五阶非线性光纤中高阶孤子的压缩特性研究

Investigation on pulse compression of high-order solitons in optical fibers with quintic nonlinearity

从光纤中包含五阶非线性的扩展非线性薛定谔方程出发,采用分步傅立叶算法,数值模拟了不同正五阶非线性参数下五阶和七阶孤子在两个孤子周期内的波形演化。结果表明,与没有五阶非线性时高阶孤子能够每经历一个孤子周期就能重现自身波形的规律不同,正五阶非线性可使五阶和七阶孤子获得压缩,脉冲的最大归一化强度随距离先增大,再振荡式变化。相比较而言,五阶孤子的脉冲峰值更大些,且受五阶非线性参数的影响更大。在压缩的脉冲主峰两边存在对称的弱旁瓣,且随着距离增加,旁瓣将互相排斥而远离中心。旁瓣数目及旁瓣的形状和位置随距离的演化特点与孤子阶数和正五阶非线性参数有关。对相关高阶孤子的频谱演化也作了数值计算和讨论。

Using the extended nonlinear Schro¨dinger equations including quintic nonlinearity in optical fibers and the split-step Fourier algorithm,the shape evolution of the fifth-and seventh-order solitons with propagating distance within two soliton periods is numerically simulated for different parameters of positive quintic nonlinearity.The results show that,different from the case without quintic nonlinearity,where the shapes of high-order solitons can recur after propagating every soliton period,the quintic nonlinearity can compress the fifth-and seventh-order solitons.The maximum normalized intensity of the pulse will increase with the distance before oscillating.In comparison,the peak intensity of the fifth-order soliton is larger and easier to be affected by the parameter of quintic nonlinearity.The symmetrical weak sidebands exist at the two sides of the main peak of the compressed pulse.With the increase of the distance,the sidebands will repulse with each other and go far away from the pulse center.The number of the sidebands and the sidebands evolution in terms of their shapes and position with the distance are related to the order of the soliton and the parameter of quintic nonlinearity.The corresponding spectral evolutionis of high-order solitons are also numerically calculated and discussed.