A Research Of Adaptive Digital Backpropagation Compensation Algorithm For Coherent Optical Communication System

With the deepening of social informatization,the mass data generated by human society is growing rapidly,and people's demand for the transmission rate of optical communication system is also growing.Coherent optical communication can realize high frequency partial efficiency transmission by using high order modulation format.In coherent optical communication,signals can be mapped from optical domain to electrical domain by means of coherent detection.At present,digital signal processing can completely compensate the linear damage of optical signal in the transmission process of optical fiber link,but the compensation for nonlinear damage is still in the stage of perfection.Based on the single carrier coherent optical transmission system and the general digital back propagation algorithm,the adaptive digital back propagation compensation algorithm is further carried out.The main research work of this paper is as follows:1.This paper studies the nonlinear compensation algorithm of digital back propagation(DBP),and then designs an adaptive digital back propagation algorithm(A-DBP)suitable for 16 QAM.This algorithm is based on a cost function of using amplitude information,and uses golden section search method to optimize the estimation of nonlinear coefficient.Compared with ordinary DBP algorithm,the A-DBP algorithm proposed in this paper can compensate the nonlinear damage to the signal without knowing the nonlinear coefficient.2.In order to verify the nonlinear compensation effect of A-DBP proposed in this paper,a single-polarization and dual-polarization coherent optical transmission simulation platform was built,which was used for long distance optical transmission simulation of 12.5GBaud 16 QAM.The performance of A-DBP proposed in this paper is verified by using single polarization and double polarization data respectively.The simulation results show that the proposed algorithm can achieve further performance improvement,obtain greater signal-to-noise ratio and bit error rate gain on the basis of ordinary DBP algorithm,and further improve the optimal launch optical power.3.Based on the completion of simulation verification,this paper further carried out 16 QAM 12.5G single carrier single polarization and 12.5G single carrier dual polarization coherent optical transmission experiments,and verified the experimental performance of A-DBP with experimental data.Experiments show that compared with the linear equalization method,the A-DBP proposed in this paper can obtain significant signal-to-noise ratio and bit error rate gain under the condition of high launch optical power,and at the same time can greatly improve the optimal launch optical power.