Study Of The Transmission Characteristics Of Dark Soliton In Decreasing Dispersion Fibers

In1973, Hasegawa first proposed to take advantage of the dispersion to balance the fiber nonlinear in theory, and achieved the stable soliton transmission in fiber. Then the new area of optical soliton communication is opened to us. In1980, Mollenauer verified the possibility of optical soliton communication experimentally. The nonlinear Schrodinger (NLS) equation is used to describe the soliton transmission in different medium. Soliton transmission has wide application in optical communications, nonlinear optics, plasma physics, photonic crystals, Bose-Einstein condensation and many other research fields.In optical fiber communication, the decreasing dispersion fiber is a new specialty optical fiber, whose dispersion value is not a constant along the direction of the optical pulse propagation, but changes all the time. Thus the changing dispersion can offset the nonlinear effect. Because of the unique performance, the decreasing dispersion fiber is used widely in optical fiber communication.Since the influence of loss, dispersion and nonlinear effect, compared with the bright soliton, dark soliton has a lot of advantages, that bright soliton doesn’t have. The dark soliton has higher stability and self-recovery, at the same time, broadened slowly, subject less influence of various disturbances(such as Raman self-frequency shift). So dark soliton is considered as the better transmission carrier in optical fiber communication. Dark soliton with these advantages, has lots of potential applications in the optical fiber communication of long distance and the future communication. In this paper, the propagation characteristics of optical pulse in decreasing dispersion fiber is discussed with the theoretical model-variable coefficient nonlinear Schrodinger (vcNLS) equation. In this paper, with the aid of the Hirota method, the bilinear forms of the Schrodinger equation are derived. Basing on the bilinear form, the analytic dark soliton solutions for the nonlinear Schrodinger equation are obtained. Specifically, the work is outlined as follows:(1)Basing on the dark single soliton analytic solutions, the propagation properties of dark single soliton is studied. Then the loss, dispersion and nonlinearity are analyzed to know how these parameters influence the propagation of the dark soliton. Results of our research shows that propagation route of solitons can be effectively controlled by loss, dispersion and nonlinearity, which can improve the quality of signal transmission in optical communications.(2)In this paper, the process of solving dark double solitons solution is also obtained. Then the interaction of the dark double solitons is discussed. In addition, soliton control of the dark double solitons is achieved.The result might be benefit to the soliton control techniques in decreasing dispersion fiber.