相干光正交频分复用(COOFDM)是目前光传输领域的研究热点之一。COOFDM系统采用马赫-曾德尔光调制器(MZM)实现射频(RF)信号到光的转换,而正交频分复用(OFDM)信号对非线性十分敏感,所以在系统设计上最关键的就是实现信号的线性传输。从理论上分析了COOFDM系统中MZM对OFDM信号的非线性影响,通过对MZM偏置点及调制指数优化,实现COOFDM系统的最佳传输,同时对COOFDM系统品质因子Q与偏置点及调制指数关系进行了仿真。结果表明,为了实现最佳线性传输,不同于传统的基于强度调制/直接检测系统(偏置点选在积分点),COOFDM系统中MZM最佳偏置点选在零点;MZM调制指数的选择也会对系统性能产生影响,当COOFDM系统中MZM调制指数为0 dB时,系统性能达到最佳。 Coherent Optical Orthogonal Frequency Division Multiplexing (COOFDM) is one of the hot topics in the field of optical transmission. The COOFDM system uses a Mach-Zehnder optical modulator (MZM) to convert radio frequency (RF) signals to light, whereas Orthogonal Frequency Division Multiplexing (OFDM) signals are very non-linear, so the key to system design is Realize the signal linear transmission. The influence of MZM on OFDM signal in COOFDM system is theoretically analyzed. By optimizing the MZM bias point and modulation index, the COOFDM system can be optimally transmitted. At the same time, the quality factor Q and bias point and modulation index The relationship was simulated. The results show that, in order to achieve the best linear transmission, different from the traditional intensity-based modulation / direct detection system (the bias point is selected at the integration point), the optimal MZM bias point in COOFDM system is selected at zero point. The system performance will be affected. When the MZM modulation index in COOFDM system is 0 dB, the system performance will be optimized.