由基本物理过程出发,导出了数字或模拟强度调制光通信系统中,包含光纤损耗、色散和自相位调制综合作用下的光功率频域传递函数,由此得到了任意功率波形在传输过程中的演化表达式及各项的物理意义.结果表明,自相位调制导致的功率变化在低频部分与调制频率的平方成正比,在高频部分则与调制频率的平方的正弦成正比.解析公式与数值模拟结果在小调制信号下相符得很好,特别适用于计算非线性效应对系统噪声的影响以及诸如双边带和单边带微波调制光通信系统等情况;在诸如非归零码的大调制信号下,本文公式仍能正确地表示传输后的波形,对系统设计和分析有指导意义.

A simple analytical optical power transfer function is derived in frequency domain for intensity modulation systems with fiber loss, chromatic dispersion and self-phase modulation. Expression to calculate the distortion of arbitrary optical power waveform is obtained with distinct physical meaning of each term. The results show that the induced power variation is proportional to the square of modulation frequency (SOMF) at low frequency region, while proportional to the sine of SOMF at high frequency region. The analytical result agrees well with numerical simulation under weak modulation and can correctly predict the time-domain waveform under strong modulation such as non-return-to-zero in intensity modulation/direct detection systems.