为抑制低重复频率高能脉冲光纤主振荡功率放大(MOPA)系统的放大自发辐射(ASE)效应, 达到脉冲泵浦的最佳放大效果, 需要对泵浦脉宽进行优化。基于求解速率方程和功率传输方程, 理论研究了脉冲泵浦下掺镱光纤放大器上能级粒子数密度、光纤内存储能量、正反向放大自发辐射的瞬态响应。在给定的泵浦功率、光纤长度、纤芯面积和掺杂数密度等参数下, 数值计算得到的优化泵浦脉宽为793 μs。此外, 实验测定了ASE的建立时间；通过调节泵浦脉宽, 测定了脉冲泵浦下掺镱光纤放大器的放大效果, 实验中得到的泵浦脉宽的优化值为800 μs, 证明了数值模拟的正确性。

In order to suppress the amplified spontaneous emission (ASE) in the low-repetition rate high-energy fiber master-oscillator-power-amplifier (MOPA) system and achieve the best amplification results, it is necessary to optimize the pump pulse width. Based on solving a set of time-dependent rate and power transfer equations, the transient response of the upper level population distribution, stored energy and ASE of the Yb-doped fiber amplifier under pulsed pump are numerically studied. And the numerical optimum pump pulse width is 793 μs under specific parameters given in the paper, including the pump power, fiber length, core area, Yb-doped concentration, etc. In the experiment the ASE built-up time is measured, and the optimum value is 800 μs which is found by tuning the width of the pump pulse and measuring the amplification results of the fiber amplifier. The experiment shows the validity of the numerical simulation.