保偏光纤中相近频率传输区域的调制不稳定性

Modulation instability of near frequency propagation regime in polarization-maintaining fibers

利用激光脉冲在光纤中传播时所遵守的相干非线性薛定谔耦合方程,研究了保偏光纤中两相近频率的线偏振光,其偏振方向相互正交且平行于光纤的双折射轴,且偏振方向沿两个双折射轴的分量强度相等时,在同为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和正常色散区都能产生调制不稳定性;在正常色散区存在不同的调制不稳定性功率区域,对应不同的功率区域,导致增益谱表现出明显的不同,并且当输入功率一定时,波长差(或频率差)的变化导致增益谱的变化.

The coherently coupled nonlinear Schroedinger （NIS） equation of the propagation of a light pulse in a fiber has been utilized. We have studied modulation instability of linearly polarized lights with near frequency not only in anomalous dispersion regime but also in normal dispersion regime in polarization-maintaining fibers, when the polarization direction along the two birefringence axes are orthogonal and the intensities along the two birefringence axes are equal. The results show that modulation instability can be produced both in anomalous and normal dispersion regimes. The input pulses have obviously different gain spectra when input power regime is different in normal dispersion regime. Furthermore, the gain spectra are different for different wave lengths （or different frequencies） when the power of input pulse is kept constant.