50-Gb/sPAM-4调制NG-PON系统中的基于特征向量构建的改进型SVM均衡算法

本文针对低成本下一代无源光网络(NG-PON)传 输系统中带宽限制和光纤累计色散所产生的严重码间串扰问题,提出了一种基于特征向量 构建的改进型支持向量机(SVM)的均衡 算法。该算法充分考虑了码间串扰信号的特性,并在此基础上构建了新颖的特征向量,从而 适用于带限NG-PON系统中。此外,为了实现对PAM-4信号的多分类任务,该算法采用了 多对多(MVM)的方法训练三个独立SVM分类器。本文搭建了基于10-G 带宽光电器件的 50-Gb/sPAM-4信号传输实验来进一步验证本算法的可行性。实验结 果表明,相比于经典 前馈均衡器(FFE)和判决反馈均衡器(DFE),本算法可将接收灵敏度在HD-FEC门限下 (BER=3.8e－3)提高约1dB,从而使系统 在不使用任何放大器的情况下功率预算达到了20 dB。 此外,本方案对CDR定时偏移误差更稳定,可在相当大的偏移范围内保持可观的性能。因 此,该方案可被应用在NG-PON系统中用于更好的提升系统传输性性能。

SVM-based equalization algorithm modified by feature vector construction enabled 50-Gb/s PAM-4modulation NG-PON system

In the high-speed next generation passive optical network (NG-PON) transmissio n system based on low bandwidth optical devices,severe inter-symbol interference (ISI) p roblem would be caused due to the limited bandwidth.In this paper,we proposes a support vector machine (SVM) equalization algorithm modified by feature vector c onstruction to improve the performance of high-speed bandwidth limited NG-PON system.Considering the characteristics of these systems,a novel feature vector i s constructed to achieve a new SVM-based equalizer suitable for band-limited NG -PON systems.In addition,a many-to-many (MVM) approach to train three independent SVM classifi ers is employed to achieve multi-classification tasks for PAM-4signals.A 50Gb/s PAM-4signal t ransmission experiment based on 10-G bandwidth transceiver is demonstrated to prove the feasibility of our new SVM-based equalizer.Experimental results show that,compared with the traditional feed-for ward equalizer (FFE) and decision feedback equalizer (DFE),the receiver sensitivity achieved by our s cheme can be improved by about 1dB under the HD-FEC threshold (BER=3.8E-3), which allows the system to achieve a power budget of 20dB without the use of any amplifier.Inaddition,our scheme is more s table for CDR timing offset errors,which maintains reliable equalization performance over a relativel y large margin of timing offset.Therefore,we believe the proposed modified SVM-based equalizer could be considered prospective candidate for NG-PON systems.