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相干光WDM系统相位估计和XPM效应的研究

发布时间:2019-01-05 02:18  文章来源:笔耕文化传播
【摘要】:高速相干光通信和大容量波分复用系统(WDM)是当前光纤传输领域的主要技术。在相干光WDM系统中,以交叉相位调制(XPM)为代表的光纤非线性效应是影响系统性能的主要因素。本文针对相干光WDM系统中相位估计和XPM效应,在理论分析、系统建模、算法构建和性能仿真等方面对系统性能优化进行了全面深入的研究。论文针对单信道相干光通信系统,提出了一种弹性相位估计(PE)算法。通过最大似然方法求取权重系数,从而消除传统PE接收机块长度效应对系统的影响。通过理论分析,给出了弹性PE接收机的相位差方差公式进行系统性能的预测。其次,论文基于小信号的分析方法,XPM强度噪声通过近似处理可以转化为乘性噪声的形式,论文提出了一个整体的XPM效应模型以描述XPM强度噪声和XPM相位噪声对系统的影响。理论和仿真显示XPM强度噪声主要表现为信噪比(SNR)的损伤。论文针对QPSK/OOK混合WDM系统,基于XPM相位噪声的自相关函数,给出了QPSK信道带有M次幂和DA-ML PE接收机的相位差方差表达式,从而进行最优块长度的理论预测。在QPSK信道PE接收机中引入权重系数,从而消除QPSK/OOK混合WDM系统中的块长度效应。针对16-QAM相干光WDM系统中,基于XPM相位噪声的自相关函数和16-QAM信号功率的统计特性,给出了传统PE算法的相位差方差表达式,从而进行最优块长度的预测。为了消除16-QAM WDM系统PE接收机的块长度效应,权重系数被引入到PE接收机中,理论和仿真显示弹性PE接收机在16-QAM相干光WDM系统中不再受到块长度效应的影响。论文最后针对OFDM WDM系统,提出了一种相邻信道频谱搬移减小XPM效应的方法。XPM强度噪声方差随着中频频率(IF)的增加呈现变化的稳定性,XPM相位噪声方差随着IF的增加呈现单调下降特性。CO-OFDM信道在XPM效应和放大的自发辐射(ASE)噪声作用下,给出了误码率(BER)表达式,从而验证频谱搬移降低XPM效应方法的有效性。
[Abstract]:High speed coherent optical communication and large capacity wavelength division multiplexing system (WDM) are the main technologies in the field of optical fiber transmission. In coherent optical WDM systems, the nonlinear effect of cross-phase modulation (XPM) is the main factor affecting the performance of the system. In this paper, phase estimation and XPM effect in coherent optical WDM systems are studied in detail in terms of theoretical analysis, system modeling, algorithm construction and performance simulation. In this paper, an elastic phase estimation (PE) algorithm is proposed for single channel coherent optical communication systems. The weight coefficient is obtained by the maximum likelihood method to eliminate the influence of block length effect of traditional PE receiver on the system. Based on the theoretical analysis, the phase difference variance formula of elastic PE receiver is given to predict the system performance. Secondly, based on the small signal analysis method, XPM intensity noise can be transformed into multiplicative noise by approximate processing. A global XPM effect model is proposed to describe the influence of XPM intensity noise and XPM phase noise on the system. Theoretical and simulation results show that XPM intensity noise is mainly represented by SNR (SNR) damage. In this paper, based on the autocorrelation function of XPM phase noise, the expression of phase difference variance of QPSK channel with M power and DA-ML PE receiver is given for QPSK/OOK hybrid WDM system, and the optimal block length is predicted theoretically. The weight coefficient is introduced into the PE receiver of QPSK channel to eliminate the block length effect in the QPSK/OOK hybrid WDM system. Based on the autocorrelation function of XPM phase noise and the statistical characteristics of 16-QAM signal power in 16-QAM coherent optical WDM system, the expression of phase difference variance of the traditional PE algorithm is given to predict the optimal block length. In order to eliminate block length effect of PE receiver in 16-QAM WDM system, weight coefficient is introduced into PE receiver. Theoretical and simulation results show that elastic PE receiver is no longer affected by block length effect in 16-QAM coherent optical WDM system. Finally, for OFDM WDM system, a method of reducing XPM effect by spectrum shift of adjacent channel is proposed. The stability of XPM intensity noise variance changes with the increase of intermediate frequency (IF). The variance of XPM phase noise decreases monotonously with the increase of IF. Under the influence of XPM effect and amplified spontaneous emission (ASE) noise, the expression of BER (BER) is given. The effectiveness of spectrum shift method to reduce XPM effect is verified.
【学位授予单位】:南京邮电大学
【学位级别】:博士
【学位授予年份】:2016
【分类号】:TN929.1


本文编号:2401129


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