CARRIER RECOVERY AND PERFORMANCE MONITORING FOR COHERENT OPTICAL COMMUNICATIONS

Abstract

We consider several aspects of optical communications. First, we consider low-latency carrier phase estimation that is crucial for future high-speed networks. Using a new analytical technique, we developed a generalization of the Viterbi-Viterbi Mth-power carrier estimator to explicitly deal with the effects of phase noise due to the semiconductor lasers. Accurate carrier recovery is not only important for coherent detection of higher-order modulations with increased spectral efficiency. It is also useful for on-line monitoring of the parameters of an optical link such as the signal-to-noise ratio (SNR) and the laser linewidth. Thus, we developed accurate optical performance monitoring techniques based on our carrier recovery methods. Finally, to facilitate the performance analysis of optical communications systems, we developed an accurate and easy-to-invert lower bound on the Gaussian Q-function that enables us to analyze the effects of laser linewidth on thse SNR penalty and the loss of spectral efficiency of digital modulations.