16-QAM高速相干光接收机的载波恢复算法研究

发布时间：2018-03-06 21:31

本文选题：相干光通信　切入点：16-QAM调制信号　出处：《北京交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着信息时代的来临,传统基于强度调制/直接检测的低速光通信系统已无法满足日益增长的带宽需求。而基于高阶调制、相干检测和数字信号处理技术的高速相干光通信网络具有高速率、高频谱利用率、低成本等优势,是下一代高速通信网的发展方向之一。结合相干检测和数字信号处理技术的数字相干光接收机,不仅可以充分保留载波幅度、相位及偏振等信息,还可以在电域中对光纤链路损伤及噪声进行很好的恢复和补偿,成为近年来光通信领域的研究热点。本文主要围绕基于16-QAM调制码型、相干检测及数字信号处理技术的高速相干光通信系统进行研究,重点研究了发射端激光器与本地振荡器间引入的频偏及相位噪声对系统性能的影响,实现了数字相干光接收机对载波频偏和载波相位的准确估计及恢复。主要完成以下工作:(1)研究方型16-QAM光信号的生成方式及原理,采用四电平驱动IQ调制器的光信号生成方式搭建112Gb/s 16-QAM相干光通信系统仿真平台,并利用载波频偏估计算法及载波相位估计算法对接收信号进行载波恢复。(2)研究基于部分星座点和基于训练序列的载波频偏估计算法。比较分析在112Gb/sl6-QAM调制格式相干光通信系统中,两种载波频偏估计算法的估计范围、估计精度和运算复杂度,讨论了系统残余频偏对载波相位估计的影响。(3)研究多种载波相位估计算法。本文对目前性能较好、可适用于16-QAM及其他高阶调制码型的载波相位估计算法进行研究,并从改进型ViterbiViterbi算法和盲相位搜索(BPS,Blind Phase Search)级联算法对其进行分类阐述,比较并分析八种载波相位估计算法在16-QAM相干光通信系统中的线宽容忍度及硬件复杂度。(4)提出了一种基于BPS的线性逼近(LA,Line Approximation)载波相位估计算法。阐述了 LA载波相位估计算法的基本原理和实现流程,通过仿真得到该算法的最佳测试相位点,同时分析了 LA载波相位估计算法的误码率、线宽容忍度、硬件复杂度及频偏容忍度。利用LA载波相位估计算法对112Gb/s 16-QAM相干光通信系统接收信号的相位进行恢复,仿真结果显示,LA算法的激光器线宽容忍度与BPS算法相近;其硬件复杂度比BPS算法的硬件复杂度降低了2.13/2.18/2.91/2.06(乘法器/加法器/比较器/判决器)倍;当残余频偏超过30MHz时,LA算法对接收信号的恢复能力优于BPS算法。
[Abstract]:With the advent of the information age, the traditional low-speed optical communication systems based on intensity modulation / direct detection can no longer meet the increasing bandwidth requirements. The high speed coherent optical communication network based on coherent detection and digital signal processing has the advantages of high rate, high spectral efficiency and low cost. Digital coherent optical receiver combined with coherent detection and digital signal processing technology can not only fully retain carrier amplitude, phase and polarization information. It can also be used to recover and compensate the damage and noise of optical link in the electric domain, which has become the research hotspot in the field of optical communication in recent years. This paper mainly focuses on the modulation code type based on 16-QAM. The high speed coherent optical communication system based on coherent detection and digital signal processing technology is studied. The influence of frequency offset and phase noise introduced between the transmitter laser and the local oscillator on the performance of the system is studied. The accurate estimation and recovery of carrier frequency offset and carrier phase are realized by digital coherent optical receiver. The following work is accomplished: 1) the generation method and principle of square 16-QAM optical signal are studied. The simulation platform of 112Gb / s 16-QAM coherent optical communication system is built by using the optical signal generation method of four-level drive IQ modulator. The carrier frequency offset estimation algorithm based on partial constellation and training sequence is studied by using carrier frequency offset estimation algorithm and carrier phase estimation algorithm for received signal. A comparative analysis is made in 112Gb / sl6-QAM modulation format coherent optical communication system. The estimation range, estimation accuracy and computational complexity of two carrier frequency offset estimation algorithms are discussed. The influence of residual frequency offset on carrier phase estimation is discussed. The carrier phase estimation algorithm suitable for 16-QAM and other high-order modulation code types is studied, and the improved ViterbiViterbi algorithm and the blind phase search BPS-Blind Phase search algorithm are classified and described. Comparing and analyzing the linewidth tolerance and hardware complexity of eight carrier phase estimation algorithms in 16-QAM coherent optical communication systems, a linear approximation line approximation algorithm based on BPS is proposed. The LA carrier phase estimation algorithm is described. The basic principle and implementation flow of bit estimation algorithm, The optimal test phase point of the algorithm is obtained by simulation. Meanwhile, the error rate and line width tolerance of the LA carrier phase estimation algorithm are analyzed. Hardware complexity and frequency offset tolerance. The phase recovery of 112Gb / s 16-QAM coherent optical communication system is performed by using LA carrier phase estimation algorithm. The simulation results show that the linewidth tolerance of the LA algorithm is similar to that of BPS algorithm. The hardware complexity of the algorithm is 2.13 / 2.18 / 2.91 / 2.06 (multiplier / adder / comparator / decider), and when the residual frequency offset exceeds 30MHz, the recovery ability of the LA algorithm is better than that of the BPS algorithm.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.1

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