自发辐射(ASE)是掺铒光纤放大器(EDFA)的重要噪声源，对于由EDFA构成的光纤激光器有重要影响。理论与实践证明，它与抽运方式紧密相关，所以研究脉冲抽运时掺铒光纤(EDF)的自发辐射有重要的学术价值。同时，脉冲抽运对于EDFA锁模激光器的研究也有一定意义。从理论和实验两方面研究了小信号脉冲抽运时，抽运脉冲宽度和幅度对于EDF的自发辐射特性的影响，得到了小信号抽运时输出ASE噪声平均值的近似解析解。研究发现，小信号脉冲抽运时输出信号的幅度与抽运脉冲的宽度成正比。这个新现象可用于脉冲宽度的全光检测。

The active spontaneous emission (ASE) is the important noise source for erbium-doped fiber amplifier (EDFA), affecting fiber laser based on the EDFA seriously. The theory and practice show that the ASE is closely related with pump methods, so the study on the ASE of erbium-doped fiber (EDF) under the condition of the pulse pumping has important scientific significance. What′s more, pulse pumping makes some sense to the mode-locked laser based on EDFA. The effects of pump pulse with different widths and amplitudes on the ASE are investigated by the theoretical and experimental methods. An approximate analytical solution of output ASE noise average is derived when pump signal is small. The results show that the output amplitude of ASE is proportional to the input width of pump pulse when the pump pulse is small. The new phenomena can be used for the all-optical measurement of a pulse width.