为全面分析同向抽运光纤拉曼放大器的阈值特性，基于耦合微分方程，采用龙格库塔算法，数值模拟同向抽运光纤拉曼放大器中信号光功率沿光纤的演变过程，在此基础上根据实际情况推导出同向抽运光纤拉曼放大器的阈值公式。然后，数值计算各个参数对同向抽运光纤拉曼放大器阈值特性的影响，结果表明，初始信号光功率、光纤有效长度、拉曼增益系数、抽运光和信号光频率比值增加，阈值减小；光纤有效面积越大，阈值越大。

In order to analyze the threshold characteristics of forward- pumped fiber Raman amplifier (FRA), signal power distribution along a fiber for forward- pumped FRA is provided with Runge- Kutta method based on the coupling equations. Then, the theoretical expression of forward- pumped FRA′ s threshold is obtained with considering the practical factors, and the effects of these parameters on threshold of FRA are investigated detailedly. It is found that: the threshold will decrease when the initial signal power, the effective fiber length, Raman gain coefficient or the pump and signal frequency ratio increase, and the threshold will increase when the fiber efficient area increases.