【作者】 张雷；

【导师】 许渤；

【作者基本信息】 电子科技大学 ， 通信与信息系统， 2016， 硕士

【摘要】 当今,除了长距离光网络用于覆盖上千公里的骨干网传输外,短距离光网络也被广泛的应用在城域网中来实现大流量的集中接入访问。根据预测,未来几年短距离光网络中流量的增长将远远超过长距离光网络流量的增长。此外,因为短距离光网络的接入终端和用户的数量远远大于长距离光网络中的数量,所以其花费和能耗较长距离光网络大的多。如何在保证通信质量的同时降低短距离光网络的成本及功耗变成了短距离光网络是否能够实现大量商用的关键。利用信道均衡技术改善短距离光网络在成本和功耗的方面的表现无疑是一个很好的选择。本文首先对影响低成本高速光传输系统性能的因素进行了分析,发现符号间串扰(Inter-Symbol Interference,ISI)是影响系统性能的最主要因素,而造成系统内ISI的主要因素是光纤信道的色散和低成本器件的低通滤波效应。众所周知,可以在系统接收端利用均衡技术来消除系统中存在的不同符号间的串扰。本文除了对信道均衡的基本原理进行了阐述外,重点研究了发送速率为25GBauds,采用PAM4调制方式并且数模转化器有效带宽不足的低成本高速光传输系统采用常见的前馈均衡器,判决反馈均衡器,最大似然序列估计器时的性能表现。这些研究既包括了采用VPI软件加Matlab软件进行的仿真验证,也包括了利用实际器件进行的离线实验验证,为降低当前短距离高速光传输系统成本和功耗提供了一定的依据。除了对不同均衡器的算法进行了研究,本文为了达到降低Viterbi算法复杂度进而降低系统实现成本的目的还对M算法进行了研究。此外,根据奈奎斯特准则,在低成本的系统中采用的器件的带宽往往不能满足发送信号的带宽需求,所以本文还研究了发送信号带宽仅为其发送速率一半的Nyquist波形信号,大幅度降低了信号对系统带宽的需求。最后,受到Nyquist波形信号带宽要求低的启发,本文提出了一种有记忆PAM调制方法,它具有信号带宽小于信号发送速率并且信号波形实现简单的特点。通过仿真验证了有记忆PAM调制方法的正确性,并证明采用这种调制方式的系统的性能要好于采用无记忆PAM调制方式的系统的性能。通过对以上技术的研究,本文为降低采用MLSE的25GBauds的高速光传输系统的成本提供了一些有意的结论,为下一代高速光传输系统的大规模商用做出了一定贡献。更多还原

【Abstract】 Besides the long-haul optical networks covering over thousands of kilometers for backbone transmission, short reach optical networks(SR-ONs) are widely deployed in metro-area for aggregation and accessing. As predicted, the growing bandwidth demanding from SR-ONs will be much more than that from the long-haul optical networks in the near future. Besides, there are tremendous amounts of optical terminals and end-users in SR-ONs compared with the long-haul transmission systems and thus will induce large cost and huge energy consumption. So, the power and cost efficiency should be the key consideration for SR-ONs besides the transmission performance. Using the channel equalization technology to improve short-distance optical networks in terms of cost and power consumption performance is undoubtedly a good choice.Firstly, the factors affecting the performance of low-cost, high-speed optical communication systems were analyzed and found that inter-symbol interference(ISI) is the most important factor affecting system performance, but the main factor causing the ISI in system is fiber Channel and low-cost device lead to low-pass filtering effect. As we all know, the receiver in communication system can use the equalizer to eliminate ISI. In this paper, the basic principle of channel equalization are described, in addition, the focus on performance of the low-cost and high-speed optical communication system with transmission rate of 25 GBauds, using PAM4 modulation and digital-analog converter lack of effective bandwidth, common equalizers(including the use of feed forward equalizer(FFE), decision feedback equalizer(DFE) and maximum likelihood sequence estimator(MLSE)). These studies include both using VPI software plus Matlab software for the simulation and actual devices off-line experiments, which provide a certain basis of system cost and power consumption to reducing the current short-distance high-speed optical communication.In addition to the different equalizer algorithms were studied, this paper also studied the M algorithm in order to reduce the complexity of the Viterbi algorithm to achieve the purpose of reducing system cost. Further, according to the Nyquist criterion, this paper studied the Nyquist signal waveform which transmission rate is half of its signal bandwidth,largely reducing the signal’s demand to signal bandwidth on the system, eliminating the ISI caused by the filtering effect of insufficient bandwidth device. In addition, inspired by the lower bandwidth requirements of Nyquist signal waveform, this paper presents a kind of method which can memory PAM modulation, its signal bandwidth is less than the signal transmission rate and has simple signal wave. Simulation results have shown the correctness of method can memory PAM modulation and proven its performance is better than the memory-free PAM modulation system. Through the study of those technologies mentioned above, this paper concluded some idea to reduce the cost of using the MLSE of single-mode optical fiber communication system with 25 GBauds and make a certain contribution on commercial using of high-speed optical communication system for next generation.更多还原