线性调频激光器是调频连续波(FMCW)激光雷达的核心器件,激光器的调频线性度影响FMCW激光雷达的测距精度和分辨率等参数性能.从抑制激光器的调频非线性出发,基于现场可编程门阵列(FPGA),设计以预失真迭代控制学习算法为核心的分布式反馈(DFB)激光器调频非线性校正系统.该系统能够实时检测激光器非线性度,并根据非线性失真情况实时优化激光器的注入电流,显著降低DFB激光器的调频非线性度.利用该方法实现在5 kHz的调制频率下,扫频带宽为1.2 GHz的线性调频DFB激光器.DFB激光器的上下扫频周期的非线性度由校正前的2.62%和1.96%分别降低到0.035%和0.031%.利用研制的线性调频DFB激光器进行测距实验,5 m内最大误差小于14 mm.
Real-Time Nonlinear Correction Technology of Linear Frequency Modulation Distributed Feedback Laser Based on FPGA
A linear frequency modulation laser is the core device of frequency modulated continuous wave(FMCW)lidar,and the frequency modulation linearity of the laser affects the ranging accuracy and resolution performance of FMCW lidar.This study first suppressed the frequency modulation nonlinearity of lasers and subsequently designed a distributed feedback(DFB)laser frequency modulation nonlinearity correction system based on a field programmable gate array(FPGA).Here,a pre-distortion iterative control learning algorithm acts as the core of the system.In real time,the system can detect the nonlinearity of the laser and optimize its injection current based on nonlinear distortion,thereby significantly reducing the frequency modulation nonlinearity of the DFB laser.A linear frequency modulation DFB laser with a scanning frequency of 5 kHz and a modulation bandwidth of 1.2 GHz is achieved using this method.The nonlinearity of the up and down sweep cycles of the DFB laser is reduced from 2.62%and 1.96%to 0.035%and 0.031%,respectively.Ranging experiments were conducted using the developed linear frequency modulation DFB laser,where the maximum error within 5 m is less than 14 mm.
linear frequency modulation lasernonlinear correctionfrequency modulated continuous wave lidarsemiconductor laser
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