功率抖动信道中的实时时钟恢复算法  

Real-Time Clock Recovery Algorithm for Power Jitter Channel

作　　者：李永富 李岩 洪小斌[1,2] 郭宏翔 邱吉芳[1,2] 李蔚 左勇[1,2] 伍剑 Li Yongfu;Li Yan;Hong Xiaobin;Guo Hongxiang;Qiu Jifang;Li Wei;Zuo Yong;Wu Jian(School of Electronic Engineering,Beijing University of Posts and Telecommunications,Beijing 100876,China;State Key Laboratory of Information Photonics and Optical Communications,Beijing University of Posts and Telecommunications,Beijing 100876,China)

机构地区：[1]北京邮电大学电子工程学院,北京100876 [2]北京邮电大学信息光子学与光通信国家重点实验室,北京100876

出　　处：《光学学报》2021年第18期50-57,共8页Acta Optica Sinica

基　　金：国家重点研发计划(2019YFB1803601);国家自然科学基金(61875019,61675034);中央高校基本科研业务基金。

摘　　要：分析时钟恢复算法中环路滤波器比例增益系数对系统误码率的影响时发现,信号的误码率随比例增益系数的增大呈先减小后增大的变化趋势,且不同接收光功率下的最优比例增益系数不同。针对该问题,提出并实现了一种基于Gardner算法的全实时化动态比例增益系数全数字时钟恢复算法,以应对功率抖动信道并提高算法的灵敏度。此外,在基于Altera Stratix-V 5SGXMA7K2F40C3 FPGA平台的2.5 GBaud正交相移键控调制相干通信系统中对该算法进行了在线实验验证。以KP4中的前向纠错码门限2×10^(-4)为上限,当功率抖动频率较慢时,动态参数法能将系统到达该误码门限的最低接收光功率由固定参数法的-47 dBm降低至-49.5 dBm;当功率抖动频率较快时,固定参数法能承受最低功率为-46.5 dBm、抖动频率为100 Hz的抖动,而动态参数法能承受最低功率为-50 dBm、抖动频率为1 kHz的抖动。When analyzing the influence of proportional gain coefficient of the loop filter in the clock recovery algorithm on system bit error rate,we find that the bit error rate of the signal first decreases and then increases with the increase in proportional gain coefficient,and the optimal proportional gain coefficient varies with received power.In response to this problem,we propose a full-digital clock recovery algorithm having a full real-time dynamic proportional gain coefficient based on Gardner algorithm to deal with power jitter channels and improve the sensitivity of the algorithm.The algorithm is then verified by online experiments in a 2.5 GBaud coherent communication system built upon the Altera Stratix-V 5 SGXMA7 K2 F40 C3 FPGA platform and quadrature phase-shift keying modulation.With the forward error correction threshold of 2×10^(-4) in KP4 as upper limit,the dynamic parameter algorithm can reduce the minimum received power for the system to reach this threshold from-47 dBm of the fixed parameter algorithm to-49.5 dBm when the power jitter frequency is low.When the frequency is high,the lowest power and frequency of the jitter that the fixed parameter algorithm can withstand are-46.5 dBm and 100 Hz respectively,whereas those of the dynamic parameter algorithm are-50 dBm and 1 kHz respectively.

关 键 词：光通信 相干通信 相位调制 功率抖动信道 实时系统 时钟恢复算法 

分 类 号：TN929.1[电子电信—通信与信息系统]