Connectivity is the major driver in the modern “information society”, where the range of data-driven applications is exploding, and new information-based value chains are rapidly emerging. Optical networks are the backbone of the global communication infrastructure, interconnecting billions of people and a huge number of various autonomous devices, control systems, and machines. Optical systems’ development incites the skyrocketing growth in the demand for data exchange and harnessing, fuelled by webbased services such as ultra-HD streaming, cloud services, 5G proliferation, fostering the changes in the digital world, and shaping the structure of the modern society. The demand growth is especially pronounced in the access and metro links, where data rates largely exceeding the current <1 Tb/s will be required. Moreover, the COVID-19 – with the huge number of people working from home – has intensified the pressure on the optical networks. Also, features such as the financial cost of the system elements, latency, dynamic reconfigurability, and energy consumption gain progressively more importance for the new generation of access and metro networks. The Doctorate Network NESTOR will answer the How? When? and Where? coherent optical transceiver will be deployed in metroaggregation optical networks to meet the demand for new cost-efficient solutions. NESTOR will also address the Who? by providing advanced training to 10 Fellows - from a new generation of engineers - with PhD projects significantly expanding the flexibility and capacity of access/metro networks. NESTOR harnesses the complementary expertise of the top academic groups (Aston, PoliTO, UPC, SSSA, and TU/e) and core telecom industry (Infinera, BT, Orange, SM-Optics, VPI and Ericsson). NESTOR will provide Fellows with a uniquely broad education ranging from recent advances in ML&AI to real-world telecom engineering, which will enable them to design and implement high-capacity access and metro networks.

One major goal in this project is to develop an analytical formulation,as well as a stochastic Monte-Carlo (MC) simulator, that allow us to study in a rigorous way the impact of in-band crosstalk, both incoherent and coherent, originated in CDC ROADMs in the performance of flexible grid networks, considering 16-QAM and 64-QAM 400 Gbps signals.On a network-side perspective, the emergence of modulation formats with higher-order constellations and, consequently, with stricter performance margins has increased the importance of physical impairment awareness in the network planning process. Thus, it is essential to incorporate the effects of in-band crosstalk, along with other effects, in an impairment-aware routing and spectrum assignment (RSA) framework. This framework should be able to efficiently provision paths and spectrum for superchannels based on M-QAM carriers in a CDC-ROADM network, while using the physical model as a performance validation tool for candidate optical paths

Neste projecto, desenvolvem-se e analisam-se modelos para a caracterização estatística dos efeitos da ICXT em MCFs, propõem-se técnicas para a mitigação daqueles efeitos em redes baseadas em MCF, e usam-se aqueles modelos e técnicas no desenvolvimento de algoritmos de encaminhamento e alocação de espectro e núcleo (RSCA) em redes ópticas elásticas (EONs). O projecto foca-se principalmente em estudos de simulação e teóricos sobre a caracterização estatística dos efeitos da ICXT em MCF e sobre técnicas de modulação para mitigação daqueles efeitos em redes baseadas em MCF. Estes estudos são complementados pela realização de demonstrações laboratoriais dos principais resultados de simulação e teóricos. O projecto tira proveito dos conhecimentos de trabalho experimental (em laboratório) e de projecto de sistemas baseados em tecnologia de MCFs do NICT (National Institute of Information and Communications Technology, Japão) combinado com a experiência do IT (Grupo de Comunicações Ópticas do pólo de Lisboa do Instituto de Telecomunicações) na modelação teórica e análise de sistemas e redes de telecomunicações por fibra óptica.

This project is within the optical communication networks area. In particular, in the area that studies the physical constraints in optical networks.One of the most severe limitations in the network physical layer is crosstalk. This phenomenon has its origin, primarily, in the imperfect isolation of optical components, such as optical switches, multiplexers, and demultiplexers, that are key components in the design of an optical node. The type of crosstalk that causes the higher degradation to the system performance is the in-band crosstalk, in which the interfering (crosstalk) signals and the selected signal, despite coming from distinct optical sources, have the same nominal wavelength.The main objectives of this project are:* Develop a formalism to evaluate the impact of in-band crosstalk in optical DQPSK systems.* Evaluate the impact of in-band crosstalk in a DPSK and DQPSK systems when the signal propagates through an optical network. Each optical node is formed by an optical switching architecture, optical amplifiers, optical filters, and possibly wavelength converters. * Implement Monte Carlo (MC) simulation to study the impact of ASE noise and in-band crosstalk on the performance of DPSK and DQPSK systems and confirm the analytical results.* Implement the multicanonical Monte Carlo (MMC) method to simulate the tails of the probability density function of the decision variable and to obtain lower values of the bit error rate (BER) than in the MC standard procedure.* Evaluate by simulation the impact of in-band crosstalk in optical networks with DPSK and DQPSK signals, for a rigorous model of the optical node and validate the analytical tool developed for this case.