【作者】 张旭；

【导师】 余少华；

【作者基本信息】 华中科技大学 ， 电子科学与技术， 2021， 博士

【摘要】 随着近10年来相干光通信技术的不断发展,高速相干光通信设备已经在骨干网中得到了大规模商用。从2011年,单波长100 Gbit/s技术开始商用,目前已成为骨干网最普遍的线路速率,到2018年,单波长200 Gbit/s和400 Gbit/s技术逐步开始商用,将来实现800 Gbit/s或1 Tbit/s技术的商用化已经成为必然趋势。随着网络业务的快速发展和通信需求的不断更新,相干光通信技术凭借在高速干线传输网上的成功逐渐向其他场景渗透,然而由于不同应用场景的自身特点,传统的相干光通信技术还存在一些问题有待解决。在短距离场景中,如接入网、数据中心等,高速数据业务的增长为相干光通信技术提供了广阔的发展空间。然而由于短距离场景对低成本和低功耗的要求,使得传统高成本高功耗的相干光通信技术难以被接受。另外在超长跨距光通信领域,由于具有更高的接收灵敏度和信噪比容限,相干光通信技术成为了最佳解决方案。然而由于光纤处于自然环境中容易受到外界因素的干扰,使得传统相干光通信技术的应用还面临诸多实际问题。与此同时,在目前相干光通信技术已经大规模商用的骨干网中,基于波分复用技术的网络带宽和节点容量不断增长。随着互联网流量的持续增长,大带宽业务调度需求迅速增加,如何在光层实现波长信道管理,成为了骨干网场景面临的新问题。针对以上问题,本文对高速相干光传输系统在相关领域的数字信号处理算法方面开展了一系列研究,主要成果和创新点如下:(1)主要针对接入网、数据中心等短距离应用场景中,进一步降低相干技术复杂度的需求,研究了简化的数字信号处理算法,提出了一种新型自适应信道均衡算法结构,然后针对所提出的新型算法结构,提出了一种新型误差计算方法提升算法性能。新型算法结构在整体上可减少约40%左右的乘法器资源。基于实时相干传输平台,将该算法在接收端实现,并进行了传输实验。在背对背和60 km传输实验中,相比传统算法的性能损失仅为0.2～0.3 d B。新算法在减少资源消耗的同时,对模数转换的精度需求不变,而且具有比传统算法更强的偏振解复用能力。(2)主要针对超长跨距应用场景中,存在外界干扰造成光信号偏振态快速旋转的问题,提出了一种基于偏振态监测与反馈的自适应滤波器算法结构。首先通过提取自适应滤波器系数计算斯托克斯向量,实现了对偏振态变化情况的实时监测,然后根据偏振态变化情况调整滤波器更新系数大小,提升了算法的偏振跟踪能力。经实验验证,所提出的算法结构可将原有算法的偏振跟踪能力提升4倍以上。在算法资源消耗方面,增加的部分仅为原有算法的1%。(3)主要针对骨干网场景中,在光层实现波长信道管理的需求,提出了一种新型基于导频的光标记信号收发系统。通过子载波索引调制,对不同波长加载不同频段的光标记信号,在接收端仅通过1个光电二极管就能完成对所有光标记信号的接收。同时在数字信号处理方面,在发送端通过相位调整算法降低信号峰均功率比,在接收端通过相偏估计补偿算法,以及频谱累加求和算法提高光标记信号的信噪比,提高了光标记信号的传输性能。通过实验优化了相关参数,并验证了该方案在100 Gbit/s相干波分复用光网络中的可行性。更多还原

【Abstract】 With the development of coherent optical communication technology in recent 10 years,high-speed coherent technology has been widely used in backbone transmission network.From 2011,the single wave length technology of 100 Gbit/s has been commercial,and has become the most common line speed of transmission network.By 2018,200 Gbit/s and 400 Gbit/s technology has been gradually commercial,and the commercialization of800 Gbit/s or 1 Tbit/s technology has become an inevitable trend in the future.With the continuous development of network services and communication demands,coherent optical communication technology began to develop into other fields.However,due to the characteristics of different application network,traditional coherent optical communication technology still has some problems to be solved.In short-range network,such as access network,data center and so on,the demand of high-speed data services provides the development opportunity for coherent optical communication technology.However,due to the requirement of low cost and low power consumption in short distance network,the traditional coherent optical communication technology with high cost and high power is difficult to be accepted.In addition,in the field of ultra long span optical communication,coherent optical communication technology has become the best solution based on its higher receiving sensitivity and signal to noise ratio tolerance.However,due to the fiber in the natural environment,it is easy to be affected by some environment factors.The application of traditional coherent optical communication technology still faces many practical problems.At the same time,in the backbone network where coherent optical communication technology has been widely used,based on wavelength division multiplexing technology,the network bandwidth and node capacity are growing rapidly.With the continuous growth of Internet traffic,the demand for large bandwidth service scheduling is increasing rapidly.How to achieve wavelength channel management in the optical layer has become a new problem in the backbone network.In view of the above problems,this dissertation has carried out a series of research on signal processing algorithms related to digital coherent optical transmission system.The main achievements and innovations of this thesis are as follows:(1)Mainly for short-range applications such as access network and data center,to further reduce the complexity of coherent technology,a simplified digital signal processing algorithm is studied,and a new adaptive channel equalization algorithm structure is proposed.Then,according to the new algorithm structure,a new error calculation method is proposed to improve the performance of the algorithm.The new algorithm structure can reduce about 40% multiplier resource.Based on the real-time coherent transmission platform,the algorithm is implemented at the receiving side.The transmission experiment is carried out to verify the performance.In the back-to-back and 60 km transmission experiments,compared with the traditional algorithm,the performance penalty of the proposed algorithm is only about 0.2～0.3 d B.The proposed algorithm not only reduces the resource consumption,but also has the same requirement for the sampling wideth of analog to digital converter.And it has stronger polarization demultiplexing ability than the traditional algorithm.(2)Mainly for ultra long span transmission network,a novel adaptive filter algorithm structure with state of polarization monitoring and feedback is proposed to solve the problem of polarization state fast rotation caused by external environment interference.Firstly,by extracting the filter tap coefficients in adaptive filter,the Stokes vector is calculated to obtain the state of polarization rotation,which realizes the real-time monitoring of polarization state rotation.Then,the update coefficient of the filter is adjusted according to the change of polarization state,and the polarization tracking ability of the algorithm can be improved.The transmission experiment is carried out to verify the performance.The results show that the proposed algorithm structure can improve the polarization tracking ability of the traditional algorithm structure by more than 4 times.Compared with resources consumption of the traditional algorithm structure,the increased resource of the proposed algorithm is only 1%.(3)Mainly aiming at the requirement of wavelength channel management in optical layer in backbone network,a new optical label signal transceiver system based on pilot is proposed.Based on the optial subcarrier index modulation,the optical labelling signals of different wavelengths are loaded in different frequency bands.Therefore,the whole band optical labelling signals can be recognized by only one photo diode at the receiver.In terms of digital signal processing,the phase adjustment algorithm is used to reduce the signal peak to average power ratio at the transmitter side.At the receiver side,phase offset estimation and compensation algorithm,and the overlap summation algorithm in frequency domain,are implement to improve the signal to niose ratio.The relevant parameters are optimized through experiments,and the feasibility of the optical label scheme in 100 Gbit/s coherent wavelength division multiplexing optical network is verified.更多还原