鉴于相干光正交频分复用系统(CO-OFDM)易受非线性效应影响, 严重制约系统传输性能, 提出一种基于星座恢复的降低系统峰均值功率比(PAPR)的方法。对系统模型及作用机理进行分析, 仿真结果显示, 以10 Gbit/s的速率通过单模光纤传输720 km, 基于星座恢复的CO-OFDM系统Q值较无非线性抑制的CO-OFDM系统有3 dB提高; 另外, 系统最佳限幅比例系数受色度色散影响, 随着色散因子的增大, 星座恢复效果也逐渐减弱, 在传输240 km条件下, 色散因子为12 ps/nm·km较6 ps/nm·km, 限幅比例系数从0.9降低至0.8。

Coherent optical orthogonal frequency division multiplexing (CO-OFDM) system is sensitive to nonlinearity because of high peak-to-average power ratio (PAPR) and closely-packed subcarriers, which seriously suppresses the transmission performance.A method for reducing the PAPR was put forward based on constellation restoration, the system model and action mechanism were analyzed. Analyses and simulation results show that, the system Q value of constellation restoration based CO-OFDM system is improved by about 3 dB for 720 km distance at a speed of 10 Gbit/s transmission through standard-single-mode fiber (SSMF),compared with the CO-OFDM system without nonlinearity suppression. Meanwhile, the clipping factor is strongly influenced by the chromatic dispersion which can decrease the effect of constellation restoration. At the length of 240 km, the clipping factor is 0.9 and 0.8, while the dispersion factor is 12 ps/nm·km and 6 ps/nm·km,respectively.