【作者】 吕红；

【导师】 付松年；

【作者基本信息】 广东工业大学 ， 信息与通信工程， 2023， 硕士

【摘要】 数字相干光纤通信因其高频谱效率和大传输容量已经成为光纤通信领域的优选技术方案。高速光信号经过光纤传输后会产生各种线性和非线性传输损伤,虽然数字均衡技术可以有效地补偿线性传输损伤,但光纤非线性已经成为光纤通信系统扩容的关键限制因素。数字副载波复用(digital subcarrier multiplexing,DSM)技术将高波特率的单载波传输划分为几个低波特率的并行副载波传输,副载波间无频谱重叠,可以显著提升对光纤非线性的容忍度,因此DSM技术近年来得到国内外学术界和产业界的关注。当前适用于单载波的数字信号处理(digital signal processing,DSP)技术无法直接应用于DSM信号,研究适用于DSM信号的数字均衡技术需求迫切。本论文从损伤机理分析和仿真实验验证对基于DSM的光纤通信系统数字均衡技术开展研究,主要创新性研究成果包括:(1)针对高频谱效率DSM光纤通信系统的盲频偏估计难题,首先提出一种低复杂度的盲频偏估计方案,在接收端的DSM频谱中识别副载波间的频谱下沉点实现频偏估计,并利用数字平滑滤波器提高频偏估计性能。基于4个副载波的35 Gbaud双偏振16阶正交幅度调制(dual-polarization 16-ary quadrature amplitude modulation,DP-16QAM)DSM信号开展实验验证,经过2560 km标准单模光纤传输后,实测频偏估计误差低于100 MHz,且对光滤波效应以及光纤非线性影响具有较高容忍度。进一步提出一种适用于高频谱效率DSM信号的盲频偏估计方案,通过计算固定频带内频谱分量总功率最大值所对应的频偏以完成频偏估计,采用包含4个副载波和8个副载波的25 Gbaud单偏振16QAM(single polarization 16-ary quadrature amplitude modulation,SP-16QAM)DSM信号开展实验验证,经过25 km标准单模光纤传输后,实验证明频偏估计误差低于35 MHz,对发射端整形滤波器的小滚降因子不敏感,满足高频谱效率DSM光纤通信系统应用需求。(2)针对DSM光纤通信系统的均衡增强相位噪声(equalization enhanced phase noise,EEPN),提出一种高频谱效率EEPN数字均衡算法,在色散补偿前分别重构出收发端半导体激光器的相位噪声,并在色散补偿前后分别补偿收发端相位噪声,从而实现EEPN的数字均衡。利用包含8个副载波的95.6 Gbaud双偏振64阶正交幅度调制(dual-polarization 64-ary quadrature amplitude modulation,DP-64QAM)DSM信号开展仿真验证,经过1000 km标准单模光纤传输后,相比于传统基于导频信号的均衡方案,所提均衡方案可获得0.2 d B的性能收益,同时具有更高的线宽容忍度,并节省两个副载波的导频占用,提升了传输系统频谱效率。更多还原

【Abstract】 Digital coherent fiber optical communication has become the optimal choice of fiber optical communication,because of its high spectral efficiency and large transmission capacity.Various linear and nonlinear transmission impairments occur,when high-speed optical signals are transmitted over standard single-mode fiber(SSMF).Although digital equalization technique can effectively compensation linear transmission impairments,the fiber nonlinearity becomes a key limiting factor for the capacity enhancement of fiber optical communication.Digital subcarrier multiplexing(DSM)can divide high baud-rate single-carrier transmission into several low baud-rate parallel subcarriers,without the spectral overlapping,which can significantly improve the tolerance of fiber nonlinearity.Therefore,DSM technique has attracted the worldwide research attentions from academic and industry in recent years.Meanwhile,since the current digital signal processing(DSP)technology applicable to single-carrier cannot be directly applied to the DSM signal,it is urgent to investigate the digital equalization technique applied for the DSM signal.My thesis is focused on the digital equalization technique of fiber optical communication system based on the DSM from both the impairments mechanism and the experimental verification.The main innovative research outcomes are summarized as follows:(1)In order to solve the problem of blind frequency offset estimation(FOE)for the DSM signals with high spectral efficiency(SE),we put forward a low complexity blind FOE algorithm,by identifying the spectral dip points among subcarriers in the DSM frequency spectrum at the receiver side,and then the FOE performance is improved by the use of a digital smoothing filter.A 35 Gbaud dual-polarization 16-ary quadrature amplitude modulation(DP-16QAM)DSM signal including 4 subcarriers is used for the experimental verification.After the transmission over 2560 km SSMF,the FOE error of the proposed scheme is less than 100 MHz,with the high tolerance of optical filtering effect and fiber nonlinearity.Meanwhile,a blind FOE algorithm,by calculating the frequency offset corresponding to the maximum power of the total spectral component within a fixed frequency band.A 25 Gbaud single-polarization 16-ary quadrature amplitude modulation(SP-16QAM)DSM signal including 8 subcarriers and 4 subcarriers is used for experimental verification.After the transmission over 25 km SSMF,the FOE error is less than 35 MHz,with the merit of small roll-off factor application,which satisfies the requirement of high SE DSM transmission.(2)In order to mitigate the equalization enhanced phase noise(EEPN)of DSM fiber optical transmission,a high SE EEPN equalization algorithm is proposed to reconstruct phase noise of semiconductor laser at receiver and transmitter,respectively,before the digital chromatic dispersion(CD)compensation.Before and after the digital CD compensation,the phase noise of each semiconductor lasers is compensated,respectively.The 95.6 Gbuad DSM signals,which contains 8 subcarriers dual-polarization 64-ary quadrature amplitude modulation(DP-64QAM),are used for numerical verification.After the transmission over1000 km SSMF,the proposed scheme can achieve 0.2 d B performance gain,in comparison with the traditional pilot based EEPN equalization scheme.Furthermore,our proposed scheme has a higher tolerance of linewidth and high SE,without scarifying the pilot occupation of two subcarriers.更多还原