为了使相干接收机输出的两路信号相位正交, 正确地解调信号, 采用施密特正交化算法对两路信号进行了理论分析和实验验证, 经正交失衡算法补偿后, 星座图的性能得到改善; 通过松尾环实现载频的跟踪、捕获以达到载波恢复, 实现了基带信号正确解调。结果表明, 经施密特正交化算法补偿后, 旋转的星座图得到了修正, 星座点间的欧几里德距离不相等问题得到修正, 基带信号畸变得到了改善; 当频偏在-300kHz~300kHz范围内, 松尾环可以实现载频的跟踪、捕获, 基带信号实现正确解调。该方案实现复杂度低, 切实可行, 适用于相干光通信系统的研究。

In order to make the received two signals orthogonal to each other and correctly demodulate the signal, Schmitt orthogonalization algorithm was used to theoretically analyze and experimentally verify the two signals. The performance of constellation was improved after orthogonal imbalance compensation. The carrier frequency was tracked and captured by the loose tail ring to achieve carrier recovery, and the baseband signal was demodulated correctly. The experimental results show that, after compensation by Schmidt orthogonalization algorithm, the rotated constellation is corrected and the problem of unequal Euclidean distance between constellation points is improved. The baseband signal distortion becomes corrected. When the frequency offset is in the range of -300kHz~300kHz, the loose tail loop can track and capture carrier frequency and baseband signal can be correctly demodulated. The scheme is low complexity and practical, and is suitable for the study of coherent optical communication systems.