在拉曼效应和参量放大共同作用下, 当激光脉冲在双折射光纤中传输时,根据所遵循的耦合模方程, 通过引入平行拉曼增益的洛伦兹模型, 导出了当输入泵浦波偏振方向同双折射轴成45°角时, 在双折射色散阶跃光纤中拉曼效应和参量放大共同作用所导致的增益, 讨论并分析了在不同色散区增益谱随相关参量的变化。结果表明: 由于拉曼效应、参量放大、双折射和色散的相互作用, 导致增益谱的斯托克斯波与反斯托克斯波彼此不对称; 在反常色散区, 产生的增益以反斯托克斯波为主, 在正常色散区则以斯托克斯波为主; 当表征距离的级数m发生变化时, 增益谱也随之发生变化, 可以利用色散阶跃光纤在适当的级数m位置提取T频率脉冲。

According to the coherently coupled nonlinear Schrodinger (NLS) equation of the propagation of a light pulse in birefringent fiber when Raman effect and parametric amplification together action, the Lorentzian model of parallel Raman gain spectrum is introduced. The gain is obtained combining Raman effect and parametric amplification when the pump wave polarization is oriented at 45°between the birefringent fiber axes in birefringent step-wise decreasing fiber. The gain spectrum is discussed as function of the input parameters in different dispersion regimes. The result shows that Stokes and anti-Stokes gain spectrum are asymmetric due to the interaction among Raman effect, parametric amplification, birefringent and chromatic dispersion. The gain appears as primarily anti-Stokes in anomalous dispersion regime, and Stokes in normal dispersion regime. The gain spectrum will change with token distance series m.The birefringent step-wise dispersion fiber is utilized, the T-frequency pulses can be extracted in distance series m of propriety.