Research On Frequency Modulation Linearization Of Current-tuned DFB Laser

FMCW LiDAR has become a hot research topic due to its lower working power,higher resolution and immune background light,but it requires the light source to be able to output the laser with continuous linear frequency modulation.The tunable semiconductor Laser has gradually become a potential ideal light source for FMCW LiDAR due to its flexible direct current tuning characteristics,high reliability,good monochromator and low noise,and its simple structure,low price and wide application.But the technology of laser frequency modulation linearization is particularly important,because the semiconductor laser itself has frequency modulation nonlinearity.This paper mainly focuses on the research on frequency modulation linearization of current-tuned DFB laser.Influence of nonlinear of linear FMCW source on FMCW LiDAR ranging is analyzed briefly and the simulation test of FMCW LiDAR ranging is carried out.The principle of injection current tuning in DFB laser and the reason of frequency modulation nonlinearity are introduced,and then the influence of frequency modulation nonlinearity on the frequency of beat signal is explained.This paper briefly introduces the principles of different frequency modulation linearization methods and their advantages and disadvantages.By analyzing these theories,a frequency modulation linearization scheme is proposed and designed.After analyzing the scheme in detail,a high-pass filter for amplitudefrequency response is designed,and the simulation verification of the scheme is prepared.Each simulation module is designed and parameters are set,and different schemes are proposed for envelope signal extraction.The envelope extraction scheme was simulated and compared,the scheme of extracting the envelope with envelope algorithm is determined.Finally,the frequency modulation linearization simulation experiment platform was built for verification and analysis.The designed frequency modulation linearization scheme based on amplitude-frequency response is used for simulation,and the simulation results are compared and analyzed in detail.The results show that compared with the uncorrected nonlinear beat signals,the spectrum distribution of the feedback corrected beat signals is more concentrated and tends to be ideal.By quantitative analysis of the frequency modulation curve,the frequency linearity of the primary feedback correction is improved nearly 9 times.The scheme itself has some problems such as residual nonlinearity and non-real-time,but there is still room for improvement.It is believed that the scheme will have better application after further study.