Blind adaptive equalization for QAM signals: New algorithms and FPGA implementation.

Adaptive equalizers remove signal distortion attributed to intersymbol interference in band-limited channels. The tap coefficients of adaptive equalizers are time-varying and can be adapted using several methods. When these do not include the transmission of a training sequence, it is referred to as blind equalization. The radius-adjusted approach is a method to achieve blind equalizer tap adaptation based on the equalizer output radius for quadrature amplitude modulation (QAM) signals. Static circular contours are defined around an estimated symbol in a QAM constellation, which create regions that correspond to fixed step sizes and weighting factors. The equalizer tap adjustment consists of a linearly weighted sum of adaptation criteria that is scaled by a variable step size. This approach is the basis of two new algorithms: the radius-adjusted modified multitmodulus algorithm (RMMA) and the radius-adjusted multimodulus decision-directed algorithm (RMDA). An extension of the radius-adjusted approach is the selective update method, which is a computationally-efficient method for equalization. The selective update method employs a stop-and-go strategy based on the equalizer output radius to selectively update the equalizer tap coefficients, thereby, reducing the number of computations in steady-state operation. (Abstract shortened by UMI.) Source: Masters Abstracts International, Volume: 45-01, page: 0401. Thesis (M.A.Sc.)--University of Windsor (Canada), 2006

Impacto de imperfeições do laser em receptores ópticos coerentes com formatos de modulação de alta ordem

Orientador: Darli Augusto de Arruda MelloDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Atualmente, os sistemas ópticos coerentes transmitem grandes volumes de informação graças à utilização de formatos de modulação de alta ordem. No entanto, esses formatos de modulação são mais suscetíveis a perturbações de fase geradas por imperfeições nos lasers utilizados no transmissor e receptor. Este trabalho centrou-se em uma análise das imperfeições do laser e seu impacto sobre o desempenho de receptores ópticos coerentes com formatos de modulação de alta ordem. Em especial, avaliaram-se as duas fontes principais de perturbações de fase: o ruído de fase do laser e as flutuações na frequência de operação, efeito conhecido como jitter de frequência da portadora. Primeiramente, investigou-se o impacto das imperfeições do laser por meio de simulações. O ruído de fase foi simulado como um processo discreto de Wiener, e o jitter de frequência foi modelado como uma forma de onda senoidal. Os resultados permitiram avaliar o comportamento do sistema sob diversas condições de frequência e amplitude do sinal de jitter. Posteriormente, o impacto das perturbações de fase foi avaliado por meio de experimentos. Observou-se que parâmetro de largura de linha calculado por métodos existentes não é suficiente para prever o comportamento dos algoritmos de processamento digital de sinais sob condições intensas de jitter. Alternativamente, o trabalho sugeriu uma metodologia mais conveniente para prever o impacto das perturbações do laser no desempenho do sistema, que leva em consideração a composição de ruído de fase e jitter de frequênciaAbstract: Currently, coherent optical systems transmit large volumes of information thanks to the use of high-order modulation formats. However, such modulation formats are more susceptible to phase perturbations generated by imperfections in the lasers used in the transmitter and receiver. This work focused on an analysis of laser imperfections and their impact on the performance of coherent optical receivers with high-order modulation formats. In particular, the two main sources of phase perturbations were evaluated: laser phase noise and fluctuations in the operating frequency, an effect known as carrier frequency jitter. First, the impact of laser imperfections was evaluated by simulations. Phase noise was modeled as a Wiener process, and frequency jitter was assumed to be sinusoidal. The results allowed to evaluate the behavior of the system under different conditions of frequency and amplitude of the jitter signal. Later, the impact of phase perturbations was evaluated through experiments. It was observed that the laser linewidth calculated by existing methods is not sufficient to predict the behavior of the digital signal processing algorithms under intense jitter conditions. Alternatively, the work suggested a more convenient methodology for predicting the impact of laser perturbations on system performance, which takes into account the composition of phase noise and carrier frequency jitterMestradoTelecomunicações e TelemáticaMestra em Engenharia ElétricaCAPE

Optics for AI and AI for Optics

Artificial intelligence is deeply involved in our daily lives via reinforcing the digital transformation of modern economies and infrastructure. It relies on powerful computing clusters, which face bottlenecks of power consumption for both data transmission and intensive computing. Meanwhile, optics (especially optical communications, which underpin today’s telecommunications) is penetrating short-reach connections down to the chip level, thus meeting with AI technology and creating numerous opportunities. This book is about the marriage of optics and AI and how each part can benefit from the other. Optics facilitates on-chip neural networks based on fast optical computing and energy-efficient interconnects and communications. On the other hand, AI enables efficient tools to address the challenges of today’s optical communication networks, which behave in an increasingly complex manner. The book collects contributions from pioneering researchers from both academy and industry to discuss the challenges and solutions in each of the respective fields

Compensation of fibre impairments in coherent optical systems

Tese de mestrado integrado. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 201