转动拉曼激光雷达大气温度绝对探测技术研究

The rotational Raman lidar is a valid tool and method for detecting atmospheric temprature. But the fact that its using for measuring atmospheric temprature needs generally to a certain collocated device for calibration seriously restricts its application progress in the meteorology and environmental monitoring fields. The absolute detection technique of the rotational Raman lidar for atmospheric temprature are researched in this project using the dependence of rotational Raman spectral envelope on temprature. We use the fiber Bragg grating in the visible wavelength having sucessfully been studied and fabricated as the core device, and integrate the superiority of the conventional diffraction grating. We mainly research the key techniques and methods such as the two-stage multi-channel parrlel rotional Raman spectroscopic technique and the custom-made fiber-line-array optical coupling technique, the technique of the multi-spectra-line real-time separating the weak rotational Raman spectra-line under the intensive background condition and the multi-channel real-time detecting the rotational Raman optical signal, the fit method of the rotational Raman spectral envolope and the absolute retrieve algorithm for atmospheric temprature. The experimental verification research is executed to implement the absulte detection techinique of the rotational Raman lidar for atmospheric temprature. This research incorporates the latest technologies of modern fiber sensing and laser remoting-sensing. Its results will provide a newly design scheme and method for the detecting with accuracy of the Raman lidar for the atmospheric temprature profile and the techical support for application progress.

转动拉曼测温激光雷达是大气温度探测的有效手段及方法，但转动拉曼激光雷达探测大气温度一般需要其它并行设备对系统进行校正的问题，严重制约其在气象及环境监测领域中的实用化进程。本项目提出利用大气分子转动拉曼谱型与温度之间的依赖关系，研究转动拉曼测温激光雷达的大气温度绝对探测技术。以最新研制成功的可见光波段窄带光纤Bragg光栅为核心器件，结合传统衍射光栅的空间分光优势，重点研究两级多路并行转动拉曼分光技术和特种光纤线阵列光信号转接耦合技术，强背景条件下的微弱转动拉曼散射谱线的多谱线实时分离、多路并行转动拉曼信号光实时检测，以及转动拉曼散射谱线的谱型拟合，大气温度的绝对反演算法等关键技术与方法，并开展实验验证研究，以期实现转动拉曼激光雷达的大气温度绝对探测技术。研究融合现代光纤传感和激光遥感等新技术，其成果可为拉曼激光雷达准确探测温度廓线提供新的设计思路及方法，为实用化研发提供技术支撑。

目前转动拉曼测温激光雷达已成为大气温度探测的最有效手段及方法之一，通常采用两路转动拉曼回波信号反演大气温度廓线，系统正常运行需要其它并行设备对系统参数进行校正，严重制约其在气象及环境监测领域中的实用化进程。本项目利用大气分子转动拉曼谱型与温度之间的依赖关系，研究转动拉曼测温激光雷达的大气温度绝对探测技术。以课题组研制成功的可见光波段窄带光纤Bragg光栅为核心器件，结合传统衍射光栅的空间分光优势，研究多转动拉曼信号光谱分离、多路并行转动拉曼信号光实时探测，以及大气温度的绝对反演算法等关键技术。.以光栅的严格耦合波理论为基础，优化闪耀光栅参数，设计单模光纤线阵列的结构，结合接收单模光纤460-HP参数，优化选择了531.01、530.11、529.66、528.76、527.86、527.42nm六条谱线进行大气温度直接反演，并基于500 nm闪耀波长的一阶衍射光栅，设计了多通道转动拉曼信号分光光路，分析了基于单模光纤转接的结构及装配公差。基于线阵光电倍增管设计了高效多通道并行微弱光信号探测系统，从光谱响应一致性，实际耦合效率和对米-瑞利信号的抑制率三个方面，验证了所设计的光电探测系统与理论分析具有很好的一致性，且其带外抑制率达到约30 dB，验证了分光及探测方案的可行性。以最小二乘原理为核心，研究了基于玻尔兹曼函数和瑞利函数的大气温度直接反演算法，对比分析了利用6条转动拉曼后向散射截面强度直接反演大气温度的效果，表明瑞利函数与玻尔兹曼函数所对应相同温度下的包络线的半高宽（FWHM）之间的平均相对误差小于2%，验证了瑞利函数反演大气温度的可行性以及有效性。系统仿真和实验研究表明，可实现晚上温度探测高度为3 km，绝对测温激光雷达系统通过提取多条拉曼谱线可用于探测大气温度廓线，可为大气温度的高精度激光遥感探测提供新的校正方法。