大线宽相干光正交频分复用系统中盲相位噪声补偿

基于大线宽相干光正交频分复用(CO-OFDM)系统, 提出了一种可以有效克服符号判决错误的盲载波间干扰(ICI)相位噪声补偿算法。使用该算法之前, 先使用无迭代盲(IFB)算法对公共相位误差(CPE)的相位噪声进行补偿。该算法采用了形式简单的代价函数, 可大幅减小计算复杂度。该ICI相位噪声补偿算法包括粗略ICI和精细ICI相位噪声补偿两个阶段, 先使用平均能量盲(Avg-BL)算法进行粗略ICI相位噪声补偿, 再使用公共相位误差分割补偿(CPEC)算法进行精细ICI相位噪声补偿。该CPEC算法对粗略ICI相位噪声补偿后的频域数据进行判决, 再将每个接收到的正交频分多路复用(OFDM)时域符号分割为一定数目的亚符号, 从而求出每个亚符号中相位噪声的近似平均值。Avg-BL算法有效解决了CPEC算法中的符号判决错误传播问题;CPEC算法在时域OFDM亚符号分割数目较大的情况下, 对ICI相位噪声具有较好的补偿效果。对50 Gbit/s CO-OFDM系统在传输距离为100 km的情况进行了仿真, 仿真结果表明, 与Avg-BL算法和CPEC算法等ICI相位噪声算法相比, 所提算法具有较好的相位噪声补偿效果, 且具有较高的频谱利用率。在该算法中, 选择合适的时域OFDM亚符号分割数目, 可取得较好的补偿效果, 且算法复杂度并未显著增加。

Abstract

A blind inter-carrier interference (ICI) phase noise compensation algorithm, which can solve the problem of symbol decision error effectively, is proposed based on the large linewidth coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. Before using the proposed algorithm, we use the non-iterative blind (IFB) algorithm to compensate phase noise of common phase error (CPE). The proposed algorithm uses the cost function which is with simple form, so the computational complexity reduces significantly. The ICI phase noise compensation algorithm includes coarse ICI phase noise compensation and fine ICI phase noise compensation. Firstly, the average-power blind (Avg-BL) algorithm is implemented in the coarse ICI phase noise compensation, and then the common phase error compensation (CPEC) algorithm is implemented in the fine ICI phase noise compensation. A decision process will be performed by CPEC algorithm for the frequency-domain signals after the coarse ICI phase noise compensation. Every received OFDM symbol is separated into several sub-symbols in time-domain, and the approximate average value of phase noise of every sub-symbol is calculated. The sign decision error propagation problem in CPEC algorithm is solved when we use the Avg-BL algorithm. When the number of sub-symbols separated from OFDM symbol in time-domain is large, the CPEC algorithm can achieve the desired compensation performance for ICI phase noise. For the 50 Gbit/s CO-OFDM system with 100 km transmission distance, the numerical simulation is performed. The simulation results show that, compared with the other phase noise compensation algorithms, such as the Avg-BL algorithm and the CPEC algorithm, the proposed algorithm has good phase noise compensation performance with high spectral efficiency. With the suitable number of OFDM sub-symbols in time-domain, the proposed algorithm can obtain better compensation performance, and its complexity does not increase significantly.

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任宏亮, 康少源, 卢瑾, 郭淑琴, 覃亚丽, 胡卫生. 大线宽相干光正交频分复用系统中盲相位噪声补偿[J]. 光学学报, 2017, 37(1): 0106005. Ren Hongliang, Kang Shaoyuan, Lu Jin, Guo Shuqin, Qin Yali, Hu Weisheng. Blind Phase Noise Compensation in Large Linewidth Coherent Optical Orthogonal Frequency Division Multiplexing Systems[J]. Acta Optica Sinica, 2017, 37(1): 0106005.

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