Physico-chimie de l’état solide, Département de Chimie, Faculté des sciences de Sfax, Université de Sfax, Tunisia
In this paper, we describe the synthesis of a thiophene-based donor-π-acceptor system, namely (E)-2-(4-nitrostyryl)-5-phenylthiophene (Th-CN₂), which was prepared under basic conditions as previously described in the literature. This thiophene based -conjugated system was mixed with poly(methyl methacrylate) (PMMA) and the resulting thin film was subjected to nonlinear optical investigations by means of both second and third harmonic generation. The obtained nonlinear optical responses have been compared with the previously prepared π-conjugated systems as well as with a silica and quartz reference compounds. Although the obtained nonlinear optical response is low, such thiophene-based π-conjugated systems are valuable materials for photonic applications.
Keywords: phenylthiophene, π-conjugated system, UV-visible absorption, nonlinear optics, SHG, THG.

Didier Felbacq
A single layer representation for the field diffracted by several scatterers
A. Gourdin¹, P. Genevet², and D. Felbacq^3
1Safran Electronics and Defense, Paris, France
²CRHEA CNRS, Sophia-Antipolis, France
³L2C-CNRS, Univ. Montpellier, France
The modeling and design of new optical devices such as metasurfaces or metamaterials required the solving of Maxwell equations in the presence of many scatterers. While there are efficient algorithms such as the Fast Multipole Method, they generally rely on a representation of the field by computationally complicated functions, i.e. multipoles. In the present work, we propose the use of a single layer representation of the field allowing to involve monopoles only, thus leading to a much simpler and efficient algorithm.

Joaquin Fernandez
A simple model for dye based solid-state random lasers
J. Fernandez¹, I. Iparraguirre², J. Azkargorta², S. Garcia-Revilla², and R. Balda^2,3
1Donostia International Physics Center DIPC, San Sebastián, Spain
²Dpto. de Física Aplicada I, Escuela de Ingeniería de Bilbao, Universidad del País Vasco UPV/EHU, Bilbao, Spain
³Materials Physics Center CSIC-UPV/EHU, San Sebastián, Spain
Random laser efficiency of dye-based solid-state materials is investigated by using a picosecond pumping regime. The measured laser output is found to be dependent on the integration time employed. For a long time integration, the whole signal, spontaneous and stimulated, is recovered and there is no detectable threshold due to the very high quantum yield of the dyes. However, for a short time integration, only the stimulated emission is detected and a threshold and a curvature in the input/output diagram are observed. The authors have applied to these random lasers (RLs) a previously developed model, which satisfactorily describes the RL behavior of inorganic Nd3+ doped powders. The model uses a distribution of photon paths with different lengths, instead of a single average path length, as well as, a sharing of population inversion among the different photon paths. From the model results it can be concluded that, from an energetic point of view, solid state dye RLs behave quite similarly to Nd-doped stoichiometric powder crystal materials.

Stavroula Foteinopoulou
Pushing EM enhancement beyond the sub-wavelength scale: A paradigm based on ultra-slow light
S. Foteinopoulou, Electrical and Computer Engineering Dept., Univ. of New Mexico, Albuquerque, USA
In passive systems, electromagnetic (EM) field enhancement is typically accomplished by a spatial “squeezing” effect, where a wide input beam converts to a spatially-confined mode by utilizing localized resonances (although non-resonant mechanisms have also been reported). Hence, EM enhancement is inherently a sub-wavelength phenomenon: higher enhancement requires deeper-subwavelength mode confinement. Here we utilize ultra-slow-light waveguides to achieve EM enhancement by means of accumulating EM energy within a specific region over large time intervals with no significant spatial squeezing effect. We discuss the dynamics of the spatial extent of the enhanced EM energy. Our results show that EM enhancement can cover areas corresponding to several free-space wavelengths which can be important in the advancement of active photonic devices.

Konstantin Gaikovich
Theory and experiments in near-field subsurface diagnostics
K. P. Gaikovich, Institute for Physics of Microstructures RAS, Nizhny Novgorod, Russia
Theoretical and experimental results in the study of methods of near-field subsurface sounding based on the solution of inverse scattering problems are presented in application to diagnostics of dielectric inhomogeneities and targets with nonlinear susceptibility, retrieval of the subsurface dielectric structure in frequency dispersive and strongly absorbing living tissues. These methods of subsurface tomography, holography and profiling demonstrate the possibility to realize a subwavelength resolution in non-destructive testing and biomedical diagnostics.

Ambra Giannetti
A fluorescence-based POCT device for immunosuppressant-drug monitoring in transplanted patients
A. Giannetti¹, F. Baldini¹, C. Berrettoni¹, S. Tombelli¹, C. Trono¹, G. Porro², R. Bernini³, I. A. Grimaldi³, G. Testa³, G. Persichetti³, C. Gärtner⁴, H. Becker⁴, M. Berner⁵, M. Schubert⁵, M. T. O’Connell⁶, D. Carney⁶, G. Orellana⁷, A. B. Descalzo⁷, F. Salis⁷, P. Freitas⁸, P. Luppa⁹, H. Bittersohl⁹, G. Gauglitz¹⁰, U. Hilbig¹⁰, and K. Freudenberger^10
1Istituto di Fisica Applicata “Nello Carrara”, Consiglio Nazionale delle Ricerche (IFAC-CNR), Sesto Fiorentino, Firenze, Italy
²Datamed S.r.L., Rodano, Italy
³Institute for Electromagnetic Sensing of the Environment, CNR, Napoli, Italy
⁴Microfluidic ChipShop GmbH, Jena, Germany
⁵Institute for Photovoltaics, University of Stuttgart, Stuttgart, Germany
⁶Probe Scientific Limited, Thurleigh, Bedfordshire, UK
⁷Chemical Optosensors and Applied Photochemistry Group, Department of Organic Chemistry, Faculty of Chemistry, Complutense University of Madrid, Spain
⁸INESC-MN, Lisbon, Portugal
⁹Institut für Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar der TU München, Germany
¹⁰Institute of Physical and Theoretical Chemistry, Eberhard Karls Universität, Tübingen, Germany
Therapeutic drug monitoring plays an important role in transplanted patient treatment by enabling the assessment of the correct dosage of drugs characterized by a narrow therapeutic window. Since only protein-unbound (free) drugs can cross membranes and bind to receptors to produce the required pharmacological effect, free drug concentrations are more closely related to efficacy and also to toxicity. At this aim, a novel point of care testing (POCT) optical device for the detection of blood immunosuppressant free fraction in transplanted patients was designed and tested, with the body interface constituted by an intravascular microdialysis catheter (MicroEye®), which provides the dialysate as clinical sample. The work was undertaken in the framework of the EU project NANODEM (NANOphotonic DEvice for Multiple therapeutic drug monitoring). The benefit of this device will be an optimized dosage of the therapeutic drugs to support patient management in a clinical environment. Calibration curves for cyclosporine A (CyA) and mycophenolic acid (MPA) in dialysis perfusate (20% Lipofundin) were obtained with limit of detection for CyA and MPA of 0.48 ng/mL and 0.79 ng/mL, respectively. In addition, real clinical Lipofundin-based microdialysate samples, each containing CyA and MPA, were tested and results were compared with a novel liquid chromatography–tandem mass spectrometry (LC-MS/MS) method that was developed within the course of the NANODEM project at the Institute of Clinical Chemistry and Pathobiochemistry, Klinikum rechts der Isar der TU München.

Marco Grande
Plasmonic nanostructures on curved surfaces for fiber-based sensors
M. F. Kashif¹, F. Pisano², A. Balena^2,3, M. Pisanello², T. Stomeo², F. Pisanello², M. De Vittorio^2,3, A. D’Orazio¹, and M. Grande^1
1Dipartimento di Ingegneria Elettrica e dell’Informazione, Politecnico di Bari, Italy
²Fondazione Istituto Italiano di Tecnologia, Center for Biomolecular Nanotechnologies, Arnesano , Italy
³Dipartimento di Ingegneria Dell’Innovazione, Università del Salento, Lecce, Italy
Plasmonic devices on a curved surface can open exciting new possibilities for guiding, focusing, deflecting the propagation of plasmonic waves and controlling plasmonic resonances [1]. In particular, plasmonic nanostructures can be exploited to realize optical fiber-based plasmonic devices, such as advanced optical probes for biological sensing applications [2], even though their fabrication on curved substrates is quite challenging [3]. In this talk, we will discuss the perspectives and challenges that lie in the design and fabrication of plasmonic devices with a special focus on curvature induced effects and implications. We will also present results regarding a fiber-based sensor constituted by gold nano-gratings built on a curved surface.
[1] D. Singh, A. Libster-Hershko, R. Shiloh and Ady Arie, “Curved space plasmonic optical elements,” Optic Letters 44(21), 5234-5237 (2019).
[2] P. Vaiano, B. Carotenuto, M. Pisco, et al., “Lab on fiber technology for biological sensing applications,” Laser Photonics, 10(6), 922-961 (2016).
[3] S. Aksu, M. Huang, A. Artar, et al., “Flexible plasmonics on unconventional and nonplanar substrates,” Adv. Mater. 23(38), 4422–4430 (2011).

Tatjana Gric
Investigation of nonlocal hyperbolic metamaterials
T. Gric^1,2,3 and E. U. Rafailov^1
1Aston Institute of Photonic Technologies, Aston University, Birmingham, UK
²Department of Electronic Systems, Vilnius Gediminas Technical University, Vilnius, Lithuania
³Semiconductor Physics Institute, Center for Physical Sciences and Technology, Vilnius, Lithuania
Composites designed by employing metal/dielectric composites coupled to the components of the incident electromagnetic (EM) fields are named metamaterials (MMs), and they display features not observed in nature. This type of artificial media has attracted great interest, resulting in ground-breaking theory that bridges the gap between EM and photonic phenomena. Practical applications of MMs have been delayed due to the high losses related to the use of metallic composites, on top of the challenges in manufacturing nanoscale, three-dimensional structures. Novel materials – for instance, graphene or transparent-conducting oxides (TCOs), employed for the production of multi-layered MMs – can significantly suppress undesirable losses. It is worthwhile noting that three-layered nanocomposites enable an increase in the frequency range of the surface wave. This work analyzes recent progress in the physics of multi-layered MMs. We deliver an outline of key notions, such as effective medium approximation, and present multi-layered MMs based on the three-layered structure. An overview of graphene multi-layered MMs reveals their ability to support Ferrell-Berreman (FB) modes. We also describe the tunable properties of the multi-layered MMs.

Cristiana Grigorescu
Preparation and study of core shell Fe₃O₄/Au nanoparticles for traceability of blood vessels and biosensing by surface enhanced Raman spectroscopy
A.-M. Iordache¹, C. Rizea², C. Giuglea³, C. N. Zoita¹, I. Stamatin⁴, S. M. Iordache¹, C. R. Stefan (Iordanescu)¹, M. I. Rusu¹, L. Tortet⁵, A. Tonetto⁴, R. Notonier⁵, and C. E. A. Grigorescu
¹National Institute of Research and Development for Optoelectronics INOE 2000, Magurele, Romania
²ROXY VETERINARY S.R.L. Magurele, Romania
³University of Medicine and Pharmacy Carol Davila, Bucharest, Romania
⁴Faculty of Physics, University of Bucharest, Romania
⁵Aix-Marseille Universitè, MADIREL and Centrale Marseille, CNRS, Federation Sciences Chimiques Marseille – PRATIM, France
Fe₃O₄/Au core-shell nanoparticles have been prepared using reverse micelle synthesis with the aim of studying the traceability of blood vessels and allow biosensing through surface enhanced Raman spectroscopy. The shell provides protection against oxidation, plasmon properties and prevents aggregation of the magnetic nanoparticles. Structural and optical characterisation has been performed through XRD, SAXs, SEM-EDS, confocal microscopy, spectroscopic ellipsometry, DLS, and Raman spectroscopy. A solution of Fe₃O₄/Au core-shell nanoparticles in fluorescein has been injected into fresh ex-vivo animal tissues to check the traceability of blood vessels. Postbariatric surgery as well as rapid diagnosis on circulatory issues are examples of future applications.

Johannes Heitz
Laser-induced periodic surface structures (LIPSS) for biomedical and sensing applications
J. Heitz¹, M. Muck¹, J. Vujovic¹, W. Baumgartner², A. W. Hassel³, S. A. Lone³, B. Steinhauser¹, C. Hrelescu¹, T. A. Klar¹, G. Buchberger¹, A. Weth², and D. Baiko^2
1Institute of Applied Physics, Johannes Kepler University Linz, Austria
²Institute of Biomedical Mechatronics, Johannes Kepler University Linz, Austria
³Institute of Chemical Technology of Inorganic Materials, Johannes Kepler University Linz, Austria
The interference of an incident laser beam with first order diffracted light running parallel to a surface can induce the formation of ripple structures with periodicities in the wavelength and sub-wavelength range of the irradiating light. These are spatially periodic structures, also denoted as laser-induced periodic surface structures (LIPSS). Ripple formation is a general phenomenon, observed practically always on solid or liquid surfaces after laser irradiation with polarized light within certain ranges of laser parameters. Medical implants consisting of Ti-alloys may have to be removed after several months or years and shall therefore not be completely overgrown by the cells after implantation. Suppression of cell growth at Ti-alloy surfaces could be achieved by 1040 nm fs laser-ablation creating self-organized sharp spikes with dimensions in the 10 μm-range which are superposed by a fine sub-μm LIPSS structure. Compared to flat surfaces, the cell density on the micro/nano-structured surfaces was significantly lower, the coverage was incomplete and the cells had a clearly different morphology. The best results regarding suppression of cell growth were obtained on structures which were additionally electrochemically anodized under acidic conditions [1]. The laser-processing as well as the anodization resulted in a (temporal) change of the water contact angle of the surfaces, which had however no direct influence on the cell growth. Localized-plasmon voltammetry (LPV) bears a great potential for electrochemical sensing applications. We demonstrated LPV on gold nanowires to optically monitor the pH dependent oxidation and reduction of the gold nanowires [2]. For production of the gold nanowires, a PET foil (thickness of 50 μm) with 248 nm KrF laser-induced LIPSS structures was used as the substrate. The gold nanowire array was produced by a 70° inclined evaporation of a 15 nm gold layer. Application of a potential to the nanowires leads to a shift of the plasmon resonance correlated to the pH.
Keywords: photonic micro- and nanostructures, laser-induced periodic surface structures, cell adhesion, gold nano-wires, plasmon resonances.
[1] J. Heitz, et al.: Femtosecond laser-induced microstructures on Ti substrates for reduced cell adhesion, Applied Physics A, vol. 123, pp. 734, 2017.
[2] B. Steinhauser, C. Vidal, R.-A. Barb, J. Heitz, A. I. Mardare, A. W. Hassel, C. Hrelescu, T. A. Klar: Localized-plasmon voltammetry to detect pH dependent gold oxidation, The Journal of Physical Chemistry, vol. 122, pp. 4565−4571, 2018.

Ramon Herrero
Stabilized bright narrow beams from edge-emitting lasers
J. Medina¹, R. Herrero¹, M. Botey¹, and K. Staliunas^1,2
1Departament de Física, Universitat Politècnica de Catalunya, Spain
‎²Institució Catalana de Reserca i Estudis Avançats (ICREA), Spain
We present new edge-emitting laser configurations to improve the laser performance with a double benefit, light localization into a bright narrow beam emission and the suppression of spatiotemporal dynamics. The proposal is based on the management of the transverse light flow inside the laser cavity through non-Hermitian potentials. We impose pump and refractive index modulations to generate a local PT-symmetric configuration with a central symmetry axis. Such configuration induces the accumulation in axis of light generated in the whole active layer. The exploration of the modulation parameters shows a significant improvement of the intensity concentration, stability and brightness of the emitted beam.

Mikko Huttunen
Non-local field effects in nonlinear plasmonic metasurfaces
M. J. Huttunen¹, S. Bin-Alam², O. Reshef³, Y. Mamchur^2,4, T. Stolt¹, J.-M. Ménard³, K. Dolgaleva^2,3, R. W. Boyd^2,3,5, and M. Kauranen^1
1Photonics Laboratory, Physics Unit, Tampere University, Finland
²School of Electrical Engineering and Computer Science, University of Ottawa, Canada
³Department of Physics, University of Ottawa, Canada
⁴National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute,” Ukraine
⁵The Institute of Optics and Department of Physics and Astronomy, University of Rochester, New York, USA
Nonlinear optical processes play a key role in many fields of photonics ranging from multiphoton microscopy to ultrashort pulse generation. Recent progress in nanophotonics and metamaterials has created a growing demand for efficient and nanoscale nonlinear optical components. This demand is hard to answer by using traditional materials motivating the search for alternative approaches and materials. Nonlinear plasmonic metasurfaces have recently emerged as a potential solution for enabling efficient and nanoscale nonlinear optics. Despite steady progress, the so far achieved conversion efficiencies (10^-7–10^-10) have not yet rivalled conventional nonlinear materials. Here, we discuss our recent work to develop more efficient nonlinear plasmonic metamaterials. We focus on metasurfaces supporting collective responses known as surface lattice resonances, which are associated with remarkably narrow spectral features. Such narrow resonances are very promising also for nonlinear optics as they have been predicted to considerably boost nonlinear responses. We will also present our recent results to fabricate such metasurfaces, and discuss how multiply resonant metasurfaces could be realized.

Branislav Jelenković
Infrared detectors with natural biological structures
D. Grujić¹, D. Vasiljević¹, P. Atanasijević², P. Mihajlović², M. Simović-Pavlović¹, D. Pantelić¹, and B. Jelenković^1
1Institute of physics Belgrade, Serbia
²Faculty of Electrical Engineering, University of Belgrade, Serbia
We have shown that nanostructured biophotonic particles can be used as efficient detectors of infrared radiation. We used digital holographic method to construct an imaging infrared detector, measuring nano scale deformations induced by thermal heating of Morpho butterfly wing-scales. We explained mK sensitivity of the discovered principle with additional thermal effects on wing scales deformation produced by thermophoretic forces, i.e., forces acting on molecules trapped in a volume smaller then then their mean free path. We discuss how effect can be further amplified for better sensitivity and resolution, by suitable choices of materials for functionalizing wing scales. We will also discuss biomimetics based on observed wing’s structures, possible methods for their fabrications.

Boris Lembrikov
Four-wave mixing (FWM) in the optical waveguide with a smectic A liquid crystal (SALC) core layer
B. I. Lembrikov, D. Ianetz, and Y. Ben-Ezra
Department of Electrical Engineering, Holon Institute of Technology, Israel
Four-wave mixing (FWM) is the nonlinear optical process with four interacting electromagnetic waves [1]. It is a third-order process governed by the third-order nonlinear susceptibility and allowed in all media, both with the inversion symmetry or without it [1]. Liquid crystals (LCs) are promising candidates for applications in modern photonics, nonlinear optics and optical signal processing because they are characterized by large birefringence, easy susceptibility to external field perturbation, and large optical nonlinearity [2]. In particular, LC based optical waveguides can be implemented on a Si platform [2], [3]. Nematic LCs (NLCs) with the orientational long-range order have been mainly used and investigated theoretically and experimentally [2], [3]. However, smectic A LCs (SALCs) characterized by a positional long-range order can be used in nonlinear optical applications due to the low scattering losses [2], [4]. Nonlinear optical phenomena based on the two-wave mixing in a Silicon-SALC optical waveguide have been investigated theoretically in detail [5], [6]. FWM in the bulk SALC has been studied theoretically [7], [8]. It has been shown that the FWM caused by the light-induced smectic layer deformations in SALC results in the Brillouin enhanced FWM, phase conjugation, parametric generation of the harmonics with the combination frequencies, and the hydrodynamic flow [7], [8]. In this work, we studied theoretically FWM in Si-SALC optical waveguide. We solved simultaneously the Maxwell equations for the waveguide modes and the hydrodynamic equations for SALC in the FWM case. We have shown that the strong nonlinear interaction among the interfering optical waveguide modes takes place. We evaluated the smectic layer displacement dynamic grating caused by the interference of four waveguide modes and the slowly varying amplitudes (SVAs) of the interfering modes. It is shown that the optical phase conjugation of the waveguide modes is possible. FWM can be used for wavelength conversion (WC), parametric amplification and oscillation, tunable infrared and ultraviolet generation and optical phase conjugation in modern optical communication systems [1], [9].
Keywords: four-wave mixing (FWM), nonlinear optics, optical waveguide, smectic A liquid crystal (SALC), dynamic grating.
[1] Y.R Shen. The Principles of Nonlinear Optics. Wiley, Hoboken, New Jersey, USA, 2003.z
[2] I.-C. Khoo. Liquid Crystals. 2nd ed. Wiley, Hoboken, New Jersey, USA, 2007.
[3] D.C. Zografopoulos, R. Asquini, E.E. Kriezis, A. d’Alessandro and R. Beccherelli. Guided-wave liquid crystal photonics. Lab on a Chip, vol. 12, pp. 3598-3610, 2012.
[4] T. G. Giallorenzi, J.A. Weiss, and J.P. Sheridan. Light scattering from smectic liquid-crystal waveguides. Journal of Applied Physics, vol. 47, no. 5, pp. 1820-1826, 1976.
[5] B.I. Lembrikov, D. Ianetz, Y. Ben-Ezra. Nonlinear optical phenomena in silicon-smectic A liquid crystal (SALC) waveguiding structures. in 20th Int'l. Conf. on Transparent Optical Networks (ICTON 2018), Bucharest, Romania, paper Mo.D4.1.
[6] B. I. Lembrikov, D. Ianetz and Y. Ben-Ezra. Nonlinear optical phenomena in a silicon-smectic A liquid crystal (SALC) waveguide. Materials, 12, 2086, Jun. 2019, pp. 1-17.
[7] G.F. Kventsel and B.I. Lembrikov. The four-wave mixing and the hydrodynamic excitations in smectic A liquid crystals. Molecular Crystals and Liquid Crystals, 262, pp. 591-627, 1995.
[8] B.I. Lembrikov, D. Ianetz, Y. Ben-Ezra. Nonlinear optical phenomena in smectic A liquid crystals. In: Liquid Crystals – Recent Advancements in Fundamental and Device Technologies. Ed. P. K. Choudhury, IntechOpen, Croatia, 2018, pp. 131-157. [9] G. P. Agrawal. Fiber-Optic Communication Systems. Wiley, Hoboken, New Jersey, USA, 4th edition, 2010.

Aude Lereu
A new refractive index sensor based on enhanced surface field of zero-admittance layer in dielectric multi-layers
D. Niu¹, A. L. Lereu¹, M. Zerrad¹, A. Moreau¹, F. Lemarchand¹, J. Lumeau¹, V. Aubry², A. Passian³, J. A. Zapien⁴, and C. Amra^1
1Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France
²PSA Groupe, Direction Scientifique, Centre Technique de Vélizy, Vélizy-Villacoublay, France
³Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
⁴Center Of Super-Diamond and Advanced Films and Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong, SAR, PRC
Optical field enhancement plays a key role in applications such as chemical and biological detection, imaging or alternatively exchange of information and communication. Historically, thanks to plasmonic resonances, metals have dominated applications related to field enhancement and confinement for sensing and imaging [1-4]. Dielectrics, on the other hand, found a prominent role mainly in communication and waveguiding applications because of the associated low optical losses [5,6]. With the growing demands for chemical and biological sensing at higher sensitivity and selectivity, recent designs such as hybrid systems with the Tamm plasmons [7,8] or resonant all-dielectric multilayers [9-11] are gaining prominence. Such systems can be synthesized and optimized with the aid of the admittance formalism, commonly practiced in optical thin film design, leading to huge optical fields when working under total internal reflection [12-16]. Following our recent synthesis method, wherein a zero-admittance layer is deposited on a Bragg mirror [12, 17], we will explore the resulting field enhancement and confinement parameters, and therefore fully characterize the associated large ultra-sharp optical resonances. The strength and sharpness of these resonances are assets for low detection applications but require a well-controlled incident illumination and a highly accurate control over the geometric parameters of the multilayers. After evaluating such boundaries [18,19], we will fabricate and operate with optimized resonant dielectric multilayers in sensing configurations to evaluate both the achievable sensitivity and limit of detection. We will present our first experimental results involving different solutions with concentrations as low as 0.03%, corresponding to a refractive index variation of 6.10-5 [17]. The strong agreement with the theoretical predictions demonstrates the validity and utility of the presented sensing approach. The authors acknowledge the PSA group for financial support of this work, the ANRT for their support through the CIFRE program and the RCMO Group of the Institut Fresnel for the coatings realizations. This work is part of the OpenLab PSA/AMU: Automotive Motion Lab through the StelLab network.
[1] A. Passian, A. L. Lereu, A. Wig, F. Meriaudeau, et al, Phys. Rev B 71, 165418 (2005).
[2] E. Ozbay, Science 311, 189 (2006).
[3] A. Archambault, T. V. Teperik, F. Marquier, and J. J. Greffet, Phys. Rev. B 79, 195414 (2009).
[4] J. Homola, S. S. Yee, and G. Gauglitz, Sens. Actuators, B 54, 3 (1999).
[5] M. Tsang and D. Psaltis, Opt. Lett. 31, 2741 (2006).
[6] R. Kaiser, Y. Lévy, N. Vansteenkiste, A. Aspect, et al, Opt. Comm. 104, 234 (1994).
[7] M. Kaliteevski, I. Iorsh, S. Brand, R. A. Abram, et al Phys. Rev. B 76, 165415 (2007).
[8] B. Auguié, M. C. Fuertes, P. C. Angelomé, N. López Abdala, et al, ACS Photonics 1(9), 775 (2014).
[9] F. Michelotti, A. Sinibaldi, P. Munzert, N. Danz, and E. Descrovi, Opt. Lett. 38(5), 616–618 (2013).
[10] A. Sinibaldi, N. Danz, E. Descrovic, P. Munzert, et al, Sens. Actuators, B 174, 292 (2012).
[11] A. L. Lereu, M. Zerrad, A. Passian and C. Amra, Appl. Phys. Lett. 111, 011107 (2017).
[12] C. Amra, M. Zerrad, F. Lemarchand, A. L. Lereu, et al Phys. Rev. A 97, 023819 (2018).
[13] A. L. Lereu, M. Zerrad, C. N’diaye, F. Lemarchand and C. Amra, Appl. Opt. 53, A412 (2014).
[14] A. L. Lereu, M. Zerrad, M. Petit, F. De Fornel and C. Amra, Proc of SPIE Optics+Photonics 9162, 916219 (2014).
[15] C. N’diaye, M. Zerrad, A. L. Lereu, et al, Appl. Phys. Lett. 103, 131102 (2013).
[16] C. N’diaye, F. Lemarchand, M. Zerrad, D. Ausserre and C. Amra, Appl. Opt. 50, C382 (2011).
[17] D. Niu, M. Zerrad, A. L. Lereu, A. Moreau, et al, Submitted to PRA (2020).
[18] M. Zerrad, A. L. Lereu, C. N’diaye, F. Lemarchand and C. Amra, Opt Express 25, 14883 (2017).
[19] A. L. Lereu, F. Lemarchand, M. Zerrad, D. Niu, et al, Opt. Express 27, 30654 (2019).

Goran Mashanovich
Mid-infrared suspended group IV photonics
G. Z. Mashanovich¹, Y. Wu¹, A. Osman¹, Z. Qu¹, A. Sanchez-Postigo³, J. Soler-Penades¹, M. Nezhad², P. Cheben⁴, A. Ortega-Monux³, D. Pereira-Martin³, I. Molina-Fernandez³, R. Halir³, J. G. Wanguemert-Perez³, and M. Nedeljkovic^1
1Optoelectronics Research Centre, University of Southampton, UK
²School of Computer Science and Electronic Engineering, Bangor University, UK
³Universidad de Malaga, Dpto. de Ingenieria de Comunicaciones, ETSI Telecomunicacion, Spain
⁴National Research Council Canada, Ottawa, Canada
The mid-infrared wavelength region contains unique absorption fingerprints of many molecules and substances. Therefore, the main application area in the mid-IR can be sensing. Silicon and Germanium are transparent in this range and due to their excellent electrical and optical properties and CMOS compatibility they can offer suitable platforms for the realisation of compact mid-IR sensors. However, claddings used for the telecom wavelength range are usually not suitable at longer wavelengths due to high absorption, so alternative solutions need to be investigated. In this paper we present our recent results on suspended Si and Ge devices (waveguides, couplers and detectors) that can exploit full transparency ranges of Si and Ge.

Leonid Mochalov
Sensibilization of PbS materials by plasma annealing
L. Mochalov^1,2, A. Logunov¹, I. Prokhorov¹, D. Filatov³, A. Filatov³, A. Gorshkov³, A. Kudrin³, A. Knyazev³, N. Starostin³, A. Letnianchik³, and V. Vorotyntsev^3
1Nizhny Novgorod State Technical University n.a. R.E. Alekseev, Russia
²University of North Carolina at Charlotte, USA
³Lobachevsky University, Nizhny Novgorod, Russia
As-prepared PbS films independently on the method of preparation are all p-type semiconductors. The intrinsic p-type of PbS thin films without sensibilization is supposed to originate from the native defects i.e. structural imperfections and shallow accepter levels due to Pb vacancies. The large relativistic splitting in band structure of PbS materials makes them preferable for band gap engineering. In this work PbS thin films were prepared via direct plasma-chemical interaction of lead and sulfur vapors. Then, the as-prepared layers were annealed in argon-oxygen plasma. Optical emission spectroscopy (OES) was used to identify the exited species and to assume the possible mechanisms of plasma-chemical reactions. The changes in electrical properties and structure were also studied.
Keywords: lead sulfide, Mid-IR detectors, nanostructures, plasma annealing.

Igor Nefedov
Physical phenomena in hyperbolic epsilon-near-zero materials
I. Nefedov¹ and M. Rubi^2
1Aalto University, Finland
²University of Barcelona, Spain
Artificial and natural materials characterized by close to zero permittivity exhibit remarkable properties and attract significant attention due to their potential applications, particularly, for enhancement of different linear and nonlinear effects. In our presentation we will give a brief overview of known phenomena and discuss enhancement of the circular dichroism and the Casimir forces in hyperbolic epsilon-near-zero materials.

Kazuaki Sakoda
Features of mid-IR Dirac cones revealed by angle-resolved reflection and its selection rule
Y. Yao, N. Ikeda, T. Kuroda, T. Mano, H. Koyama, Y. Sugimoto, and K. Sakoda
National Institute for Materials Science, Tsukuba, Japan
We materialized the isotropic Dirac-cone dispersion relation in the mid infrared range by electron beam lithography of SOI (silicon-on-insulator) wafers. The dispersion relation was examined by the angle-resolved reflection spectra, which agreed quite well with numerical calculations and the selection rule derived by the k-p perturbation theory.

Silvia Schintke
Thin flexible semi-transparent optoelectronic sensors based on inkjet printable ZnO/PEDOT:PSS heterojunction
E. Frau¹, Yipeng Zhang², L. Viau², C. Filiâtre², and S. Schintke^1
1Laboratory of Applied NanoSciences, Department of Industrial Technologies, HEIG-VD, HES-SO / University of Applied Sciences Western Switzerland (HES-SO), Yverdon-les-Bains, Switzerland
²Institut UTINAM, UMR 6213 CNRS-UBFC, Université de Bourgogne Franche-Comté (UBFC), Besançon, France
Flexible sensors play an increasing role in printed electronics and are of interest for applications, e.g. in the field of flexible robotics and industrial automatization. In our study we have developed flexible optoelectronic sensors based on the hybrid inorganic-organic junction between ZnO and PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate). An ITO (indium tin oxide) layer on PET (polyethylene) foils was used as substrate electrode. ZnO was deposited from a nanoparticle suspension by electrophoretic deposition. For comparison, we have fabricated devices using three different methods of deposition of PEDOT:PSS, namely (i) drop casting, (ii) dip-coating, (iii) inkjet printing. For all devices, the current-voltage characteristic of the ZnO:PEDOT:PSS junction was recorded using miBotTM micromanipulators and analysed based on a Schottky-barrier model. The analysis of the junction shows, that all three deposition methods lead to a barrier height of 0.69 ± 0.01 eV. The obtained ideality factors of the junctions do also well compare for all three cases. Our results obtained for different layer thickness and different sizes of the active area, show that dip-coating and drop-casting can reliably be used for a rapid evaluation of the barrier height for the development of inkjet printable optoelectronic sensors. This work has been financially supported by INTERREG, Communauté du Savoir France-Suisse, project MACAFLEX 4.0.

Sebastian Schulz
Optical metasurfaces based on epsilon-near-zero materials: Towards low power nonlinear optics
S. A. Schulz, L. C. Wynne, and A. Di Falco
SUPA, School of Physics and Astronomy, University of St Andrews, UK
Nonlinear optics allows us to control the propagation of light using light itself. Unfortunately, typical nonlinear optical processes require high optical intensities, necessitating the use of short-pulsed laser. These systems are cumbersome and expensive, limiting the rollout of nonlinear processes to mass-market applications. However, recent work on epsilon-near-zero (ENZ) materials has shown that this class of materials can exhibit unprecedented nonlinear responses [1,2]. Here, we discuss the coupling of ENZ thin films to optical metasurfaces [3] as well as novel methods for characterising these devices. We will show that this coupling results in even stronger nonlinear responses [4] paving the way towards the ultimate dream of low power nonlinear optics.
[1] M. Z. Alam et al. Science 352, 795 (2016).
[2] L. Caspani et al. Physical Review Letters 116, 233901 (2016).
[3] S. A. Schulz et al. Physical Review A 93, 063846 (2016).
[4] M. Z. Alam et al Nature Photonics 12, 79 (2018).

Constantin Simovski
Can a plasmonic dimer nanoantenna be a spaser?
C. R. Simovski, Aalto University, Helsinki, Finland
From the theory of a spaser, it is known that the generation of a localized surface plasmon in the nanoantenna arises on condition of strong coupling corresponding to Rabi splitting of the fluorescence spectrum of molecules or quantum dots. In the continuous wave regime with growing pumping. the generation threshold is attained overcome if and only if the Rabi oscillations are non-radiative. In the present work we study this issue for two type of a plasmonic nanoantenna – a simple metal nanosphere and a dimer of such nanospheres with a tiny gap. In the first case we obtain the non-radiative regime of Rabi oscillations. In the second case, our simple classical model shows that it is impossible – the radiation of the system nanoantenna plus fluorescent emitter cannot be suppressed at both Rabi frequencies simultaneously. It is so because the plasmonic dimer is a very efficient nanoantenna – the corresponding Rabi splitting is very large. This result explains why a so efficient nanoantenna such as a plasmonic bowtie can be a nanolaser generating the polarization but cannot be a spaser.

Vincenzo Spagnolo
New developments in quartz-enhanced photoacoustic sensing real-world applications
M. Giglio¹, P. Patimisco¹, A. Sampaolo¹, Hongpeng Wu², Lei Dong², F. K. Tittel³, and V. Spagnolo^1
1PolySense Lab - Dipartimento Interateneo di Fisica, Technical University of Bari, Italy
²State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan, China
³Rice University, Department of Electrical and Computer Engineering, Houston, TX, USA
Optical gas sensors are excellent candidate as powerful tool for trace gas detection and monitoring in a large number of applications, such as environmental monitoring, industrial process control, biomedicine and petrochemical industry. Among most sensitive optical techniques, Quartz enhanced photoacoustic spectroscopy (QEPAS), which employs a quartz tuning fork (QTF) as resonant acoustic transducer, is one of the most sensitive and selective trace gas detection techniques [1]. QEPAS technique does not require an optical detector, allows the use of extremely small volumes, it is wavelength independent, it is immune to environmental noise. These factors, together with and its proven reliability, ruggedness and compactness represent the main distinct advantages with respect to other laser-based techniques for environmental monitoring and in situ detection. Starting from the basic principles governing the QEPAS technique, I will review the main results achieved by exploiting custom QTFs for QEPAS sensing and describe how these achievements allowed QEPAS real-word applications and lead to the first commercialization of QEPAS modules [2].
[1] P. Patimisco, A. Sampaolo, L. Dong, F. K. Tittel, V. Spagnolo, “Recent advances in quartz enhanced photoacoustic sensing”, Appl. Phys. Rev. 5, 011106 (2018).
[2] https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=11241

Anna Tasolamprou
Bound states sustained in dielectric photonic crystals and metasurfaces and wavefront manipulation
A. C. Tasolamprou¹, E. N. Economou^1,2, C. M. Soukoulis^1,3, T. Koschny³, and M. Kafesaki^1,4
1Institute of Electronic Structure and Laser, FORTH, Heraklion, Crete, Greece
²Department of Physics, University of Crete, Heraklion, Crete, Greece
³Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa, USA
⁴Department of Materials Science and Technology, University of Crete, Heraklion, Crete, Greece
We investigate the properties of bound surface modes sustained in media made of dielectric meta-atoms and in particular metasurfaces and photonic crystals. We discuss the origins of bound modes and demonstrate components that access wavefront control, in particular directional emission, frequency splitting and beam collimation achieved by coupling of the bound states to radiation modes through leaky wave radiation mechanism using properly designed scattering gratings.
Keywords: metasurfaces, flat optics, bound states, wavefront manipulation

Carmen Vázquez Garcia
Effect of the fiber’s core size on a two color pyrometer
A. Núñez-Cascajero, A. Tapetado, P. Contreras, A. Fresno, and C. Vázquez
Electronics Technology Department, Universidad Carlos III de Madrid, Leganés, Spain
Two color pyrometers are useful for measuring temperature in very precise locations with a fast response. We explore the importance of the effect of the fiber core on the measurements, due to its influence in the spatial resolution and in the temperature range that can be measured, along with target applications where those aspects are critical.

Guang Wu
Implications of carbohydrate binding modules of cellulases summarized from visualization
Shaomin Yan and Guang Wu
State Key Laboratory of Non-Food Biomass and Enzyme Technology, National Engineering Research Center for Non-Food Biorefinery, Guangxi Key Laboratory of Bio-refinery, Guangxi Academy of Sciences, Nanning, Guangxi, China
Cellulase is one of most important enzymes in biotechnology, and is generally structured in multiple domains, i.e. signal domain, catalytic domain, carbohydrate binding module (CBM) and linker. The CBM plays crucial roles in cellulosic hydrolysis including proximity effect, targeting, disrupting and amorphogenesis, and thus facilitates the association of soluble cellulases with insoluble cellulose. CBM can be classified into 81 CBM families according to their sequence similarity or classified into three types of CBMs according to their high-resolution structural similarity. Although not many studies have been directed to the visualization of CBMs, it necessarily reviews different visualization studies on CBMs at both meso- and nano-scale in order to understand the general patterns of CBMs under visualization. In this mini-review, we at first review the visual observations on how cellulase CBM acts on cellulose. Secondly, we attempt to generalize these observations from three aspects, i.e. cellulase CBM adsorption to cellulose, cellulase CBM occupying space in cellulose and cellulose surface accessibility to cellulase CBM. Thirdly, our generalizations are as follows: (i) the most effective crystal faces are 220 and 22 ̅0 for cellulase, (ii) cellulase could be more efficient to catalyse the cellulose chain composing of 50 cellobioses at least in order that CBM can hold cellulose, and (iii) a bunch of celluloses can be stratified into not only traditional amorphous and crystalline regions, but also disordered/dislocated region, and each region is subject to a specific type of CBM. Finally, we draw implications from these generalizations, (1) cellulases usually approach cellulose through 100, 11 ̅0 and 010 crystal faces although β(1→4) glycosidic bond is located near to crystal faces are 220 and 22 ̅0, and (2) it necessarily develops the ultra-small sized cellulases to access to fragment of cellulose because cellulases appear much larger for cellulose smaller than 50 cellobioses.
Keywords: carbohydrate binding module, cellulase, cellulose, microscopy, visualization.

Marc Wuilpart
Polarimetric optical fibre sensing for plasma current measurement in thermonuclear fusion reactors
M. Wuilpart¹, A. Gusarov², W. Leysen², P. Batistoni³, P. Moreau⁴, P. Dandu¹, and P. Mégret^1
1Electromagnetism and Telecommunication Department, Faculty of Engineering, University of Mons, Mons, Belgium
²SCK.CEN Belgian Nuclear Research Center, Mol, Belgium
³ENEA, Department of Fusion and Nuclear Safety Technology, Rome, Italy
⁴CEA Cadarache (IRFM), Saint-Paul-lez-Durance, France
For plasma current sensing in next-generation Tokamak thermonuclear fusion reactors like ITER and DEMO, optical fibre-based polarimetric sensors appear to be an alternative to conventional technologies (Rogowski coils, pick-up coils) thanks to a direct measurement of the plasma current (the polarization rotation is proportional to the current) and to an expected robustness against radiations. Optical fibre sensors also offer the possibility to avoid the use of a large number of electrical cables required in conventional technologies. In this talk, we propose to summarize our last results in FOCS (Fibre-Optics Current Sensor) and POTDR (Polarization Optical Time-Domain Reflectometer) sensors based on spun and low birefringence fibres. In particular, the accuracy of the proposed sensors will be discussed according to the spun fibre properties, Faraday mirror detuning, temperature and vibration effects. This study will be contextualized in the frame of the future ITER fusion reactor. Experimental results obtained on the JET tokamak for the FOCS approach and the TORE SUPRA tokamak for the POTDR approach will also be presented and discussed.
Keywords: current sensing, Faraday effect, fusion reactors, FOCS, POTDR, ITER, JET, TORE SUPRA.

Stephanos Yerolatsitis
Optical fibres for biomedical applications
S. Yerolatsitis¹, H. Wood¹, K. Ehrlich², A. Kufcsak², K. Dhaliwal², and J. Stone^1
1Department of Physics, University of Bath, UK
²EPSRC IRC Hub, Centre for Inflammation Research, Queen's Medical Research Centre, University of Edinburgh, UK
We are developing optical fibres for medical applications with aim to translate them to clinic. These speciality optical fibres are designed for imaging and Raman sensing, and provide an increased efficiency while maintaining a sub millimetre diameter size.

Ya Sha Yi
Metasurface lens with artificial focus pattern
Ya Sha Yi, Mao Ye, Vishva Ray, and Dachuan Wu
University of Michigan, Dearborn, USA
Metasurface lens as one of the most popular applications of emerging optical metasurfaces has raised widespread interest recently. With nano structures fully controlling phase, polarization and transmission, metalens has achieved comparable performance of commercial objective lenses. While recent studies seeking for the accomplishment of traditional focusing behaviors through metalens are successful, in this work, we have discovered that instead of focusing light to a point, metasurface further enables shaping the focus into flexibly designed patterns, with more promises and potentials. New mechanism and generalizations of conventional point-focused metalens guiding principles have been proposed with metalens concentrating light to artificial focus pattern. As proving examples, the metalens with ‘M’ shaped focus are fabricated and characterized. It is fabricated with a single layer of silicon-based material through CMOS compatible nano fabrication process. The mechanism to generate artificial focus pattern can be applied to a plethora of future on chip optical devices with applications ranging from beam engineering to next generation nano lithography.

Kivilcim Yuksel Aldoğan
An overview of the recent advances in FBG-assisted phase-sensitive OTDR technique and its applications
K. Yuksel¹, J. Jason², E. B. Kocal¹, M. Lopez-Amo Sainz³, and M. Wuilpart^2
1Electronics Engineering Department, Izmir Institute of Technology, Izmir, Turkey
²Electromagnetism and Telecommunication Department, Faculty of Engineering, University of Mons, Belgium
³Electrical and Electronics Engineering Department, Public University of Navarra, Pamplona, Spain
In this paper, we discuss the operation principles, sensing mechanism, challenges and application areas of FBG-assisted phase-sensitive optical time-domain reflectometer. A special emphasis is given to the interrogation of fiber Bragg grating arrays for vibration sensing application. Results obtained by different research groups are compared in terms of performance characteristics, and future perspectives. Recent progresses obtained through our research collaborations are also presented. In particular, the detrimental spectral shadowing effect and multiple reflection crosstalk are analysed and mitigation techniques are proposed.
Keywords: phase-OTDR, FBG, optical reflectometry, fiber optic sensors, distributed vibration sensing.

Yaping Zhang
Polyimide-coated fibre Bragg grating (FBG) sensors for thermal mapping of electric machine windings
Kun Shang¹, M. Galea³, V. Brusic¹, S. Korposh², and Yaping Zhang^1
1University of Nottingham Ningbo China, Ningbo, China
²The University of Nottingham, UK
³Key Laboratory of More Electrical Aircraft Technology of Zhejiang Province, China
This paper presents a design process and a prototype of a polyimide-coated fibre Bragg grating (FBG) thermal sensor system with fast tunable laser light source (up to 1kHz sensing frequency). This system was deployed to perform a comprehensive 2-D real-time radial and axial thermal profiling of an electromagnetic coil – the short duty cycle electric machine (EM) winding. The thermal measurements were first performed using a simulation prototype consisting of FBG interrogator, multi-FBG string temperature sensor, power resistors (thermal targets), and conventional thermocouples for reference measurements. The FBG measurement of copper winding were done in second experiment using a copper coil with FBG sensors system to measure radial and axial distribution of temperature. Our results indicate that the Polyimide-coated FBG sensor can be used for multi-point temperature monitoring of electromagnetic coils with the detection range of 20 – 200°C, spatial resolution of 6cm, and the error of measurement of ±2%. The resulting thermal maps can be used for hot spot localisation in electromagnetic coil systems.

 

TP invited presentations:

Björn Globisch
Experimental comparison of PIN and UTC photodiodes as continuous-wave terahertz emitters
S. Nellen¹, T. Ishibashi², L. M. Schwenson¹, R. B. Kohlhaas¹, L. Liebermeister¹, S. Breuer¹, A. Deninger³, M. Schell¹, and B. Globisch^1,4
1Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute, Berlin, Germany
²NTT Electronics Techno Corporation, Atsugi, Japan
³TOPTICA Photonics AG, Graefelfing, Germany
⁴Technische Universität Berlin, Institut für Festkörperphysik, Berlin, Germany
We provide the first-ever direct comparison of the terahertz (THz) output of fiber-coupled UTC- and PIN-based continuous-wave emitters. We investigated the influence of the optical power and the bias voltage on the THz output. As both emitters are characterized in the same setup, the observed differences can be traced back to the diode structure itself. We find large differences for frequencies below 350 GHz, where each device excels in a certain spectral range. Between 350 GHz and 1 THz, both emitters achieve a comparable THz output.

Martin Hofmann
Continuous wave THz system based on dual wavelength monolithic Y-branch laser diode
N. Surkamp², A. Gerling², J. O’Gorman¹, M. Honsberg¹, S. Schmidtmann¹, U. Nandi⁴, S. Preu⁴, J. Sacher³, C. Brenner², and M. R. Hofmann^2
1Sensor Photonics GmbH, Marburg, Germany
²Lehrstuhl für Photonik und Terahertztechnologie, Ruhr-Universität Bochum, Germany
³Sacher Lasertechnik GmbH, Marburg, Germany
⁴Terahertz Bauelemente und Terahertz Systeme, TU Darmstadt, Germany
In this work, a monolithic Y-branch laser diode is used for continuous wave Terahertz generation and detection. The output of the laser diode is fiber coupled, amplified and fed into a photoconductor based CW Terahertz setup. With this system, time domain measurements can be obtained using a fiber coupled delay stage. Moreover, sample thickness determination based on laser current induced frequency scanning will be presented.

Mauro Pereira
Design of GHz-THz nonlinearities in quantum structures
M. F. Pereira^1,2 and A. Apostolakis^2
1Department of Physics, Khalifa University of Science and Technology, Abu Dhabi, UAE
²Department of Condensed Matter Theory, Institute of Physics, Czech Academy of Sciences, Czech Republic
This talk starts with a short review of the state of the art in nonlinearities in the Gigahertz (GHz) to Terahertz range, followed by an outline of an hybrid approach combining Nonequilibrium Green's Functions and the Boltzmann equation for the nonlinear response of semiconductor superlattices. The nonlinearities are controllable in very good agreement with experiments [1-2]. The Terahertz-Mid Infrared (TERA-MIR) is relatively well understood [3-5] but more work is needed for the next step which is the GIGA-TERA-MIR extended range and a numerical tool is discussed to design materials and devices [6-7] for a large number of applications for the detection of substances which have strong GHz-THz resonances. In the second part of the talk, recent results of control of GHz-THz nonlinearities under different conditions will be discussed in detail.
[1] M.F. Pereira et al, Phys. Rev. B 96, 045306 (2017).
[2] M.F. Pereira et al, J. Nanophoton. 11 (4), 046022 (2017).
[3] M.F. Pereira, Opt. Quant. Electron. 47, 815 (2015).
[4] M.F. Pereira, Applied Physics Letters 109, 222102 (2016).
[5] M.F. Pereira and I.A. Faragai, Optics Express 22 (3), 3439 (2014).
[6] A. Apostolakis and M.F. Pereira, AIP Advances 9, 015022 (2019).
[7] A. Apostolakis and M.F. Pereira, J. of Nanophotonics 13, 036017 (2019).

Clara Saraceno
High-power ultrafast thin-disk lasers for THz generation
F. Meyer, T. Vogel, N. Hekmat, T. Vogel, A. Omar, S. Mansourzadeh, F. Fobbe, S. Ahmed, Y. Wang, M. Hoffmann, and C. J. Saraceno
Ruhr University, Bochum, Germany
Abstract: The performance of ultrafast laser systems has seen tremendous progress in the last decades, continuously giving momentum to many fields of science and technology. In particular, the average power of ultrafast sources has seen extremely fast increase. Nowadays, ultrafast laser systems delivering hundreds of watts to kilowatts of average power with pulse energies ranging from hundreds of microjoules to hundreds of millijoules start to be even commercially available, based on optimal geometries such as fiber, slabs and disks. In particular, disk lasers have consistently been at the forefront of latest progress. Their geometry is particularly well-suited for power and energy scaling of ultrashort pulses: the thin, disk-shaped gain medium combined with large mode areas, results both in nearly unrestricted power scalability, and low accumulated nonlinearities. Among these laser systems based on the disk technology, one particular technology has attracted attention as a potential path to achieve the desired level from a simple, one-box, multi-MHz repetition rate oscillator: modelocked thin-disk oscillators can reach hundreds of watts of average power with femtosecond pulses at multi-MHz repetition rate. Exponential progress in the achievable levels is only an illustration of their enormous potential. So far, these oscillators reach up to 350 W average power, and pulse energies up to 80 µJ, both based on Yb:garnet thin-disk lasers. This talk will review latest progress in the generation of high power ultrashort pulses using both laser oscillators and amplifiers. We will place particular emphasis on the disk geometry and will discuss next steps and challenges towards further scaling, as well as their use as driving sources for the generation of high-power sources ranging from the XUV to the THz spectral regions.

Grigorii Sokolovskii
Quantum-cascade lasers for mid-infrared and terahertz range
G. S. Sokolovskii, Ioffe Institute, St Petersburg, Russia
Quantum-cascade lasers (QCL) since the first proposal in 1971 and realization in 1994, attract great attention of the research community. To date, QCLs cover extremely wide spectral range including mid-infrared (3-19 um) and terahertz. The main QCL feature distinguishing them from the conventional semiconductor lasers (i.e. 'laser diodes') is their unipolarity resulting in the photon emission in the transition of an electron in the conduction band from one quantum level to another instead of recombination of an electron-hole pair. The talk will discuss not only the success of the mid-IR QCLs, including high-power and single-frequency operation but also two approaches to QCLs in THz range - direct THz and difference frequency generation in mid-IR.

Mikhail Vasilevskiy
Surface-plasmon-polariton-assisted diffraction of THz waves on a graphene-covered slit
Y. V. Bludov¹, B. Alexandre¹, N. M. R. Peres^1,2, and M. I. Vasilevskiy^1,2
1Center of Physics and Department of Physics, University of Minho, Braga, Portugal
²International Iberian Nanotechnology Laboratory (INL), Braga, Portugal
Transmission of plane electromagnetic wave through a tiny slit in a metal film covered by monolayer graphene is considered using a semi-analytical approach. It is shown that it gives rise to diffraction accompanied by the excitation of standing waves of surface plasmon-polaritons in graphene, localized over the slit. It manifests itself by characteristic peaks in the calculated absorption spectra in the THz range. It is shown that their spectral position depends on the refractive index of the material filling the slit and can be tuned either by the graphene doping level. Additionally, we clarify the physical nature of a low-frequency absorption band, which originates from the lowest order waveguide-type mode of bare slit.
Keywords: graphene, surface plasmon-polariton, diffraction, THz.

Xianbin Yu
THz photonic-wireless transmission with beyond 100 Gbit/s data rates
Xianbin Yu¹, Lu Zhang¹, Shi Jia², Xiaodan Pang³, Xianmin Zhang¹, and L. K. Oxenloewe^2
1College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou, China
²DTU Fotonik, Technical University of Denmark, DK-2800, Denmark
³Applied Physics Department, KTH Royal Institute of Technology, Sweden
THz photonics-based wireless communication provides a promising solution for future ultrafast wireless access with data rates approaching 100Gbit/s and beyond. In this talk, we will present our recent demonstrations on beyond 100Gbit/s THz photonic-wireless transmissions. We will also discuss some challenging aspects of driving THz communication systems towards Tbit.

 

WAOR invited presentations:

Michał Aibin
Traffic prediction in optical networks using graph convolutional generative adversarial networks
C. Vinchoff, N. Chung, T. Gordon, L. Lyford, and M. Aibin
British Columbia Institute of Technology, Vancouver, Canada
In this paper, we use a non-linear GCN-GAN model to predict burst events in the optical network. We model three distinct burst events as Plateau, Single-Burst and Double-Burst. Plateau represents the network under steady traffic, Single-Burst represents the network experiencing a rapid traffic spike followed by a steady decrease, and Double-Burst represents the network experiencing a rapid traffic spike followed by an unexpected greater traffic spike. We verify the model's effectiveness to predict these burst events by comparing it to a basic LSTM, which has been shown to outperform other state-of-the-art models.

Victoria Bueno
AI/ML techniques for IP traffic estimation in 5G/6G networks
S. Gómez-Egea, P. Viroonluecha, M.-V. Bueno-Delgado, and P. Pavón-Mariño
Telecommunication Networks Engineering Group, Technical University of Cartagena, Spain
Traffic in 5G/6G networks is expected to be characterized by a large variability and high peak-to-valley ratios. Making such networks practical from an economic point of view requires dynamic resource allocation algorithms that assign network capacity on-demand instead of worst-case overcapacity provisioning. Eventually, this puts extra pressure for researching on traffic forecasting and traffic characterization techniques that accurately predict how the traffic will behave in the short term, e.g. next hours, observing the past monitoring traces, to feed the dynamic resource allocation actions. In this sense, this paper presents and evaluates a set of traffic forecasting algorithms based on the application of AI/ML techniques.

Alberto Castro
Deep recurrent neural network aided routing, modulation, and spectrum assignment algorithm in elastic optical networks
A. Castro, School of Engineering, Universidad de la República, Montevideo, Uruguay
In this paper, we propose a traffic prediction method based on a deep recurrent neural network algorithm to assist the routing, modulation, and spectrum assignment algorithm in elastic optical networks. Network traffic prediction can be generalized as a process that extracts useful information from historical lightpath allocations and then determines future network resources assignments. Learning long-range dependencies that are embedded in time series is often an obstacle for most algorithms. In contrast, Long Short Term Memory (LSTM) solutions, as a specific kind of scheme in deep recurrent learning, promise to overcome the problem effectively. We show that the application of the developed strategy effectively reduces the network blocking probability when compare with baselines.

Domenico Di Mola
Opportunities for automation in open optical networks: The optical control loop (OCL)
D. Di Mola and G. Grammel
Juniper Networks
Introducing the OCL and why it became a closed distributed system in the past. This state of the industry creates an opportunity to open up the OCL by leveraging open source projects such as TIP (GNPy), OpenROADM and ONF (ONOS). We share thoughts about modern network control architectures and the fit of a centrally OCL as a starting point for potential Open Source activities automating provisioning in optical line systems.

Georgios Ellinas
Providing confidentiality in optical networks: Metaheuristic techniques for the joint network coding-routing and spectrum allocation problem
G. Savva, K. Manousakis, and G. Ellinas
Department of Electrical and Computer Eng. and KIOS CoE, University of Cyprus, Nicosia, Cyprus
In this work, novel metaheuristic algorithms are proposed to address the network coding (NC)-based routing and spectrum allocation (RSA) problem in elastic optical networks, aiming to increase the level of security against eavesdropping attacks for the network’s confidential connections. A modified simulated annealing, a genetic algorithm, as well as a combination of the two techniques are examined in terms of confidentiality and spectrum utilization. Performance results demonstrate that using metaheuristic techniques can improve the performance of NC-based RSA algorithms and thus can be utilized in real-world network scenarios.
Keywords: security, routing and spectrum allocation, network coding, simulated annealing, genetic algorithms.

Vincenzo Eramo
Study and evaluation of QoS degradation costs in optical-NFV network environments with resource allocations based on long short term memory prediction techniques
V. Eramo¹, T. Catena¹, F. G. Lavacca², and J. P. Perez Salazar^1
1DIET, ”Sapienza” University of Rome, Italy
²Fondazione Ugo Bordoni, Rome, Italy
The paper investigates the effectiveness of bandwidth prediction technique based on Long Short Term Memory recurrent neural networks for the resource allocation in Network Function Virtualization network architectures in which the datacenters are interconnected by an Elastic Optical Network. In particular we evaluate the under-provisioning costs that occurs when fewer resources than the needed ones are allocated and characterizes the QoS penalty cost to be paid by the provider because of the QoS degradation.

Miquel Garrich
INSPIRING-SNI: Investigating SDN programmability improving optical south- and north-bound interfaces
M. Garrich¹, A. Bravalheri2, and P. Pavón^1,3
1Universidad Politécnica de Cartagena, Spain
²High Performance Networks Group, Faculty of Engineering, University of Bristol, UK
³E-lighthouse Networks Solutions, Cartagena, Spain
Software Defined Networking (SDN) controllers decouple the forwarding data-plane actions, instructed via south-bound interfaces (SBI), from the logic control-plane decisions, which can be decided by network applications exploiting the north-bound interfaces (NBI). This paper overviews the achievements of INPIRING-SNI, a Marie Sklodowska-Curie Action that aims at enhancing programmability in optical SDN ecosystems from two perspectives: SBI for interacting with optical equipment and NBI for exposing programming abstractions that ease the development of network applications. INSPIRING-SNI focused on disaggregated approaches for SBI based on YANG models while proposing an innovative approach for the NBI based on the concept of network optimization as a service (OaaS) with an extension of the Net2Plan planning tool.
Keywords: API, Marie Sklodowska-Curie Action, optical networks, optimization, SDN.

Brigitte Jaumard
A link decomposition for the RMSA problem
Q. A. Nguyen and B. Jaumard
Computer Science and Software Engineering Department, Concordia University, Montreal, Canada
explosive growth of emerging applications and networking paradigms (e.g., Internet of Things (IoT), Software Defined Network (SDN), 5G) lead to the rapid development of elastic optical networks (EON) for the next generation backbone networks. EONs can set up bandwidth-variable super channels by grooming series of finer-granularity (e.g., 12.5 GHz or even 6.25 GHz) sub-carriers and adapting the modulation formats according to the quality of transmission (QoT) of lightpaths. In this study, we propose a new decomposition mathematical model that can solve exactly the EON provisioning problem with lightpaths satisfying the continuity and contiguity constraints while selecting a proper modulation scheme.

Ronald Romero Reyes
Techno-economic assessment of hybrid electrical-optical intra-data centre networks
R. Romero-Reyes¹, S. Sultana¹, V. V. Pai², and T. Bauschert^1
1Chair for Communication Networks, Technische Universität Chemnitz, Germany
²Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
In this paper we study the cost-efficiencies of the deployment of hybrid Intra-data centre networks that integrate electronic packet switching with optical circuit switching technologies. By using a bottom-up approach to network dimensioning, network solutions are designed for selected data centre sizes – given by the number of servers housed in the data centre – and for selected server port speeds, i.e. 10GbE, 25GbE, 40GbE and 50GbE. The total cost of network ownership (TCO) is assessed and compared against traditional packet-switched solutions, e.g. leaf-spine, fat-tree, Facebook 4-Post and the new Facebook fabric. The results show that for large data-centre sizes hybrid networks reduce the TCO w.r.t traditional solutions whilst minimizing the network energy consumption.

Hélio Waldman
Performance gains imparted by traffic-awareness in an elastic single link
H. Waldman¹, R. C. de Almeida Jr.², and R. C. Bortoletto^3
1Dept. of Communications, FEEC/Unicamp, Campinas, SP, Brazil
²Dept. of Electronics and Systems, UFPE, Recife, PE, Brazil
³Dept. of Computer Science, IFSP, São Paulo, SP, Brazil
This paper presents an analytical discussion of optimal spectrum allocation algorithms for an elastic optical single link under multiclass incremental and dynamic traffic with arbitrary rates per class. The performances of the optimal algorithms are then compared with the usual greedy algorithms (e.g. first-fit) in order to derive the performance gains imparted by traffic-awareness for incremental traffic. Both uniform and non-uniform traffic profiles, as well as greedy and non-greedy assignment policies, are considered. Finally, extension of these results to the case of dynamic traffic is briefly discussed.
Keywords: elastic single link, traffic-awareness, idleness minimization, incremental traffic.