Research On Digital Signal Processing Algorithm Of Pdm-Co Communication System

This thesis is mainly about the principle of the polarization multiplexing-coherent optical communication, algorithms about linear damage compensation and orthogonal division frequency multiplexing. It focuses on studying and researching polarization demultiplexing by theoretical analysis, simulation and experiment. The phase noise and frequency offset in OFDM are also studied by simulation and theoretical analysis. The main content and creative points are:(1) The physical model of fiber was summarized. We research the theory of the coherent receiver, the process and algorithm of the polarization multiplex-coherent optical communication. We also talk about the principle about OFDM.(2) We study and research the model of polarization transmission channel, the polarization demultiplexing algorithm in single carrier and OFDM. A detailed study and research about polarization demultiplexing in stokes space (which called SS) was given. Due to the algorithm degrade when it facing time-varying polarization transmission channel in OFDM modulation, we propose an iterative algorithm (which called SS-adp) to overcome this problem. We demonstrate SS-adp has no singular problem and could using PDL compensation algorithm without complex computation.(3) The simulation and experiment about polarization multiplexing-coherent optical communication were built. We show that all digital signal processing could work in simulation and experiment, for example, frequency offset compensation, phase noise compensation and channel estimation. By introducing time-varying polarization channel, we show that SS-adp has a 6.78dB max improvement than SS. SS-adp with PDL compensation has a 2.5dB improvement than without it. By observing the stokes vectors of signal, We found that SS degrade cause the stokes vectors degrade and can’t be treated as a plane to found the inverse of the matrix. accurately. We demonstrate this by experiments which fiber length is 50km. In experiment, SS-adp has a 2.63dB max improvement than SS. SS-adp with PDL compensation has a 0.7dB improvement than without it.(4) We study the relation between the laser linewidth, subcarrier bandwidth, the length of OFDM symbol and the damage which caused by frequency offset and phase noise by formula. We point out that the DCS based on PCTW could not only mitigating the ICI caused by phase noise, but also ICI by fraction frequency offset. Then, we prove it by simulation.