Research On Nonlinear Damage Compensation In Coherent Optical Communication System

With the continuous progress and development of contemporary social networks,the rise of advanced technologies such as the Internet of Things,VR and cloud computing,people begin to have a higher and higher demand for the transmission rate and capacity of communication,which further promotes the emergence and development of various kinds of optical fiber communication related technologies.At present,optical fiber communication is developing to aim at larger transmission capacity,higher transmission rate and lower time delay.With the development of the research in the field of coherent optical communication,the processing speed of DSP hardware is constantly improving.The coherent optical communication system,which adopts a variety of modulation and coding formats at the sending end and coherent detection technology at the receiving end and the combination of DSP,has become one of the key technologies in the field of high speed and large capacity optical communication.In the high speed and large capacity coherent communication system,the nonlinear effect in the fiber channel seriously affects the transmission quality of the signal,which is considered to be one of the main reasons for limiting the fiber transmission.It is very important to study how to compensate the nonlinear damage in the channel to improve the quality of coherent optical communication system.In this thesis,the key principle of nonlinear damage compensation technology in digital signal processing module is studied.On this basis,the nonlinear damage compensation scheme based on digital signal processing,the nonlinear damage compensation scheme based on digital signal preprocessing and the nonlinear damage compensation scheme based on Fourier transform are emphatically researched.The key work content and novelties in the whole thesis are as follows:(1)An adaptive DBP scheme based on the driving amount of adaptive gradient descent algorithm(AGDAM)is proposed.This scheme improves the convergence speed of the algorithm without reducing the convergence precision.In the single-carrier 64QAM coherent optical communication system,the performance of the scheme is simulated and studied.The parameters of AGDAM algorithm are optimized to improve the iteration speed of the algorithm,and the performance of the scheme is simulated.The results show that,compared with the traditional gradient descent algorithm,AGDAM has obvious benefits in terms of convergence speed.(2)A nonlinear compensation scheme based on the adaptive digital back propagation algorithm of the sender is proposed,which improves the flexibility of the algorithm while optimizing the performance of the communication system.The performance of the scheme is simulated and studied for 16QAM coherent optical communication system with single carrier,and the performance of the scheme is simulated.The results show that this proposed scheme can effectively suppress the nonlinear damage.Compared with the dispersion pre-compensation algorithm,this scheme improves the transmission performance of the communication system.(3)A nonlinear compensation scheme based on adaptive logarithmic step size is proposed,which improves the performance of the communication system without increasing the complexity of the algorithm.In QPSK coherent optical communication system,the feasibility of the scheme is verified by simulation,and the performance of the scheme is simulated.The results show that the proposed scheme can effectively suppress the nonlinear damage,and compared with the traditional DBP algorithm,the nonlinear damage compensation effect is better,and the signal transmission performance of the system is better.