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卫星相干光通信在国外已经接近工程应用阶段,主流的传输接收方式为BPSK调制/零差探测,接收端用光锁相环(OPLL)进行载波恢复。但即使在今天,光锁相环的实现依然有难度,而且存在捕获时间过长等现象。文中借鉴了现在的研究热点技术——光纤通信中的频偏估计、载波相位恢复技术,针对星间激光通信中存在GHz量级大多普勒频移的工程背景,提出了一种基于DSP的频偏开环补偿算法。从理论上分析了该算法的原理,重点研究了激光器噪声和接收机噪声对频偏估计精度带来的影响,并通过仿真进行了验证。本振光功率为10 d Bm时,当接收功率高于-47 d Bm,误码率优于10-4;将接收功率提高10 d B后,频偏估计标准差小于370 k Hz。
Satellite-related optical communications in foreign countries have been close to the engineering application stage, the mainstream transmission and reception mode for the BPSK modulation / homodyne detection, the receiving end with optical phase-locked loop (OPLL) carrier recovery. But even today, the realization of optical phase-locked loop is still difficult, and there are phenomena such as the capture time is too long. This paper draws on the current research hotspot technology - frequency offset estimation in optical fiber communication, carrier phase recovery technology, aiming at the background of gigantic doppler frequency shift in interstellar laser communication, proposes a DSP-based frequency Offset loop compensation algorithm. The principle of this algorithm is theoretically analyzed, and the influence of laser noise and receiver noise on the estimation accuracy of frequency offset is studied emphatically. The simulation is validated. When the local optical power is 10 d Bm, the error rate is better than 10-4 when the received power is higher than -47 d Bm, and the standard deviation of frequency offset estimation is less than 370 k Hz when the received power is increased by 10 d B.