Artificial Neural Network Symbol Estimator With Enhanced Robustness to Nonlinear Phase Noise

This letter reports a novel approach for nonlinear phase noise mitigation, based on artificial neural networks (ANNs) tailored to classification applications and a pre-processing stage of feature engineering. Starting with a set of proof-of-concept simulations, we verify that the proposed system can achieve optimal performance for the additive white Gaussian noise (AWGN) channel. Then, considering a dispersion-less channel with strong nonlinear phase noise (NLPN) distortion, we demonstrate a Q-factor increase of 0.4dB, comparing with standard carrier-phase estimation (CPE) followed by minimum distance detection. Finally, simulating the propagation of 64Gbaud PM-16QAM over standard single mode fiber (SSMF), we verify that the ANN-based solution is effective on wavelength-division multiplexing (WDM) transmission conditions, enabling to increase the maximum signal reach by approximately 1 fiber span over the legacy CPE-enabled NLPN compensation

Rapidly adapting primary care sentinel surveillance across seven countries in Europe for COVID-19 in the first half of 2020: strengths, challenges, and lessons learned.

International audienceAs the COVID-19 pandemic began in early 2020, primary care influenza sentinel surveillance networks within the Influenza - Monitoring Vaccine Effectiveness in Europe (I-MOVE) consortium rapidly adapted to COVID-19 surveillance. This study maps system adaptations and lessons learned about aligning influenza and COVID-19 surveillance following ECDC~/~WHO/Europe recommendations and preparing for other diseases possibly emerging in the future. Using a qualitative approach, we describe the adaptations of seven sentinel sites in five European Union countries and the United Kingdom during the first pandemic phase (March\textendash September 2020). Adaptations to sentinel systems were substantial (2/7 sites), moderate (2/7) or minor (3/7 sites). Most adaptations encompassed patient referral and sample collection pathways, laboratory testing and data collection. Strengths included established networks of primary care providers, highly qualified testing laboratories and stakeholder commitments. One challenge was the decreasing number of samples due to altered patient pathways. Lessons learned included flexibility establishing new routines and new laboratory testing. To enable simultaneous sentinel surveillance of influenza and COVID-19, experiences of the sentinel sites and testing infrastructure should be considered. The contradicting aims of rapid case finding and contact tracing, which are needed for control during a pandemic and regular surveillance, should be carefully balanced

Optical Transponders

The first commercial 10 - Gb/ s transponders, deployed in the mid 1990s, were based on a very simple modulation technique, i. e., a binary light intensity modulation with envelope detection by a single photodiode. To extend the fiber capacity, bandwidth-efficient modulation techniques such as duobinary line coding and multilevel intensity-modulation formats gained popularity in optical communications in the late 1990s. In the following years, the use of differential phase modulation in combination with interferometric detection allowed the transponder data rates to be increased up to 40Gb/s. However, despite all improvements, the system performance of these 40 - Gb/ s solutions was still not on par with state-of-the art 10 - Gb/ s systems at that time. With the advent of coherent detection, things suddenly changed and transmission rates of 100Gb/s and beyond could soon be achieved, thanks to the use of high-order modulation formats and advanced digital signal-processing techniques. In this chapter, the configuration and performance of the most common transmitter and receiver combinations that are currently used in optical transmission systems will be described, including an overview of transponder types and their hardware architectures. Finally, relevant standards will be discussed and pluggable optical transceiver modules used in modern transponder implementations will be explained