基于幅度比值的低复杂度频偏估计算法

针对在任意阶正交幅度调制(M-QAM)的相干光通信系统中发射激光器与本振激光器之间存在频率偏差的问题，提出了一种基于幅度比值的低复杂度频偏估计算法。该算法先对接收信号做快速傅里叶变换(FFT)，再利用所获得的离散谱中主峰值与次峰值的关系进行频率插值，从而对频偏进行精确估计，大幅减少了运算复杂度。仿真了算法在20 Gbaud 16QAM 的单偏振传输系统中的性能，并与梯度下降法(GD)和调频Z 变换(CZT)的频偏估计算法进行了对比，仿真结果显示，基于幅度比值的频偏估计算法性能不随被估计信号的频率分布而产生波动，而且与3次迭代的GD 算法和CZT算法精度相当，但硬件复杂度降低了约75%。

Abstract

A low comlexity frequency offset estimation algorithm based on amplitude ratio is proposed due to the frequency offset between transmitter laser and local oscillator (LO) laser in coherent optical M- ary quadrature amplitude modulation (M-QAM) systems. The proposed algorithm utilizes the relationship between the maximum amplitude and the second largest amplitude of the signal spectrum to estimate the frequency offset accurately, which reduces the computational complexity greatly. A coherent optical 20-Gbaud 16-QAM transmission system with single polarization is simulated to investigate the performance of the proposed estimator with respect to gradient descent(GD) and chirp Z- transform(CZT).The simulation results show that the performance of proposed algorithm does not fluctuate with the distribution of signal frequency and can achieve the very close performance to CZT and GD with three iterations. However, the computational complexity is reduced by over 75% in comparision with algorithms based on CZT and GD with three iterations.

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冯婕, 肖骏雄, 韩纪龙, 李蔚, 胡荣, 杨奇, 余少华. 基于幅度比值的低复杂度频偏估计算法[J]. 光学学报, 2015, 35(5): 0506007. Feng Jie, Xiao Junxiong, Han Jilong, Li Wei, Hu Rong, Yang Qi, Yu Shaohua. Low Complexity Frequency Offset Estimation Algorithm Based on Amplitude Ratio[J]. Acta Optica Sinica, 2015, 35(5): 0506007.

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