High Order Modulated Optical Signal Distortion Evaluation And Compensation Technology For Coherent Optical Communication

At present,the development direction of optical fiber communication is to evolve to the technical line of ultra-high-speed ultrahigh spectral efficiency.The application of technologies such as high modulation rate and high-order modulation format will increase the transmission capacity of the communication and also impair the optical signal distortion More sensitive.This dissertation focuses on the design of coherent optical communication system,the evaluation of high-order optical signal distortion and the compensation of received signal damage.An experimental system of coherent optical communication that can dynamically adjust the key parameters is designed.The optical emission Machine signal distortion assessment method and the optical transceiver damage signal compensation technology,through the use of mathematical simulation and experimental verification of a combination of means to verify the performance of coherent optical communication system experiment and signal distortion assessment study to verify the signal evaluation method and the damage compensation algorithm effectiveness.In the design of coherent optical communication experiment system,prototype design of three parts of tunable laser source,single/dual polarization transmitter and coherent receiver was completed.In single/dual polarization transmitter designs,the amplifier gain and offset voltage of the multiplexed baseband signal are independently adjustable to avoid imbalance distortion of the phase/quadrature(I/Q)gain of the optical transmitter signal Problems,while optimizing the design of the power supply circuit to improve the work of single/dual polarization transmitter stability.In the design of coherent optical receiver,it can realize the coherent reception of single/dual polarization signals,with automatic/manual gain control switching and acquisition bandwidth adjustment function to ensure the coherent receiver to meet the best acquisition performance of different signals.In the research of high-order modulated optical signal distortion estimation,a new algorithm is proposed in the dual-link system with the same length of signal light and local optical link,using K-means clustering algorithm and blind phase estimation(BPS)Algorithm for accurate distortion coefficient estimation and constellation recovery method.The system must ensure that the lengths of the local oscillator light and signal light transmission links are substantially equal so that the phase difference between the signal light and the local oscillator light is approximately constant over a certain time window and therefore the poly Class analysis,the two-dimensional position of the cluster centroid can be calculated to estimate the type of distortion and the distortion coefficient.In addition,the subsequent channel equalization and carrier phase recovery also take the clustered centroid point as the reference point.This scheme avoids the problem of signal recovery in the presence of signal distortion and phase noise,and accurately estimates the distortion of the optical signal in the high-order modulation format.Aiming at the problem of distorted damage to the received signal,the performance of the traditional Gram-Schmidt orthogonalization(GSOP)algorithm and the blind adaptive source-free constant modulus algorithm/radius decision equalizer(BASS-CMA /RDE),Proposed a blind adaptive source separation-extended Kalman algorithm(BASSEKF)algorithm has better damage compensation performance.Because of the limitations of the GSOP algorithm which can not compensate for I/Q gain imbalance damage and are not suitable for the case of frequency offset existing in the system,the BASS-CMA/RDE algorithm has the disadvantages of slow convergence and singularity in solution bias.In this paper,BASS The combination of I/Q imbalance compensation and EKF polarization demultiplexing can both improve the convergence rate of depolarization and make the performance of I/Q imbalance compensation more excellent.The results of this paper are of great reference significance for the research of coherent optical communication experiment system and prototype,meanwhile the duallink experiment system and K-menas clustering algorithm evaluate the signal quality of optical transmitter and put forward a new method which can simplify the difficulty of experimental data processing However,the BASS-EKF algorithm can achieve the joint recovery of I/Q imbalance compensation and polarization demultiplexing in the received signal,and the ideal constellation is obtained.The subject of the transmitter module performance testing,distortion assessment,damage compensation and other practical applications of great significance.