为了实现卫星光通信系统从直接探测到相干探测的升级, 本文提出了一种基于空间光到光纤混频器耦合和判决驱动锁相环的升级方案。由于指向误差会引起光纤混频器的耦合功率损耗, 因此本文将针对发射端和接收端指向误差对判决驱动锁相环最优带宽的影响进行了理论研究和仿真分析。结果表明, 判决驱动锁相环最优带宽随收发两端指向误差增加而减小, 相应的最小相位误差则随收发两端指向误差增加而增加, 两者对接收端指向误差更为敏感。

In order to upgrade the communication system from direct detection to coherent detection, an upgrade scheme is proposed by using optical coupling from space to fiber hybrid and Decision Driven Phase Locked Loop (DDPLL). The pointing error would cause coupling loss and then influence the optimal bandwidth of DDPLL. Therefore, the theoretical analysis about the optimal bandwidth of DDPLL and simulation are carried out with considering the pointing errors of transmitter and receiver. The results shows that the optimal bandwidth of DDPLL decreases with pointing errors of transmitter and receiver, and the minimum phase error increases with pointing errors of transmitter and receiver. Both of these parameters are more sensitive to the receiver pointing errors.