Research On PMD Effect In High-speed Optical Fiber Communication System

With people's increasing demand on communication band width in recent years, fiber communication backbone network is developing towards high-speed, great capacity and long distance in a single channel. Especially after the utilization of Erdium-doped fiber amplifier (EDFA) and various techniques of dispersion compensation, fiber loss and chromatic dispersion are no longer the main limiting factor of transmission distance systems. However, it brings about another problem that constantly added up in the course of transmission , formerly negligible PMD (Polarization Mode Dispersion) has badly influenced the optical fiber communication systems. Research shown that when the transmission speed of systems is up to 10Gbit/s or above, Polarization Mode Dispersion (PMD) can noticeable damage the transmission performances of systems and became the final decisive factor limiting the transmission speed and distance of the high-speed optical fiber communication system. So it is an urgent problem to study how to deal with the impact of PMD on the transmission systems. However, it is very difficult to overcome the PMD effect because of its stochastic feature.The impact of PMD on high-speed data transmission and the key technologies of PMD compensation are the focus of optical fiber communication system in the world. The basic research task about PMD includes the fundamental theory, the PMD emulator and the techniques of measurement and compensation.Firstly, a summary of the principle of PMD and its statistics nature was given in this paper, which includes its concept, statistics nature, impact on the communication system and the techniques of measurement and compensation. Because of statistics nature of PMD it is necessary to design a PMD emulator in our research. So in the consequently we will analyze the principal state polarization (PSP) of PMD and study the statistical characteristics of the first and second order PMD of a PMD emulator based on the Jones matrix of optical fiber and Monte Carlo method. Research indicates that with increase of the segments of the polarization maintaining fiber, the simulating result of One-order and two-order PMD is closer to theoretic curve. Then we compared two sorts of designing methods of PMD emulator .The results will be helpful for PMD emulator design. Next, we gave a summary analysis and comparisonof present main PMD compensation techniques. The last we discussed several compensation methods in WDM system and note simultaneous multi-channel PMD equalization that will be the main method in the future.