五阶非线性下零色散附近的调制不稳定性

Modulational Instability in the Region of Minimum Group-velocity Dispersion with Quintic Nonlinearity

在同时考虑光纤损耗、高阶色散以及高阶非线性情况下,从广义非线性薛定谔方程出发,研究了零色散附近的调制不稳定性,分析了四阶色散和五阶非线性对增益谱的影响.结果表明:当光脉冲工作在零色散附近时,四阶色散对调制不稳定性起决定作用,它使反常色散区的增益谱变宽.在光纤正常色散区,正(负)五阶非线性使增益谱的谱宽和峰值增大(减小);但在反常色散区,五阶非线性仅改变增益谱的峰值,几乎不影响谱宽.

Taking into account fiber loss, high-order dispersion and high-order nonlinearity, the modulation instability in the region of minimum group-velocity dispersion is investigated based on the extended nonlinear Schroedinger equation. The effects of fourth-order dispersion and quintic nonlinearity to the gain spectra are analyzed. The results show that the fourth-order dispersion, which increases the width of the gain spectra in the anomalous dispersion regime, dominates the modulation instability when the secondorder dispersion approaches the minimum value at the so-called zero dispersion wavelength. In the normal dispersion regime of fiber, the positive （negative） quintic nonlinearity will make the width and the peak value of the gain spectra larger （smaller）. But in the anomalous dispersion regime, the quintic nonlinearity only changes the peak value of the gain spectra and almost does not influence the width of the gain spectra.