受激布里渊散射（SBS）效应是限制连续单频光纤激光最大输出功率的主要因素。为抑制增益光纤的SBS效应，通过改变增益光纤的掺杂浓度提出了一种展宽增益光纤的布里渊增益谱，降低布里渊增益系数，从而提高激光输出功率的方法。基于速率方程、热传导和布里渊增益谱计算模型，在增益光纤最高温度基本相同的情况下，对传统恒定掺杂和梯度掺杂方式下增益光纤中的热分布、激光器的输出功率和布里渊增益谱进行了数值模拟。结果表明：相比传统恒定掺杂光纤，设计的梯度掺杂增益光纤将布里渊增益谱展宽了1.2倍，布里渊增益系数降低了41%，SBS阈值功率提高了1.7倍，有效抑制了光纤的SBS效应；降低了增益光纤的熔点温度，提高了光纤激光器的稳定性。

Stimulated Brillouin scattering (SBS) effect is the main factor limiting the maximum output power of the continuous single frequency fiber laser. In order to suppress SBS effect in the gain fiber, a method is proposed which can broaden Brillouin gain spectrum, reduce Brillouin gain coefficient of the gain fiber, and thus improve the output power of the fiber laser by changing the doping concentration of the gain fiber. Based on the rate equation, thermal conduction and Brillouin gain spectrum calculation models, the thermal distribution of the gain fiber, the output power of laser and Brillouin gain spectrum are simulated under the conditions of constant and gradient doping when the maximum temperatures of the gain fibers are basically the same. Results show that, compared with the conventional constant doping fibers, the designed gradient doping gain fiber can broaden Brillouin gain spectrum by 1.2 times, reduce Brillouin gain coefficient by 41% and increase the SBS threshold power by 1.7 times, which suppresses the optical SBS effect effectively. The fusion point temperature of the gain fiber is reduced, and the stability of the fiber laser is improved.