相干光通信系统中信道均衡与频偏估计算法研究

发布时间：2018-04-16 15:04

本文选题：相干光通信 + 信道均衡　；参考：《北京科技大学》2016年博士论文

【摘要】：相干光通信系统集成了光偏振复用技术、多级调制技术、相干光检测技术和数字信号处理技术,具有频谱效率高的优点,拥有比传统光通信系统更高的信道容量。因此,相干光通信现已成为下一代高速光通信主干网的关键技术。本文比较详细地介绍了相干光通信系统的组成,着重对数字相干光接收机的信道均衡与频偏估计算法进行了深入的研究。论文的主要创新点包括：(1)提出一种在数字相干光接收机中使用维纳滤波器进行色散补偿的时域均衡方法。维纳滤波器能够补偿色散、滤除噪声,进而得到对发送信号的最小均方误差意义下的最优估计信号。应用于多速率系统中的维纳滤波器的抽头系数可根据信道的冲击响应和信噪比计算得到。16-QAM相干光通信系统的数值仿真结果表明,使用维纳滤波器进行色散均衡的误码率性能优于现有的时域均衡方法。(2)针对QPSK相干光系统,通过对基于符号相位频谱的频偏估计算法的深入研究发现,其频偏估计范围仅为-Rs/12至Rs/8,其中Rs为符号速率。针对其存在问题,修改了频偏符号的判决方法,并进行了数值仿真验证。所得改进算法的频偏估计精度不变,仅增加了很少的计算量使其估计范围扩大到了-Rs/8至Rs/8。(3)针对16-QAM相干光系统,提出了一种基于相邻各类符号相位差的频偏估计算法。与现有的仅将连续的一类符号(CCIS)用于频偏估计的频偏估计算法不同的是,所提出的新算法将所有的16-QAM符号(包含一类和二类符号)都用于频偏估计。考虑到不同类符号的兼容性,使用8次幂运算来移除调制的数据相位。需说明的是,二类符号在8次幂运算之前应将其相位旋转π/8。得益于用来进行频偏估计的数据量的增加,所提出的频偏估计算法具有比传统的CCIS算法更高的估计精度,在误码率达到10-3时所需的符号信噪比有0.7dB的改善。
[Abstract]:Coherent optical communication system integrates optical polarization multiplexing, multilevel modulation, coherent optical detection and digital signal processing. It has the advantages of high spectral efficiency and higher channel capacity than traditional optical communication systems.Therefore, coherent optical communication has become the key technology of the next generation high-speed optical communication backbone network.In this paper, the composition of coherent optical communication system is introduced in detail, and the channel equalization and frequency offset estimation algorithms of digital coherent optical receiver are studied in detail.The main innovation of this paper is to propose a time-domain equalization method using Wiener filter to compensate dispersion in digital coherent optical receiver.Wiener filter can compensate dispersion, filter noise, and then obtain the optimal estimation signal in the sense of minimum mean square error of the transmitted signal.The tap coefficient of Wiener filter applied in multi-rate system can be calculated according to the impulse response and signal-to-noise ratio of the channel to obtain the numerical simulation results of .16-QAM coherent optical communication system.The BER performance of Wiener filter for dispersion equalization is better than that of the existing time-domain equalization method. (2) for QPSK coherent optical systems, the frequency offset estimation algorithm based on symbol phase spectrum is deeply studied.The estimation range of frequency offset is only between Rsr / 12 and Rsr / 8, where Rs are symbolic rates.In order to solve the problem, the decision method of frequency offset symbol is modified, and the numerical simulation is carried out.The frequency offset estimation accuracy of the improved algorithm is invariable, and the estimation range is extended to Rsr / 8 to RsR / 8.3 with only a small amount of computation.) for 16-QAM coherent optical systems, a frequency offset estimation algorithm based on the phase difference of adjacent symbols is proposed.Different from the existing frequency offset estimation algorithm which uses only a continuous class of symbols for frequency offset estimation, the proposed new algorithm uses all 16-QAM symbols (including one and two kinds of symbols) for frequency offset estimation.Considering the compatibility of different classes of symbols, eight power operations are used to remove the data phase of the modulation.It is important to note that the second class of symbols should rotate their phase 蟺 / 8 before 8 power operations.Due to the increase of the amount of data used for frequency offset estimation, the proposed frequency offset estimation algorithm has higher estimation accuracy than the traditional CCIS algorithm, and the signal to noise ratio (SNR) of the symbol needed when the BER reaches 10-3 is improved by 0.7dB.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN929.1

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