基于电流自适应补偿的高稳定度调制光栅Y分支型激光器控制系统

High-stability MG-Y Laser Control System Based on Self-adaptive Current Compensation

针对半导体激光器在实际应用中波长、功率稳定性较差以及控制系统复杂等问题,设计了一套高稳定度调制光栅Y分支型激光器控制系统。该系统利用模糊比例-积分-微分控制算法稳定功率,并通过两次正交试验优化算法参数,减小功率超调量,同时提出电流自适应补偿的波长校准算法,提升不同功率下的波长稳定性,解决电流内环反馈时引起的波长和功率交叉影响问题。结果表明,仿真优化后的激光器功率超调量从1.528%降低至0.014%,系统调整次数由21减小至17;测试调制光栅Y分支型激光器60 min内的功率漂移量仅为0.0044 mW,稳定度达到0.0604%,波长漂移量为1.9 pm,稳定度达到1.22×10^(−6)。经校准,激光器的半导体光放大器电流在28~78 mA范围内,波长变化量从23.4 pm减小至2.6 pm。

The output stability of semiconductor lasers is simultaneously affected by current and temperature,and the power and wavelength of lasers are prone to fluctuations in practice,which may even damage lasers permanent.In this paper,a high-stability Modulated Grating Y-branch(MG-Y)laser control system based on self-adaptive current compensation is proposed to address the problems of poor stability of wavelength and power as well as the complexity of the laser control system.The whole system is integrated into a printed circuit board with a small size,light weight and low power consumption.Based on the current inner loop feedback,we optimize the parameters of Fuzzy Proportional-Integral-Differential(PID)algorithm by orthogonal experiments and propose a wavelength calibration algorithm based on self-adaptive current compensation.The high-stability MG-Y laser control system is described in detail.Firstly,we introduce the system device and principle of operation.MG-Y laser is controlled by 5 currents and operates at 25℃.Left reflector current(Ileft),right reflector current(Iright),and phase section current(Iphase)are used for wavelength adjustment,while the power is adjusted by the gain section current(Igain)and the semiconductor optical amplifier current(ISOA).The control system is mainly composed of MG-Y laser,constant current source chip ADN8810,temperature control chip ADN8834,and operational amplifier chip AD8620.Secondly,in terms of power stability,a Fuzzy PID control parameter optimization algorithm based on orthogonal experiments is proposed to reduce both the overshoot of laser power and adjustment times of control system.The number of orthogonal experiments and the range of Fuzzy PID parameters need to be confirmed,then we design the orthogonal tables by screening the value range of each control parameter.The algorithm can effectively approach the optimal value of each parameter and also improve the performance of the laser control system.In the wavelength calibration part,we propose a wavelength calibration algorithm based on self-adaptive current compensation to reduce the central wavelength drift of MG-Y laser at different power levels.The algorithm takes advantage of the wavelength fine-tuning characteristics of the phase section current Iphase,by adjusting Iphase from 0 to 7.5 mA,continuous tuning of wavelength in the range of about 0.3 nm is possible.After setting a standard wavelengthλ,the Iphase region with stable wavelength variation and broad coverage is selected as linear compensation data region.ISOA scans in 1 mA steps until the range of the laser output power is fully covered,while the calibrated wavelengthλ*is obtained by updating Iphase according to the compensation data region so thatλ*is infinitely close toλ.We establish the look-up table for ISOA and Iphase and also fit the data in the table into segments.When the laser changes its power,the system adaptively calculates the corresponding Iphase according to ISOA and sets the wavelength to the standard wavelengthλadaptively.The algorithm solves the cross-influence problem between wavelength and power caused by current inner loop feedback,and improves the output stability of the MG-Y laser.The simulation and test results of the whole laser control system are shown at last,including the laser output power stability and wavelength drift.First,the performance of Fuzzy PID parameters optimization algorithm based on orthogonal experiments is simulated,and the results show that the overshoot of the laser power is reduced from 1.528%to 0.014%after optimization,and adjustment times of control system are lowered from 21 to 17.Then,we test the performance of MG-Y laser,and the results are almost consistent with the simulation results.The power stability is measured by the optical power meter PM400 and integrating sphere probe S145C.Before power stabilization,the output power fluctuation of 3000 samples(about 60 min)is 0.0219 mW,and the stability is 0.2698%.In comparison,the maximum fluctuation of laser power is 0.0044 mW,and the stability can reach 0.0604%in 60 min after stabilization.Finally,the wavelength stability is measured by fiber Bragg grating analyzer FBGA.The wavelength drift is 1.9 pm within 60 min.After wavelength calibration,the wavelength drift at different power levels is reduced from 23.4 pm to 2.6 pm at 1559.68 nm.In order to verify the accuracy of the wavelength calibration method,the output wavelength of the laser is increased from 1531 nm to 1569 nm with a step of 1 nm,and the output spectrum of the MG-Y laser was collected by spectrometer AQ6370D.Before wavelength calibration,the wavelength fluctuated at 1553 nm and 1555 nm where the drifts were as high as 91 pm and 76 pm respectively.After wavelength calibration,the wavelength drifts at 1553 nm and 1555 nm are lowered to 2 pm and 1 pm separately.The stability of wavelength under different output power is greatly improved.The simulation and test results show that the laser control system has excellent control capability and expands the application scenarios of MG-Y laser.