保偏阶跃光纤中矢量调制不稳定性

利用光脉冲在非线性双折射光纤中传播时所遵守的相干耦合非线性薛定谔方程，研究了保偏色散阶跃光纤（SWDF）中偏振方向与双折射轴成任意角度时、在反常色散区和正常色散区所产生的调制不稳定性。结果表明：在反常色散区，对于任意的偏振角和任意输入功率的光脉冲都产生调制不稳定性；在正常区散区，存在不稳定区域和稳定区域，对应不同的不稳定区域输入临界功率不同，脉冲有不同的增益谱，给出了调制不稳定性增益谱随传输距离和偏振角的变化关系。

Vector Modulation Instability in Polarization-maintaining Step-wise Decreasing Fiber

The coherently coupled nonlinear Schrdinger(NLS) equation of the propagation of a light pulse in a birefringence nonlinear fiber has been utilized.We have studied modulation instability in polarization-maintaining step-wise decreasing fiber(SWDF) not only in anomalous dispersion regime but also in normal dispersion regime when the angle of the polarized direction and the birefringence axes is arbitrary.The results show that modulation instability can be produced when the angle of the polarized direction and the birefringence axes as well as input power is arbitrary in anomalous dispersion regime.There are both instability region and stability region in normal dispersion regime.The input pulses have different gain spectra at instability region and input power are different obviously.The relation between gain spectra of the modulation instability and the propagation distance and polarized angel has been given.