为解决传统拉曼放大器增益系数低和增益不平坦的问题, 采用级联光子晶体光纤的设计方法设计了一种增益平坦的拉曼光纤放大器.采用受激拉曼散射效应的稳态分析理论, 分析了光子晶体光纤的拉曼增益谱, 建立了拉曼放大器的理论模型.通过解耦合方程, 推导了实现增益平坦的约束条件, 发现光纤长度和泵浦功率是影响拉曼光纤放大器增益平坦度的两个参数.仿真结果表明, 在1 508~1 544 nm的带宽范围内, 实现了一个增益高达21 dB, 增益平坦度仅为0.14 dB的光子晶体拉曼光纤放大器, 可在光纤通信系统应用中发挥重要作用.

A gain-flattened Raman fiber amplifier was proposed by using the method of cascading photonic crystal fiber, which improves the Raman gain coefficient and reduces the gain flatness of the traditional Raman fiber amplifier. Based on steady-state analysis theory of the stimulated Raman scattering effect, the photonic crystal fiber Raman gain spectrum and established the theoretical model of this Raman amplifier were analyzed. Through solving the coupled equation, the constraint condition for realizing gain-flattened is deduced, showing that the fiber length and pump power are two parameters affecting gain flatness of Raman fiber amplifier. Numerical simulation results show that a photonic crystal Raman fiber amplifier with 21 dB high gain and only 0.14 dB gain flatness over the bandwidth range of 1 508 nm to 1 544 nm, can be obtained. It will play an important role in the design of high efficient optical fiber communication systems.