基于科斯塔斯(COSTAS)光学锁相环路载波恢复进行建模分析,得到系统的闭环传递函数、误差函数及需要恢复的载波信号;设计系统采用复合控制,内环借助声光移频器实现快速、小范围跟踪,外环通过环路直接控制激光器拉进快捕带;为了得到良好的载波恢复和信号解调,设计基于异或门的COSTAS环鉴相模块对鉴相器进行分析,实现鉴相范围为[-42°,42°],鉴相增益为14.4 mV/(°) ,在环路带宽为1.5 MHz时,搭建实验进行测试。实验结果表明在码速率5 Gb/s时,载波恢复、信号解调良好,信号光功率为-40.4 dBm时,误码率为1.55×10 ^-8,随着速率的提高或降低,系统性能虽有下降,但仍能恢复载波信号并解调数据,为零差相干通信实验室验证提供了参考。

By modeling and analyzing on the carrier recovery based on COSTAS optical phase locked loop, we obtain the closed-loop transfer function, error function and carrier signal that to be recovered of the system. Then we design composite control to realize the fast and small range tracking by using the acousto optic frequency shifter in the inner ring, and quickly pull into capture tape by control laser in the outer ring. In order to get the good carrier recovery and signal demodulation, we design the phase detection module based on exclusive-OR gate (XOR) to analyze the phase detector. The phase detection ranges from -42 ° to +42 °, and phase detector gain achieves 14.4 mV/(°) when the loop bandwidth is 1.5 MHz. The experimental results show and that the carrier recovery and signal demodulation is good when the code rate is 5 Gb/s, and the error rate is 1.55×10 -8 when the signal power reaches -40.4 dBm. With the rate increasing or decreasing, the system performance decreases, but the system can recover the carrier signal and demodulate the data. This system can provide references for homodyne coherent communication laboratory verification.