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从五阶感应电极化强度出发,导出了有损耗单模光纤中同偏振、不同波长的两光波交叉相位调制情况下的五阶非线性折射率;在同时考虑三、五阶非线性的情况下,推导了两光波的慢变振幅满足的耦合非线性薛定谔方程组,并进一步得出了线性化后微扰满足的方程组。分析了三、五阶非线性共存时的交叉相位调制不稳定条件和增益谱。结果表明,与只有三阶非线性的情形相比,在三、五阶非线性共存时,正五阶非线性加强调制不稳定性,使增益谱变宽,峰值变大,负五阶非线性则减弱调制不稳定性;和只有三阶非线性的情况类似,损耗也会使不稳定增益谱的谱宽变窄,谱峰减小;两光波扰动频率的大小关系会影响不稳定增益谱的谱宽、峰值和形状。
Based on the fifth-order induced polarization, we derive the fifth-order nonlinear refractive index of two light waves with the same polarization and different wavelengths in a lossy single-mode fiber. In the case of considering the third-order and the fifth-order nonlinearity , The coupled nonlinear Schrödinger equation for the slowly varying amplitude of the two light waves is deduced and the equations for the perturbation to be satisfied after linearization are obtained. The instability conditions and gain spectrum of cross-phase modulation are analyzed when the third and fifth order nonlinear coexist. The results show that, in the case of coexistence of third and fifth order nonlinearity, positive fifth-order nonlinearity enhances the modulation instability, widens the gain spectrum, increases the peak value, and negatively fifth-order nonlinearity Then the modulation instability is weakened. As with the third-order nonlinearity, the loss also narrows the spectral width of the unstable gain spectrum and reduces the spectral peak. The relationship between the two light-wave disturbance frequencies affects the unstable gain spectrum Spectral width, peak and shape.