CO-OFDM系统中交叉相位调制效应的研究

发布时间：2019-02-25 11:10

【摘要】：XPM效应起源于光纤中的克尔非线性效应,即在WDM系统中,一个信道内传输光波的光强的变化会通过交叉相位调制对其他信道的光波进行相位调制,同时GVD将此相位调制转化为幅度调制。XPM效应引起的信号相位噪声以及幅度噪声,将会给相干光调制系统带来极大损伤,且该损伤会随着WDM系统中信道间隔的不断减小以及入纤功率的增加而逐渐加强。在过去的XPM研究,主要考虑的是XPM效应对单载波调制系统性能的影响,并对其产生的机理以及补偿方法进行了深入的探讨和研究。但是,XPM效应对多载波调制系统的影响,尤其是CO-OFDM系统的分析和深入研究屈指可数。CO-OFDM系统具有较高的PAPR且对正交性要求严格,势必对XPM引起的相位噪声非常敏感。因此XPM串扰是CO-OFDM系统中不可忽略的损伤,本论文将研究波分复用的OFDM系统中的XPM效应。首先,本论文介绍CO-OFDM系统中非线性损伤机理,包括SPM、XPM、FWM等。然后通过求解频域的非线性薛定谔方程,建立了基于Volterra级数的信道间XPM数学模型。采用Volterra级数对XPM进行分析,可以同时计算光纤中的色散和XPM损伤,不需要再分开建立GVD存在情况下信号幅度噪声与相位噪声之间的转化关系式。其次,我们将此XPM数学模型拓展到色散管理系统中,并在此基础上建立了可以用来预测XPM效应的基于Volterra级数的传输滤波器模型。然后,我们将此滤波器模型应用于OFDM/OOK混合系统中,并且预测出了OOK信道产生的XPM串扰对OFDM系统性能的影响。最后,考虑到XPM引起的相位噪声严重影响CO-OFDM系统性能,我们提出使用CO-OFDM+DSB调制方式,来降低XPM相位噪声对CO-OFDM系统性能的影响。随着DSB调制频率的增加,XPM引起的相位噪声逐渐减小甚至可以忽略不计。然后,我们使用了OFDM WDM系统对其进行仿真验证。
[Abstract]:The XPM effect originates from the Kerr nonlinear effect in the optical fiber, that is, in the WDM system, the change of the intensity of the light wave transmitted in one channel will modulate the light wave of the other channel by cross-phase modulation. At the same time, GVD transforms this phase modulation into amplitude modulation. The signal phase noise and amplitude noise caused by XPM effect will cause great damage to coherent optical modulation system. The damage increases with the decrease of channel spacing and the increase of fiber power in WDM system. In the past XPM research, the main consideration is the effect of XPM effect on the performance of single-carrier modulation system, and the mechanism of its generation and compensation methods have been deeply discussed and studied. However, the effect of XPM effect on multicarrier modulation systems, especially on the analysis and in-depth study of CO-OFDM systems, is very limited. CO-OFDM systems have high PAPR and strict requirements for orthogonality, which is bound to be very sensitive to the phase noise caused by XPM. Therefore, XPM crosstalk is a damage that can not be ignored in CO-OFDM system. This paper will study the XPM effect in WDM OFDM system. Firstly, this paper introduces the nonlinear damage mechanism of CO-OFDM system, including SPM,XPM,FWM and so on. Then, by solving the nonlinear Schrodinger equation in frequency domain, an inter-channel XPM mathematical model based on Volterra series is established. Using Volterra series to analyze XPM, the dispersion and XPM damage in optical fiber can be calculated simultaneously, and the transformation relationship between signal amplitude noise and phase noise in the presence of GVD does not need to be established separately. Secondly, we extend the XPM mathematical model to the dispersion management system, and establish a transmission filter model based on Volterra series which can be used to predict the XPM effect. Then, we apply the filter model to OFDM/OOK hybrid system, and predict the influence of XPM crosstalk generated by OOK channel on the performance of OFDM system. Finally, considering that the phase noise caused by XPM seriously affects the performance of CO-OFDM system, we propose to use CO-OFDM DSB modulation to reduce the influence of XPM phase noise on the performance of CO-OFDM system. With the increase of DSB modulation frequency, the phase noise caused by XPM is gradually reduced or even negligible. Then, we use the OFDM WDM system to simulate it.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN929.1

【相似文献】