A framework for analyzing in-band crosstalk accumulation in ROADM-based optical networks

Reconfigurable optical add-drop multiplexers (ROADMs) are central pieces in building transparent optical transport networks. However, due to physical limitations, these devices can be a source of in-band crosstalk, which affects the quality of the lightpaths routed and the network performance. Hence, to efficiently design optical networks it is important to study how this impairment is generated and to understand its dependency on relevant network parameters, such as the number of wavelengths used and the node degree. In this paper, we propose a framework to analyze the in-band crosstalk accumulation inside of ROADM-based networks. The framework computes the number of accumulated crosstalk terms in each link of a lightpath considering different physical topologies, as well as different routing and wavelength assignment strategies. An empirical formula is also derived for computing the maximum number of accumulated crosstalk terms as a function of the network parameters. We observe that in the majority of the studied cases, there is a complete agreement between the results of the proposed framework and the empirical formula.info:eu-repo/semantics/acceptedVersio

Physical Layer Aware Optical Networks

This thesis describes novel contributions in the field of physical layer aware optical networks. IP traffic increase and revenue compression in the Telecom industry is putting a lot of pressure on the optical community to develop novel solutions that must both increase total capacity while being cost effective. This requirement is pushing operators towards network disaggregation, where optical network infrastructure is built by mix and match different physical layer technologies from different vendors. In such a novel context, every equipment and transmission technique at the physical layer impacts the overall network behavior. Hence, methods giving quantitative evaluations of individual merit of physical layer equipment at network level are a firm request during network design phases as well as during network lifetime. Therefore, physical layer awareness in network design and operation is fundamental to fairly assess the potentialities, and exploit the capabilities of different technologies. From this perspective, propagation impairments modeling is essential. In this work propagation impairments in transparent optical networks are summarized, with a special focus on nonlinear effects. The Gaussian Noise model is reviewed, then extended for wideband scenarios. To do so, the impact of polarization mode dispersion on nonlinear interference (NLI) generation is assessed for the first time through simulation, showing its negligible impact on NLI generation. Thanks to this result, the Gaussian Noise model is generalized to assess the impact of space and frequency amplitude variations along the fiber, mainly due to stimulated Raman scattering, on NLI generation. The proposed Generalized GN (GGN) model is experimentally validated on a setup with commercial linecards, compared with other modeling options, and an example of application is shown. Then, network-level power optimization strategies are discussed, and the Locally Optimization Global Optimization (LOGO) approach reviewed. After that, a novel framework of analysis for optical networks that leverages detailed propagation impairment modeling called the Statistical Network Assessment Process (SNAP) is presented. SNAP is motivated by the need of having a general framework to assess the impact of different physical layer technologies on network performance, without relying on rigid optimization approaches, that are not well-suited for technology comparison. Several examples of applications of SNAP are given, including comparisons of transceivers, amplifiers and node technologies. SNAP is also used to highlight topological bottlenecks in progressively loaded network scenarios and to derive possible solutions for them. The final work presented in this thesis is related to the implementation of a vendor agnostic quality of transmission estimator for multi-vendor optical networks developed in the context of the Physical Simulation Environment group of the Telecom Infra Project. The implementation of a module based on the GN model is briefly described, then results of a multi-vendor experimental validation performed in collaboration with Microsoft are shown

Impact of in-band crosstalk in an optical network based on multi-degree CDC ROADMs

he most common optical networks nodes are known as reconfigurable optical add/drop multiplexers (ROADMs). The architecture and components of these nodes have evolved over the time to become more flexible and dynamic. Particularly, the wavelength add/drop structures of these nodes have become more complex and with new features such as colorless, directionless and contentionless (CDC). One of the main limitations of the optical networks physical layer, the in-band crosstalk, is mainly due to the imperfect isolation of the components inside these nodes. This crosstalk is enhanced, when an optical signal traverses a cascade of ROADM nodes. In this work, the impact of in-band crosstalk, optical filtering and amplified spontaneous emission (ASE) noise on the performance of an optical communication network based on a cascade of CDC ROADMs with coherent detection and the modulation format quadrature phase-shift keying with polarization-division multiplexing (PDM-QPSK) at 100-Gb/s is studied through Monte-Carlo simulation. Two architectures, broadcast and select (B&S) and route and select (R&S), and two possible implementations for the add/drop structures, the multicast switches (MCSs) and the wavelength selective switches (WSSs), were considered. The degradation of the optical communication network performance due to in-band crosstalk is assessed through the optical-signal-to-noise ratio (OSNR) calculation. In particular, an OSNR penalty of 1 dB due to in-band crosstalk is observed when the signal passes through a cascade of 19 CDC ROADMs with 16-degree, based on a R&S architecture and with add/drop structures implemented with WSSsOs nós das redes de comunicação ótica mais comuns são os multiplexadores óticos de inserção/extração reconfiguráveis (ROADMs – acrónimo anglo-saxónico de reconfigurable optical add/drop multiplexers). A arquitetura e componentes destes nós têm evoluído ao longo do tempo no sentido de se tornarem mais flexíveis e dinâmicos. Em particular, as estruturas de adição/extração destes nós, tornaram-se mais complexas e detêm novas características que oferecem as funcionalidades CDC (acrónimo anglo- -saxónico de colorless, directionless e contentionless). Uma das principais limitações do nível físico das redes óticas, o crosstalk homódino, deve-se principalmente ao isolamento imperfeito dos componentes presentes dentro destes nós. Este tipo de crosstalk tem um impacto ainda mais significativo quando o sinal ótico atravessa uma cadeia de nós baseados em ROADMs. Nesta dissertação, o impacto do crosstalk homódino, filtragem ótica e ruído ASE (acrónimo anglo-saxónico de amplified spontaneous emission) no desempenho de uma rede de comunicação ótica baseada numa cadeia de CDC ROADMs com deteção coerente e usando o formato de modulação PDM-QPSK (acrónimo anglo-saxónico de polarization-division multiplexing quadrature phase-shift keying) a um ritmo binário de 100-Gb/s é investigado através de simulação Monte-Carlo. Consideraram-se duas arquiteturas, B&S e R&S (acrónimos anglo-saxónicos para broadcast and select e route and select), e duas possíveis implementações para a estruturas de inserção/extração, os MCSs e os WSSs (acrónimos anglo-saxónicos de multicast switches e wavelengh selective switches). A degradação do desempenho da rede ótica devido ao crosstalk homódino foi obtida através do cálculo da relação sinal-ruído ótica. Em particular, obteve-se uma penalidade de 1 dB para esta relação devido ao crosstalk homódino quando o sinal percorre uma cadeia de 19 CDC ROADMs com grau 16, uma arquitetura R&S e estruturas de inserção/extração baseadas em WSSs

Impact of physical layer impairments on large ROADM architectures

Most of today’s optical networks, use reconfigurable optical add/drop multiplexers (ROADMs) as nodes. To become more dynamic and flexible, these nodes architectures evolved over the years. The colorless, directionless and contentionless functionalities are now standard, however, current architectures have poor scalability due to limitations on wavelength selective switches dimensions. Hence, due to constant increase in data traffic, current architectures might become a bottleneck to manufacture future large-scale ROADMs. In this work, the hardware cost and in-band crosstalk generation inside different large-scale ROADM architectures, is compared with conventional architectures. Moreover, an analysis of optical filtering, amplified spontaneous emission (ASE) noise and in-band crosstalk impact in the performance of an optical network, with nodes based on the most promising large-scale architecture, the interconnected A architecture, is performed. This performance is assessed through Monte-Carlo simulation with 16 point quadrature amplitude modulation with polarization-division multiplexing (PDM-16QAM) and PDM- 32QAM signals with 200 Gb/s and 250 Gb/s, respectively. Two architectures are considered for the interconnected A express structure, Broadcast and Select (B&S) and Route and Select (R&S). For the add/drop structure, a bank-based structure is considered. The maximum number of cascaded ROADMs, considering all the studied impairments, is 5 and 7 nodes for a 32 GBaud 16QAM signal, respectively, for B&S and R&S architectures. A 32QAM signal reaches 3 and 4 nodes, respectively, for B&S and R&S architectures. The main penalty in transmission is the ASE noise generated by optical amplifiers throughout the network, having the in-band crosstalk and optical filtering penalties a lower contribution.A maioria das redes óticas são atualmente compostas por multiplexadores óticos de inserção/extração reconfiguráveis (ROADMs, em inglês) nos nós, cuja arquitetura tem evoluído para se tornarem mais dinâmicos e flexíveis. As funcionalidades colorless, directionless e contentionless estão hoje normalizadas, no entanto, as arquiteturas atuais tornam-se pouco escaláveis para ROADMs de elevada dimensão, devido a limitações nos comutadores seletivos no comprimento-de-onda. Neste trabalho, a comparação entre os custos associados e a geração de crosstalk homódino em diferentes arquiteturas propostas para ROADMs de elevada dimensão e as arquitecturas tradicionais é efetuada. É também analisado o impacto da filtragem ótica, ruído de emissão espontânea amplificada (ASE, em inglês) e crosstalk homódino no desempenho de uma rede com nós baseados na arquitetura denominada "Interconnected A". A avaliação é feita através de simulação Monte-Carlo com sinais multiplexados por divisão na polarização e modulação de amplitude em quadratura, PDM-16QAM e PDM-32QAM a 200 Gb/s e 250 Gb/s, respetivamente. Foram consideradas duas configurações para os ROADMs estudados, Broadcast and Select e Route and Select (B&S e R&S, em inglês) e uma estrutura de inserção/extração denominada "bank-based". Quando considerados todos os efeitos, o alcance máximo da rede é de 4 e 7 nós para um sinal 16QAM, respetivamente, para configurações B&S e R&S. Para um sinal 32QAM, é de 3 e 4 nós, respetivamente, para configurações B&S e R&S. A principal penalidade na transmissão deve-se ao ruído ASE gerado nos amplificadores óticos ao longo da rede, tendo a penalidade devido ao crosstalk homódino e a filtragem ótica uma menor contribuição

Principles of Neuromorphic Photonics

In an age overrun with information, the ability to process reams of data has become crucial. The demand for data will continue to grow as smart gadgets multiply and become increasingly integrated into our daily lives. Next-generation industries in artificial intelligence services and high-performance computing are so far supported by microelectronic platforms. These data-intensive enterprises rely on continual improvements in hardware. Their prospects are running up against a stark reality: conventional one-size-fits-all solutions offered by digital electronics can no longer satisfy this need, as Moore's law (exponential hardware scaling), interconnection density, and the von Neumann architecture reach their limits. With its superior speed and reconfigurability, analog photonics can provide some relief to these problems; however, complex applications of analog photonics have remained largely unexplored due to the absence of a robust photonic integration industry. Recently, the landscape for commercially-manufacturable photonic chips has been changing rapidly and now promises to achieve economies of scale previously enjoyed solely by microelectronics. The scientific community has set out to build bridges between the domains of photonic device physics and neural networks, giving rise to the field of \emph{neuromorphic photonics}. This article reviews the recent progress in integrated neuromorphic photonics. We provide an overview of neuromorphic computing, discuss the associated technology (microelectronic and photonic) platforms and compare their metric performance. We discuss photonic neural network approaches and challenges for integrated neuromorphic photonic processors while providing an in-depth description of photonic neurons and a candidate interconnection architecture. We conclude with a future outlook of neuro-inspired photonic processing.Comment: 28 pages, 19 figure

Observing and Modeling the Physical Layer Phenomena in Open Optical Systems for Network planning and management

L'abstract è presente nell'allegato / the abstract is in the attachmen