Accurate Two-Stage Frequency Offset Estimation for Coherent Optical Systems
Accurate Two-Stage Frequency Offset Estimation for Coherent Optical Systems
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DOI：
10.1109/lpt.2012.2232288
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发表时间：
2013
影响因子：
2.6
通讯作者：
D. Huang;T. Cheng;Changyuan Yu
中科院分区：
文献类型：
--
作者：
D. Huang;T. Cheng;Changyuan Yu
本文提出了一种基于相位差法的两级前馈频偏估计算法。该算法的第一级通过对相邻两个符号之间的相位差进行平均来产生一个粗略的FOE，并对信号进行补偿。FOE的第二级通过对具有距离L的两个符号的相位差进行平均来估计残余FO，这提供了明显更大的噪声容限，从而提高了系统性能。所提出的FOE可以应用于正交相移键控和16正交幅度调制系统。仿真结果表明，在激光线宽较小的情况下，与传统的基于相位差的光纤陀螺相比，该光纤陀螺的均方误差可以降低2个数量级。实验结果表明，提出的FOE给出了0.6-dB的光信噪比改善比经典FOE，这验证了它的实用性。
We present a two-stage feedforward frequency offset estimation (FOE) algorithm on the basis of the phase-difference method. The first stage of the proposed FOE generates a rough FOE through averaging the phase difference between two adjacent symbols and compensates the signals. The second stage of the FOE estimates the residual FO through averaging the phase difference of two symbols with distance L , which provides a significantly larger noise-tolerance and thus improves system performance. The proposed FOE can be applied to both quadrature phase-shift keying and 16-quadrature amplitude modulation systems. Simulations show that the mean square error of the proposed FOE can be reduced through an order of two in magnitude under small laser linewidth situation compared with the classic phase-difference-based FOE. The experimental result shows that the proposed FOE gives 0.6-dB optical-signal-to-noise-ratio improvement against the classic FOE, which validates its usefulness.