相干光OFDM在高速光传输中的应用

摘要

CO-OFDM (coherent optical orthogonal frequency division multiplexing system), with computation efficiency and ease channel estimation, could effectively suppress fiber CD (chromatic dispersion) and PMD (polarization-mode dispersion), and probably become the principal technology for future high-speed optical transmission. Based on optical transmission and OFDM theory, the system scheme of and the channel model for coherent optical OFDM system is are emphaticalyy analyzed. With such a scheme, numerical simulation is done to validate the bias point of the optical modulator and channel estimation algorithm. Analysis and simulation results show that the optical OFDM could effectively suppress fiber chromatic dispersion without any online dispersion compensation. The received signal could be recovered effectively with channel (phase) estimation and equalization. Simulation also indicates that with optimal modulator bias point for the CO-OFDM system at zero point, the system Q value could be improved about 10dB as compared with traditional intensity-modulation/direct-detected system.%　　相干光正交频分复用系统(CO-OFDM,Coherent Optical Orthogonal Frequency Division Multiplexing)可有效抑制光纤色度色散和偏振模色散,有望成为解决未来高速光传输的主流方案。这里结合光传输理论及正交频分复用系统(OFDM,Orthogonal Frequency Division Multiplex)技术原理,对CO-OFDM系统方案实现及信道等效模型进行了分析,通过数字仿真验证系统光调制器偏置点选择及信号均衡算法。理论分析和仿真结果表明,CO-OFDM系统采用单抽头频域均衡,可有效抑制光纤色散效应。光调制器偏置点选择在零点,可实现系统对OFDM信号的最佳线性调制,与传统强度调制/直接检测(IM/DD)系统比较,CO-OFDM系统品质因子有10 dB提高。