差分吸收相干激光雷达中偏振分集技术研究

为减小差分吸收相干激光雷达(DIAL)中偏振衰落对 回波信号功率反演精度影响,研究了偏振分集技术(PDT)在相干DIAL中 的作用,构建了利用STM32控制的双光束切换DIAL实验装置。依托构 建的装置,利用平衡探 测,分别采用PDT和一般外差探测完成多组次实验,应用单频检测方法得到20m光程下吸收 气体不同浓度下相干中频信号的振 幅值,并由此求解出on光和off光回波信号功率。对回波信号功率值差分信息与由HITRAN得 到的参考差分信息比较 发现:应用PDT能使探测分辨率提高4倍,对应到2km距离内,可以探测到3.5×10－6ppm的CO₂浓度变化,满足了 气候研究所需的优于1％的精度要求,验证了PDT消除偏振衰落以及提高相干DIAL分辨精度的 作用。

Research on polarization diversity technology in coherent differential absorptio n lidar

To reduce the impact of polarization- induced fading in coherent differential absorption lidar (DIAL),the basic princi ple of polarization diversity technology (PDT) is studied in a coherent lidar syste m.A dual-wavelength switching DIAL system controlled by STM32is performed.Based on the system,many groups of experiments with balanced detection are conducted using PDT and normal heterodyne detection respectively,and the amplit udes of intermediate frequency (IF) are acquired in different concentrations in an optical path of 20m with single freq u ency detection.And the return power of on light and off light could be solved from these amplitudes of IF.By comparing th e differential information of the return signal power with the reference differential value acquired from the HITRAN database,i t is indicated that the minimum concentration the system could detect with PDT is improved by 4times than those without PDT,and thus a variation of 3.5mg/L o f CO_{2concentration} could be identified corresponding to a range of 2km,which could meet the need of climate research with the requirement of verifying the concentration change of better than 1%.The effects of PDT on eliminating polarization-induced fading and improving the resolution of DIAL detection are verified,which is im portant to the research of DIAL.