Adaptive Compensation Of Polarization Mode Dispersion In WDM Systems

Polarization mode dispersion (PMD) is regarded as a severe, ultimate limitation in optical communication systems, especially in wavelength division multiplexing (WDM) systems. Therefore how to reduce its impacts is a vital subject in development of high-speed and long haul optical communication systems. However, it is very difficult to compensate the PMD effect because of its stochastic feature. The PMD compensation method in WDM optical communication systems and the adaptive high-order PMD compensation techniques are mainly discussed. Above all, the research works in the dissertation are summed up as following:In this thesis the coupled nonlinear Schr?dinger equation is solved by means of split-step Fourier transform. The coupled nonlinear Schr?dinger equation in eight-channel WDM systems is numerically solved and the effects of PMD on WDM systems are analyzed. The eye diagrams and the degrees of polarization (DOP) after propagating 100km are obtained. Conclusion is that the influence of PMD on each channel is different, which would be considered with the development of adaptive compensation of PMD in WDM optical fiber communication systems.A new method called the worst channel equalization (WCE) scheme is presented for adaptive compensation of PMD in WDM systems, where the third-stage optical polarization mode dispersion compensators are adopted to reduce the PMD-induced system impairments. The DOP which commonly referred to as the PMD feedback signal and the particle swarm optimization (PSO) algorithm which is the searching algorithm are both used for the PMD compensation. Numerical simulation results after compensation show that both DOP and opening of eye diagrams of each compensated channels are improved. In WDM system, there is a criterion that the DOP should be no less than 0.84. According to numerical simulation results, the channels which have been compensated are all up to the mustard. In general, the WCE scheme is an effective way for adaptive compensation of PMD in WDM systems.