色散渐减光纤中自相似脉冲传输区域的研究

从非线性薛定谔(NLS)方程出发,用分步傅里叶方法结合对数值解的波形分析,确定了色散渐减光纤(DDF)中能实现自相似脉冲传输的区域,并研究了初始脉冲和光纤参数对自相似区域和演化速度的影响。结果表明,初始脉冲能量的减小有利于扩宽自相似区域,但会使自相似演化进程略为减慢;初始脉宽有一个最佳值,在最佳值上自相似区域最宽,演化较快且输出脉冲和啁啾较为稳定;高斯脉冲比双曲正割脉冲更快转化为自相似脉冲,传输区域也更广。选择具有较小非线性参量的DDF可以获得较广的自相似区域,同时非线性参量的增大可以加快自相似演化,而群速度色散参量和增益系数必须选择在最佳值附近,才能获得最大自相似区域和最快演化速度。

Research of Self-Similar Region in a Dispersion-Decreasing Fiber

Based on nonlinear Schrodinger (NLS) equation, self-similar region in which pulses can propagate with a parabolic intensity profile in dispersion-decreasing fiber (DDF) is established by split-step Fourier method and waveform analysis, influences of initial pulse and fiber parameters on self-similar region and the speed of evolution are also investigated. Results show that reduction of initial pulse energy can expand self-similar region but slow down the self-similar evolution. Initial pulse width has an optimum value with the widest self-similar region and relatively high evolution speed. Input pulses with Gaussian profile have a faster evolution speed and a wider self-similar region than those with hyperbolic secant profile. To get an extensive region for self-similar propagation, a DDF with smaller nonlinearity parameter can be used, and the increase of nonlinearity parameter can speed up self-similar evolution. In addition, group-velocity dispersion parameter and gain coefficient should be set at its optimum value to get the largest self-similar region and the fastest evolution speed.