基于FCM-KNN的相干光环形QAM系统符号判决优化  

Performance improvement of coherent optical circular 16-QAM system by optimizin g symbol decision boundary based on FCM-KNN algorithm

作　　者：卢瑾[1] 任宏亮[1] 郭淑琴[1] 覃亚丽[1] 胡卫生[2] LU Jin;REN Hong-liang;GUO Shu-qin;QIN Ya-li;HU Wei-sheng(College of Information and Engineering,Zhejing University of Technology,Hangzhou,Zhejiang 310023,China;State Key Laboratory of Advanced Optical Communication Systems and Networks,Shanghai Jiao Tong University,Shanghai,200240,China)

机构地区：[1]浙江工业大学信息工程学院,浙江杭州310023 [2]上海交通大学区域光纤通信网与新型光通信系统国家重点实验室,上海200240

出　　处：《光电子．激光》2020年第6期575-586,共12页Journal of Optoelectronics·Laser

基　　金：国家自然科学基金(61675184,61675183,61405178);浙江省自然科学基金(LY20F050009);上海交通大学区域光纤通信网与新型光通信系统国家重点实验室开放基金(2020GZKF013)资助项目.

摘　　要：针对高阶环形正交幅度调制(QAM)的相干光通信系统,提出了一种模糊C均值算法和K最近邻算法相结合的非线性均衡算法。对接收端经相位噪声补偿后的数据,先用FCM算法有效剪裁训练数据,同时对测试数据进行分类判决,从而极大降低了后续KNN算法的计算复杂度。即首先计算训练集的初始质心和各数据点的初始隶属度,经过迭代计算收敛后,得到最终的质心和各数据点的隶属度。然后将质心隶属度大于某阈值的测试数据点作为训练数据,计算各测试数据与各训练集质心的距离对其暂时分类,接下来进行KNN算法分类。同时对测试集进行分类判决,即对距该质心距离低于阈值的测试数据根据欧式距离直接判决,大于阈值的测试数据用以上KNN方法进行判决。该算法基于112 Gbit/s单载波单偏振相干检测环形16QAM单载波系统传输距离为1040 km进行了非线性均衡效果仿真验证。仿真结果表明,本文所提出的FCM-KNN算法可取得和KNN算法几乎相同的非线性均衡效果,而其复杂度比后者可降低近20倍,对高阶QAM相干光通信系统长距离传输具有重要意义。A nonlinear equalization algorithm has been proposed through combining fuzzy c-means(FCM)algorithm and K-nearest neighbor(KNN)in coherent optical s ystem with high-order quadrature amplitude modulation(QAM).After performing p h ase recovery at the receiver,a certain number of the training data are tailored by FCM algorithm,and the test data are classified to make decision,which redu ce the computational complexity greatly in subsequent KNN algorithm.The initial centroid and membership grade are firstly calculated for the original training data.After several iterations,the ultimate centroid and membership grade are o btained.The data point is adopted as the tailored training data when its member ship grade is larger than the threshold,and the test point is temporarily class ified according to the distance between it and the centroids.Subsequently,the KNN algorithm is performed to obtain the final classification results.For a 28G baud single carrier single polarization circular 16quadrature amplitude modulat ion(16-QAM)coherent transmission system with 1040km trans mission distance,the numerical simulations have been performed in order to investigate the nonlinear equalization performance of the proposed FCM-KNN algorithm.It is proved by th e simulation results that the FCM-KNN scheme shares the same performance with th e KNN algorithm,and moreover its computational complexity is twenty times less t han that of KNN algorithm,which benefits greatly to the application of coherent optical QAM transmission technology in long distance optical fiber transmission.

关 键 词：相干光QAM系统 高阶正交幅度调制 模糊C均值算法(FCM) K最近邻算法(KNN) 非线性均衡 

分 类 号：TN913.7[电子电信—通信与信息系统]