4阶色散和5阶非线性下色散缓变光纤中的调制不稳定性

Modulation Instability with Fourth-order Dispersion and Quintic Nonlinearity in Dispersion-decreasing Fiber

基于包含4阶色散和5阶非线性的广义非线性薛定谔方程,研究了色散缓变光纤(DDF)中调制不稳定(MI)增益谱,分析了4阶色散、5阶非线性、入射光功率以及光纤色散纵向变化参量对增益谱的影响.结果表明,4阶色散不仅导致在正常色散区产生了MI,而且在反常色散区也出现了新的MI.正5阶非线性加强了MI,它使增益谱的谱宽和峰值增大,而负五阶非线性则对MI起抑制作用.入射光功率越强,5阶非线性对MI增益谱的影响越大,且光纤色散纵向变化参量越大,DDF中MI越明显.

The gain spectra of modulation instability （MI） in dispersion-decreasing fiber （DDF） are investigated based on extended nonlinear Sehr odinger equation considering fourth-order dispersion and quintic nonlinearity. The effects of fourth-order dispersion, quintic nonlinearity, incident optical power and axilly-varying dispersion parameter to the gain spectra are analyzed. Because of fourth-order dispersion, MI occurs in the nor： mal dispersion regime and a new spectrum region is produced in the anomalous dispersion regime. The positive quintie nonlinearity strengthens MI, which makes the width and the peak value of the gain spectrum larger. However, the negative quintic nonlinearity weakens MI. Furthermore, the spectral width increases with the increase of the incident optical power and the dispersion decaying factor.