Polarization Mode Dispersion In Optical Soliton Communication Systems

Fiber communication has become the main body of modern communication system with its high transmission speed, long transmission distance, large information capacity and strong security characteristics. As the communication technology progresses, a new kind of nonlinear all-optical communication technology——soliton communication which has super high speed ,large capacity, super long distance comes into our sight .Soliton communication can reach a number of ten thousand kilometers communication distance by overcoming the optical transmission distance limit duo to dispersion. It also suits WDM and OTDM, so that it is the best way to improve the capacity of Optical fiber communication system. At the same time, the capacity limit duo to PMD is more and more serious and become one of the important factors that limit our high speed transmission system.We introduce a new dispersion management method of realizing exponentially decreasing dispersion fiber by using only two kinds of segments of fibers with different dispersions connected together. Different average dispersion values can be realized by changing the lengths of two fibers in every dispersion map. Exponentially decreasing dispersion fiber is used to obtain the optimum soliton transmission situation.Picosecond soliton's property is verified by solving soliton's common transmission equation——nonlinear schrodinger equation(NLSE) with the usage of split-step fourier method. When the pulse width is below the picosecond order, high order nonlinear effect and high order dispersion effect can not be ignored, at the same time the transmission of the soliton with femtosecond order in fiber satisfies the high order modified nonlinear schrodinger equation(HONLS). Fetmosecond soliton's property is studied the same way with that of Picosecond soliton.Based on large amount of researches about picosecond order soliton's PMD up to now, fetmosecond soliton system's property is investigated by solving the picosecond soliton couple equations which contain PMD——the coupled high order modified nonlinear schrodinger equation. The discussions about homophase and orthogonal femtosecond soliton show that orthogonal femtosecond soliton has better self-trapping characteristic than homophase femtosecond soliton; polarization angle has no effect on self-trapping; the larger the birefringence coefficient is, the less obvious the self-trapping effect is; homophase and orthogonal soliton are both sensitive to relative magnitude; input power has threshold value on orthogonal soliton couple; it is difficulty for homophase femtosecond soliton to get the self-trapping effect. In the end, we discuss a means to determinant the threshold value of input power in two orthogonal femtosecond solitons.