对观察到的正色散腔被动锁模掺铒光纤激光器的实验现象进行了理论分析。采用Master方程对被动锁模脉冲的静态特性进行数值模拟, 结果显示正色散腔可以满足稳定性条件, 能够获得稳定的被动锁模脉冲, 并且正色散腔内的脉冲具有很强的啁啾特性。根据耦合非线性薛定谔方程, 对正色散腔内稳定脉冲的动态形成过程进行模拟, 初始的宽时域小信号经过在腔内多次运转后逐渐被放大并压窄, 最终形成稳定的锁模脉冲。对在该腔内观察到的多脉冲共存现象进行分析, 结果表明多脉冲共存是由于脉冲峰值功率的增加受到腔内功率透过率的限制所致, 并对多脉冲在腔内的演变过程进行数值模拟, 其结果与实验相吻合。

The experimental results observed in passively mode-locked Er-doped fiber laser with positive dispersion are analyzed theoretically. The static pulse characteristics are simulated numerically according to Master equation, and the conclusion is that stable passively mode-locked pulse with large chirp will be obtained in the cavity with positive dispersion. The evolvement process of pulse is simulated by coupled nonlinear Schrdinger equations, and the original small signal with large time-width evolves to stable mode-locked pulse after some cycles. The multiple-pulse operation observed in this laser is analyzed, and the results display that the multiple-pulse is caused by peak power limiting. The multiple-pulse operation evolvement is simulated, and the same results with experiments was obtained.