相干光接收机的频偏估计和相位恢复研究

发布时间：2018-05-26 03:28

本文选题：循环前缀 + 相干光正交频分复用　；参考：《电子科技大学》2014年硕士论文

【摘要】：随着通信网络流量的快速增长,光通信网络正面临着高速、大容量、高效率的需求。近年来在诸多新型光调制传输技术中,光正交频分复用(OFDM)技术具有频谱利用率高,调制格式灵活,数字信号处理简单等优点,逐步被光通信领域研究人员重视和认同。相干光正交频分复用系统(CO-OFDM)可以实现射频到光域的线性互变,具有容量大、传输距离长、灵敏度高等特点,但CO-OFDM相比于其它系统更易受到频率偏移和激光器线宽引起的相位噪声的影响。针对CO-OFDM对频率偏移、相位噪声的敏感性,本文做了如下工作:(1)首先对OFDM技术的基本原理进行了阐述,包括OFDM数学模型,通过IDFT/DFT运算实现调制解调,循环前缀在OFDM系统中的重要性等,此外介绍了OFDM从发送端到接收端需要进行的关键信号处理模块,在理论分析基础上分析了相干光OFDM系统的优缺点。(2)搭建了基于VPI和Matlab联合仿真平台的100 G相干光OFDM仿真平台。理论分析,仿真验证了平台的正确性。(3)对激光器线宽相位噪声,光纤色散(CD)对系统的影响进行了理论推导,使用插入导频的算法对激光器线宽引起的相位噪声进行了估计和补偿,仿真验证该算法能有效的补偿激光器线宽给系统带来的影响。(3)从训练序列、循环前缀两个方面对频率同步算法进行了仿真分析,讨论了自相关强的FH共轭对称算法,通过仿真验证了FH算法能有效的进行定时同步和频率同步。与SC算法相比此算法使用了较短的训练序列完成准确的定时同步,且频率估计范围更大。对基于循环前缀的最大似然(ML)算法、集相关算法、基于S长度块相关连续符号算法三种算法进行了理论分析和仿真验证,得出三种算法可以完成小数倍频偏估计,需要和FH算法联合估计完成系统频率同步。基于S长度块算法具有算法简单,计算复杂度低,对循环前缀完整度要求低的特点。
[Abstract]:With the rapid growth of communication network traffic, optical communication network is facing the demand of high speed, large capacity and high efficiency. In recent years, optical orthogonal frequency division multiplexing (OFDM) technology has many advantages, such as high spectral efficiency, flexible modulation format, simple digital signal processing and so on. Coherent Optical orthogonal Frequency Division Multiplexing system (CO-OFDM) can realize linear alternation from RF to optical domain. It has the advantages of large capacity, long transmission distance and high sensitivity. But CO-OFDM is more susceptible to phase noise caused by frequency offset and laser linewidth than other systems. Aiming at the sensitivity of CO-OFDM to frequency offset and phase noise, this paper does the following work: 1) first, the basic principle of OFDM technology is expounded, including the mathematical model of OFDM, which is modulated and demodulated by IDFT/DFT operation. The importance of cyclic prefix in OFDM system is introduced. In addition, the key signal processing module of OFDM from the transmitter to receiver is introduced. On the basis of theoretical analysis, the advantages and disadvantages of coherent optical OFDM system are analyzed. (2) A 100G coherent optical OFDM simulation platform based on VPI and Matlab is built. Theoretical analysis and simulation verify the correctness of the platform. The influence of laser linewidth phase noise and fiber dispersion CDI) on the system is theoretically deduced. The phase noise caused by the linewidth of the laser is estimated and compensated by the insertion pilot algorithm. The simulation results show that the algorithm can effectively compensate the influence of the linewidth of the laser on the system. The frequency synchronization algorithm is simulated and analyzed in two aspects of cyclic prefix, and the FH conjugate symmetric algorithm with strong autocorrelation is discussed. The simulation results show that the FH algorithm is effective in timing synchronization and frequency synchronization. Compared with SC algorithm, this algorithm uses a short training sequence to complete accurate timing synchronization, and the frequency estimation range is larger. The maximum likelihood ML-based algorithm based on cyclic prefix, set correlation algorithm and S-length block correlation continuous symbol algorithm are theoretically analyzed and simulated. The system frequency synchronization needs to be completed by joint estimation with FH algorithm. The algorithm based on S-length block has the advantages of simple algorithm, low computational complexity and low requirement of cyclic prefix integrity.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.1;TN851

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