Electronic Compensation Of Polarization Mode Dispersion Based On Adaptive Algorithm

With the development of optical fiber communication systems which are large-capacity and long-haul, the polarization mode dispersion (PMD) is a big limitation for the high-speed and long-distance optical fiber transmission systems.PMD causes the inter-sysmbol interference which lead to the deteriotation of the system, thus it is needed to take effective steps. The compensator working in optical domain has the complex technology and high cost, so the commercial PMD compensation technology hasn't been applied widely.However,the compensation technology in electrical domain can eliminate the inter-sysmbol interference caused by PMD with low-cost,and reduce the effect of the fiber non-linear,it can compensate adaptively. So it has a wide prospect for the electrical compensation technology.The effects of PMD to optical fiber communications systems are simply analyzed, and the compensation technologys of the polarization mode dispersion are generalized. Based on these research, the imitate model of the optical communication system with the PMD and gauss noise is built, three equalizers are designed (the linear feed-forward equalizer, the decision feed-back equalizer and the maximum-likelihood sequence estimation equalizer) to equalize the system distortion, and the design and simulation of the first-order PMD electrical domain equalizer are realized.First the the linear feed-forward equalizer and the decision feed-back equalizer are designed based on the least mean-square algorithmic,compare and analyse the structure of the two equalizer .Emphatically discuss the tap numbers of the decision feed-back equalizer to the effect of equalization , and analyse the performance of the kinds of structure through simulation eyediagram, the results show that the decision feed-back equalizer is good at compensating the nonlinear loss caused by PMD.Secondly the maximum-likelihood sequence estimation equalizer is designed based on the Viterbi algorithmic. The Viterbi algorithmic can overcome the question of the large calculation to a certain extent. Finally, the performance of the three equalizers are compared in the same condition .the result show that the maximum-likelihood sequence estimation equalizer has better compensation performance than the other two equalizers. All the equalizers designed in this paper can compensate the system disorderation caused by PMD. In practical application, we can choose different type equalizer according to the condition of the channel, the performance and complexity of the equalizer.