Control Technology Of Semiconductor Laser Based On Digital Signal Synthesis

In recent years,with the continuous commercialization of optical communication,semiconductor laser-based optical carrier light source has been fully developed.Semiconductor lasers due to the characteristics of their own materials,linear interval exists second harmonic and third harmonic,seriously affected the optical information transmission.The nonlinear properties are mainly studied by means of rate equations or polynomial fitting methods.In order to compensate for nonlinear properties,pre-distortion are usually used to eliminate the second and third harmonics.This paper introduces the basic principle and related characteristics of semiconductor lasers,and designs the input current and output optical power acquisition system.The threshold current of the semiconductor laser is obtained by studying the P-I curve,and the existence of the nonlinearity is proved.In order to reduce the fitting error and filter out the noise using the lifting wavelet,select the threshold and the number of decomposition layers.The data are processed by MATLAB,and the laser polynomial is obtained.According to different characteristics of P-I double edge,the splicing method is designed.And using the mean square error and cross correlation to prove the effectiveness of the method fit the laser.A pre-distortion and laser fitting model is constructed.The P-I curve of the linearized laser can be proved by MATLAB simulation.In this paper,FPGA as a semiconductor laser modulation control unit,and the design of the overall structure of the FPGA.According to the top-down approach,the system is divided into coefficient calculation module,PLL module,memory module and call module four parts.Simulate the function of each module with Model Sim and compare the calculated values with the values calculated by MATLAB.The results show that the data calculated in FPGA can effectively guarantee the accuracy of four decimal places.Collect the data after adding the pre-distortion,compare it with the original data,and the results are consistent with the simulation results.