饱和非线性光纤正色散区的交叉相位调制不稳定性

Modulation Instability Induced by Cross-Phase Modulation in the Normal Dispersion Region of Fibers with Saturable Nonlinearity

在考虑到光纤饱和非线性效应的情况下,给出了同偏振、不同波长的两光波的慢变振幅满足的耦合非线性薛定谔方程组以及线性化后微扰满足的方程组。在光纤的正色散区,分析并讨论了交叉相位调制不稳定增益谱随两光波输入功率变化的规律。结果表明,与饱和非线性光纤中自相位调制不稳定性的增益谱类似,交叉相位调制不稳定增益谱的临界扰动频率、峰值增益大小随两光波输入功率的增大也呈现出先增大后减小的特点,而二者随两光波输入功率变化的快慢都与两扰动的频率大小有关,即会出现两个不同的输入功率对应同一个不稳定增益峰值和临界扰动频率的情形。

Taking into account the saturable nonlineary of the optical fibers, the coulped nonlinear Schrodinger equations of the slowly varying envelopes for two optical waves of different frequencies with the same polarizations, and the linearized nonlinear Schrodinger equations for the perturbations are given. In the normal dispersion region of optical fibers, the variation law of the gain spectra of modulation instability induced by cross-phase modulation with the input powers of the two waves is analyzed and discussed. The results indicate that, similar to that of the gain spectra of self-phase modulation induced modulation instability in optical fibers with saturable nonlinearity, the critical perturbation frequency as well as the peak gain of cross-phase modulation induced modulation instability also increases with the input powers before decrease. The varying velocity of the two parameters is related to the perturbation frequencies. This may lead to a unique value of peak gain and critical perturbation frequency for two different input powers.