The Study Of Polarization Mode Dispersion Mitigation And Compensation In WDM Systems

Polarization-mode dispersion (PMD) compensation in multi-channel WDM system is still a challenging problem. How to eliminate the effect of PMD effectively becomes a research hotspot in optical fiber communication system. Particle swarm optimization (PSO) algorithm is introduced into PMD compensation in WDM systems using a single PMD compensator, based on the strategy of compensating the worst channel and making the balance; New modulation formats as the advanced modulation format compared with the traditional OOK format are used to mitigate PMD and better performance are obtained; RS code is introduced into the PMD compensation and mitigation scheme and good performance is obtained; A new scheme of PMD compensation and mitigation based on Polarization-Time Coding and Turbo code is proposed, which can achieve great PMD mitigation performance and good BER improvement. In short, advanced PMD compensation technology, and PMD mitigation technology such as new modulation format, FEC and PTC are combined dynamically, offering improved solutions for adaptive PMD compensation in high-speed long haul WDM systems, and providing useful reference for theoretical studies and practical applications .The research works in the dissertation are summarized as follows:The basic concepts of PMD and various compensation methodsare reviewed and summarized. The PMD compensationtechnology in feedback optical compensation and the study ofusing DOP as the feedback control signal are discussed in detail.PSO algorithm is introduced to PMD compensation in WDM systems using a single PMDC, based on the strategy of compensating the worst channel and making the balance. The DOP values, residual differential group delay (DGD), and also the eye diagrams before and after compensation are obtained, they are obviously improved than before and good performance is obtained. DPSK and DQPSK modulation formats are used to achieve better PMD mitigation performance than OOK format. The performance of DPSK and DQPSK format has 3dB better than that of OOK format. DQPSK has the best PMDC mitigation performance than both the OOK and DPSK formats because it can double WDM spectrum-packing efficiency and upgrade the system capacity while has the same mitigation performance as DPSK format.The principles of RS encoding and decoding are introduced and RS code is introduced to the WDM multi-channel PMD compensation and mitigation scheme. From the results, RS code decrease the BER of the system, increase the tolerance for PMD, Q value and so on, which is conducive to the long-distance high-speed transmission.A new scheme based on Polarization-Time Coding (PTC) techniques and Turbo code to compensate PMD is proposed and simulated. PTC eliminiate the effect of PMD and Turbo code decreases the BER of the system, and good overall performance is obtained. From the results, the performance of Alamouti code is much better than VBLAST and Golden. There is almost no significant difference between the performance of Golden and VBLAST code, they both perform 3dB worse than Alamouti code. But, the rate of Alamouti code is half as VBLAST and Golden code. The performance of QPSK modulation behavior is quite similar as that for BPSK modulation. The only difference is that the performance of QPSK is 3 dB better than that of BPSK.