| Recent 30 years, optical fiber has became the primary and ideal transmission medium not only in communication system but also in many key application areas, for it's characteristics of low losses, strong anti-jamming capability, and broad bandwidth. But there are birefringence and polarization in single-mode optical fiber. The polarization mode dispersion (PMD) caused by birefringence leads to pulse broadening, now PMD has been regarded as a limitation for development of high-speed optical communication system. Meanwhile, the random variation in the birefringence polarization of an optical fiber along its length causes unstable output polarization state, which is a bad impact on some specific application areas.This thesis consists of two parts.The first part of this thesis, based on coupled nonlinear Schrodinger equation, the impacts of initial chirp on the PMD were simulated and analyzed with Split-step Fourier Method. The results show that: when the pulse propagates in the anomalous dispersion fiber, the co-effects of initial positive chirp, second-order dispersion and nonlinear effects compress the pulse, and compensate pulse broadening induced by PMD, then inhibit the PMD's impacts on system;The chirps shouldn't be too large and they exist optimum values, which are around 0.5. Moreover, in this part, we also analyzed the impacts of pulse's initial power to the Q-C curve.In the second part, we researched on the distortion resulted by propagation of pulse originated from the Front-End laser system. The results show that: the pulse can't keep it's linear polarization state due to the random birefringence of the optical fiber, and the strong nonlinear effects in high-power system cause the distortion of the pulse at the two polarization direction. Finally, the feasibility that polarization maintaining fiber resolve the pulse distortion problem was simulated and analyzed. All of above will provide theoretic reference for setting down the resolve scheme. |
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