中文摘要：

从非线性薛定谔方程出发，对SPM作用引起传输脉冲的相位作了合理近似，引入了频谱展宽因子，发现在存在增益时正色散光纤的SPM作用加剧了脉冲频谱展宽幅度，并且脉冲中心和两翼部分的频谱展宽差异很大．给出了存在增益的正色散光纤中高斯型脉冲自相似传输的时域演化，揭示了脉冲展宽的中心部分对边翼部分挤压和覆盖及最终形成自相似脉冲的过程，提出了自相似传输现象的一种合理解释．并通过数值模拟三种不同形状初始脉冲的自相似演化过程对提出的理论进行了验证．

英文摘要：

The approximation of the phase introduced by self-phase modulation （SPM） is reasonably calculated and the spectrum broadening factor is given basing on nonlinear Schrodinger equation. The spectrum of propagating pulses is broadened seriously by SPM in the fiber with normal group velocity dispersion （GVD） when gain （G） exists. And the spectra broadening of the central part of pulses is quite different from that of the wings of the pulses. The self-similar evolution of Gaussian pulses is described. The temporal shape of the wings of the pulses being covered by the central part gradually is discovered. A theoretical explanation of self-similar pulses propagation is given which verified by the numerical simulation for the self-similar evolution of three kinds of pulses.