Studies On Key Technologies Of Signal Processing Based On Nonlinear Effects In Optical Access And Interconnection Networks

With the birth and development of a series of high-rate,high-quality,and high-bandwidth services such as megadata,cloud computing,the Internet of Things,data centers,and virtual reality(VR),the network bandwidth has increased rapidly,which puts forward higher requirements on the carrying capacity of traditional optical networks.Both optical access and optical interconnection are fiber-optic communication-based medium and short-distance fiber-optic communication networks.In the development process,multiple modulation methods and multiple service bearers are used to meet the increasing bandwidth requirements;it is developing in the direction of high speed,large capacity,and intelligence as well as high security.In the future,optical access and optical interconnection will mainly utilize multi-dimensional high-order optical modulation,which leads to relevant signal processing technologies with features such as high speed,low energy consumption,high efficiency,flexibility,and intelligence.However,there are still some problems such as electronic rate bottlenecks,excessive energy consumption,poor self-adaptability,low efficiency and no transparence of signal formats and bandwidth etc.in the traditional signal processing technology,which make it hard to meet the requirements of optical access and optical interconnection.Therefore,it is of great significance to explore and study the signal processing technology in optical access and optical interconnection,and it is also a difficult and hot topic in current optical network research.This thesis aims at the difficulties and needs of optical signal processing technologies in optical access and optical interconnection,and explores the optical signal processing technologies and digital signal processing technologies in optical access and optical interconnection.Supported by National Natural Science FONUdation of China(NSFC),Doctoral Fund of Ministry of Education of China and America National Science FONUdation(NSF),this thesis focuses on the above-mentioned technologies.Several technical schemes are proposed.The main research achievements and contributions are summarized as follows:Firstly,in order to enhance the security of the optical access and optical interconnection node services at the physical layer,an optical domain encryption/decryption method based on the secondary four-wave mixing(FWM)effect of semiconductor optical amplifiers(SOA)to realize high-order modulation signals is proposed.The simulation results show that the scheme can encrypt/decrypt octal phase shift keying(8PSK)signals in the optical domain,which provides an effective method for secure transmission of services at the physical layer in optical switching nodes.Secondly,aiming at the security problem of transmitting multiple high-order modulated optical signals in parallel in optical access and optical interconnection,a non-degenerate four-wave mixing(FWM)-based multi-channel multi-dimensional signal parallel non-key scheme is proposed.The simulation results show that this scheme can effectively realize the encryption/decryption process of three parallel signals,and does not require additional key signals,and the power cost of the encryption process is less than 1.5dB.It can provide an effective method for the secure transmission of services at the physical layer in optical switching nodes,and also provide an important guarantee for optical network security.Thirdly,focusing on the difficulty of clock extraction in high-speed optical access and optical interconnection,an ONU clock extraction scheme based on FP filter in WDM-PON is proposed.The simulation results show that this scheme can realize optical domain clock extraction of ONU high-speed 25Gbps signal;meanwhile,in order to overcome the problem of backward Rayleigh scattering interference between uplink and downlink signals,this scheme can carry on the wavelength transformation of the light domain through the XGM effect in SOA,it can realize the wavelength transformation and clock extraction function at the ONU end at the same time.Fourthly,in order to compensate for various physical damages of signals in mmw-RoF systems,a nonlinear detector based on SVM is proposed.After theoretical analysis and experimental verification,this solution can effectively suppress the nonlinear physical impairments of high-order modulation signals such as 16QAM,64QAM,16APSK,and 32ASPK.Compared with the classical DSP algorithm,this detector can improve the receiving sensitivity of the 64QAM signal with a bit rate of 2.4Gbps by nearly 2dB.Fifth,in order to mitigate various signal impairments in the mmw-RoF multi-service fusion transmission system,three parameter-free estimation and adaptive nonlinear detectors based on machine learning are proposed.The three algorithms have their own characteristics and are suitable for suppressing different types of signal physical damages.They all have intelligent learning ability and self-adaptive ability to solve the problem of flexible and variable damage of high-order modulation signals in the multi-service fusion transmission of mmw-RoF.