Studies On Real-Time Coherent Receivers In Optical Communication System

Because of the high efficiency of frequency, and high sensitivity of coherent receiver, digital coherent receivers become an encouraging receiving’ method in long-haul system. At the same time, it can compensate for various types of losses, which makes it an important part of next generation optical communication system. Many domestic and foreign research centers, companies and schools have invested enormous finance, material and human resource on it.In this paper, we have studied the theory of coherent receivers in optical communication system and given system-level simulation on it. We have also done some research on how to compensate for polarization mode depend effects,. and successfully given simulations on coherent receivers in a43Gb/s optical communication system. My main work is listed as follows:(1) The background and current situation of coherent receiver in optical communication system is elaborated, study situation of both domestic and foreign country is shown, and the importance of coherent receivers in next generation optical communication system is also given.(2) Effects of optical fiber on signals transmitted in it are presented, and methods or ways to compensate for these effects is given.(3) The basic theory of coherent receivers in optical communication system is described, and simulation platform for real-time coherent system is built on VPI.(4). Conventional algorithm for compensating for polarization-mode-dispersion is improved to meet the requirements of real-time and high-speed needs, and a new algorithm of parallel and pipelined const modulus algorithm is proposed. Besides, we have given some optimizations on it between bit error ration and usage of resources in FPGA.