Theory Analysis And Compensation Of Polarization Mode Dispersion In High Speed Optical Fiber Communication System

In high-speed optical fiber communications systems, with the development of Erbium Doped Fiber Amplifier and Non-zero Dispersion Shifted Fiber, the effects of chromatic dispersion, attenuation and nonlinearity on performance of Optical fiber communications system are minimized. Polarization mode dispersion has been becoming the new restriction problem for the development of transmission systems. Polarization mode dispersion is caused by the birefringence phenomenon in optical fiber. It will broaden the optical signal pulse, worse the inter-symbol interference and increase the bit error rate in receiving systems. Polarization dependence loss will always existent in optical fiber. Polarization dependence loss not only affects the power of transmission signals, but also changes the speciality of principal polarization state with polarization mode dispersion. That will affect the effect of polarization mode dispersion compensation. The topic of this thesis is focused on the specialty of transmission systems base on the impacts of polarization mode dispersion and polarization dependence loss, and the technology of polarization mode dispersion compensation.Firstly, the paper does a summary of the relating fundamental theories of polarization mode dispersion. It includes the cause of formation, math description, definition, statistical characteristic and measurement technology.Secondly, this paper educes the expression of root mean square pulse width base on the impacts of polarization mode dispersion, and the expression of root mean square pulse width base on the impacts of polarization mode dispersion and polarization dependence loss. Base on the model of one polarization dependence loss element sandwiched between two fibers with polarization mode dispersion, this paper educes the expression of polarization mode dispersion vector and differential group delay. It also researches the principal polarization states and intensity of transmission signal with the impacts of polarization mode dispersion and polarization dependence loss. And analyzes the first- and second-order polarization mode dispersion with the impacts of polarization mode dispersion by numerical simulation .Finally, the paper introduces the structures and principle of main composing part in polarization mode dispersion adaptive compensation system. It includes the design of polarization mode dispersion simulator, the obtaining of degree of polarization and the work principle of polarization controller. By analyzing the compensation principle of first- and second-order polarization mode dispersion, this paper research a second-order polarization mode dispersion adaptive compensation algorithm, which could automatic adjust search step by tracking the degree of polarization of the feedback signal. The compensation algorithm could rapidly accomplish convergence, and avoid tracking into local extreme point. It also could eliminate instant worsening and noise interfering in transmission systems.