通过分步傅里叶算法对光纤传输模型——非线性薛定谔方程进行求解，研究光纤的色散和非线性对新型闭环双向三激光器混沌保密通信系统的影响。分析了在色散、非线性以及色散和非线性共同作用下，光纤传输距离对混沌信号和解调信息质量的影响。结果表明：随着传输距离增加，色散导致混沌信号展宽，展宽比率也随之增大；混沌信号同步性逐渐变差，导致解调信息质量变差。非线性不影响混沌信号的时域波形，但非线性与色散的共同作用，导致混沌信号迅速变化，混沌信号同步性迅速变差，使解调信息质量急剧恶化。

The optical fiber transmission model, i.e., the nonlinear Schrodinger equation, is solved by split-step Fourier algorithm to research the effects of fiber-optical dispersion and nonlinearity on a new closed-loop dual-directionally chaotic secure communication system with three lasers. The effects of the actions of dispersion, nonlinearing, and combination action of dispersion and nonlinearity on the chaotic signal and the demodulated message quality are analyzed as the optical fiber transmission distance increases. The results show that: the dispersion leads to the broadening of chaotic signal, and the increase of broadening ratio, and reduces the synchronization performance of chaotic signal with the optical fiber transmission distance increasing, which results in the degradation of the demodulated message quality. Nonlinearity does not affect the time-domain waveform of chaotic signals, but the combination effects with dispersion make the chaotic signal change rapidly, as a result, the synchronization performance of chaotic signals varies rapidly, and the demodulated message quality sharply deteriorates.