色散非管理n-PSK相干光通信系统载波相位恢复的解析研究
Analytical Investigations on Carrier Phase Recovery in Dispersion-Unmanaged n-PSK Coherent Optical Communication Systems
摘要：
利用相干光检测和数字信号处理技术，采用前馈和反馈载波相位恢复方法，可以有效地抑制激光相位噪声和均衡增强相位噪声。本文对长距离高速n-PSK（n-PSK）光纤通信系统中的反馈和前馈载波相位恢复方法进行了理论分析，包括单抽头归一化最小均方（LMS）算法、分块平均算法和维特比-维特比算法。在考虑激光相位噪声和均衡增强相位噪声的情况下，给出了n-PSK相干光传输系统中估计载波相位和预测误码率性能（如误码率本底）的解析表达式，并进行了讨论。结果表明，在相位噪声方差（或有效相位噪声方差）较小的情况下，维特比-维特比载波相位恢复算法优于单抽头归一化LMS算法和块平均算法;在相位噪声方差（或有效相位噪声方差）较大的情况下，单抽头归一化LMS算法优于其他两种算法。此外，单抽头归一化LMS算法对调制格式的电平更敏感。
英文摘要：
Using coherent optical detection and digital signal processing, laser phase noise and equalization enhanced phase noise can be effectively mitigated using the feed-forward and feed-back carrier phase recovery approaches. In this paper, theoretical analyses of feed-back and feed-forward carrier phase recovery methods have been carried out in the long-haul high-speed n-level phase shift keying (n-PSK) optical fiber communication systems, involving a one-tap normalized least-mean-square (LMS) algorithm, a block-wise average algorithm, and a Viterbi-Viterbi algorithm. The analytical expressions for evaluating the estimated carrier phase and for predicting the bit-error-rate (BER) performance (such as the BER floors) have been presented and discussed in the n-PSK coherent optical transmission systems by considering both the laser phase noise and the equalization enhanced phase noise. The results indicate that the Viterbi-Viterbi carrier phase recovery algorithm outperforms the one-tap normalized LMS and the block-wise average algorithms for small phase noise variance (or effective phase noise variance), while the one-tap normalized LMS algorithm shows a better performance than the other two algorithms for large phase noise variance (or effective phase noise variance). In addition, the one-tap normalized LMS algorithm is more sensitive to the level of modulation formats.
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