The Numerical Study Of Propagation Characteristics And Interaction Of Soliton Pulses In The Single Mode Fiber

On the theoretic basis that soliton pulse propagation meets the nonlinear Schrodinger equation(NLS) in fiber, the paper obtained the numerical solutions of NLS and the high order nonlinear Schrodinger equation(HONLS).The propagation characteristics of the single pulse and the interaction of the double pulses have been studied in detail by changing the initial inputs of the pulses. Especially the interaction of the ultra-short pulses when the high order effects(self-frequency shift, self-steeping, the third order dispersion) are considered, some new results are obtained. In the paper, some detailed descriptions to the calculated results are given, at the same time, the good theory explanations are following. The studies will give a hard basis for the improvements of the communication quality and capacity of the soliton pulses.the mainly contents of the paper are:1. The propagation of the single pulse in fiber. When the initial input width of the single pulse above the scale of ps(lps=10"12s), the pulse propagation meets the NLS in fiber. With the differences of the pulse initial inputs, the pulse exhibits the periodical law but for the base soliton pulse. When its width below the ps, the propagation law meets HONLS and the high order effects can not be neglected, this will lead that pulse periodicity and symmetry are destroyed, the center position is shifted and the shape of the pulse is distorted. A simple summary to the propagation characteristics of the single pulse is given in the first part of this paper.2. The double pulses in the scale of ps propagate in fiber. When the initial input widths of the double pulses are in the scale of ps and their initial input intensities are same, they exhibit periodical variation and have an attraction between the pulses. There is not energy exchanged that it is a "completely elastic collision". When the two pulses have the different phase and energy each other, the pulses periodicities will disappear. In the different initial condition, there are a repulsion and a energy exchange between the pulses. The theoretic results approve that the things have a restraint to the interaction of the pulses to a certain extent.3. The double pulses in the scale of fs(1 fs=10-15) propagate in fiber. When the pulsesinitial input widths are in the scale of fs, their propagation laws meet the HONLS. In the things that the different phases and high order effects are considered, the pulses have not symmetries and the center positions produce a offset, at the same time, there is a very strong interaction each other. The results of the interactions exhibit the forms and the laws are different to the different high order effects. The pulses produce a splitting in the propagation and the splitting pulses also have a strong interaction. Sometimes the interactions lead to a strong intervention peak while sometimes there is no interaction between the pulses, and they keep independency respectively.4. Finally a summary and prospect are given. On the base of the theoretic basis and the results, a simple illumination is listed to the following work, which is very important to the control of the interaction between the pulses and the improvements of the quality and capacity in soliton pulse communication.