全光纤双通道大气温室气体激光外差光谱探测技术研究

Research on All-Fiber Dual-Channel Atmospheric Greenhouse Gases Laser Heterodyne Detection Technology

激光外差光谱技术是近年迅速发展的一种高光谱分辨率遥感探测技术,其装置具有体积小、光谱分辨率高等特点,适用于大气温室气体浓度的探测。各种观测实验已证明其是一种切实、有效的探测手段,在地球大气探测领域具有很大的应用前景和潜力。在现有激光外差光谱仪器的基础之上,提出了一种新型的仪器结构。采用光纤光开关对直射的太阳光进行调制与分束,实现利用单个光纤光开关进行两个波段激光外差信号的同时探测。为全光纤激光外差光谱仪的下一步系统集成和多波段激光外差光谱仪的构建提供了新方法。从激光外差探测的原理出发,分析了激光外差光谱探测技术的优势和关键参数,并结合自行研制的高精度太阳跟踪仪,搭建了一套近红外双通道全光纤式激光外差辐射计的原理样机。详细地阐述了激光外差辐射计原理样机中各功能模块的作用和参数,着重描述了光纤光开关在其中的作用原理和功能,详细地讨论了激光外差光谱仪的波长扫描模式和波长标定方法。在此基础上,讨论了激光外差辐射计的相关参数设置依据和仪器函数的测量方法,并给出了激光外差装置的仪器函数以及相应的光谱分辨率(0.0044 cm^-1)。利用搭建的激光外差光谱仪在合肥地区(31.9°N,117.166°E)进行了实际的大气探测,同时在波段(6056.2~6058.1 cm^-1)和(6035.6~6036.5 cm^-1)分别获取了CH 4和CO 2分子的激光外差吸收信号,并对吸收信号进行了波长标定和归一化,得到了CH 4分子和CO 2分子的整层大气透过率谱,测量光谱信号的信噪比分别为197和209,同时也对分子吸收信号的光谱特征进行了分析。本文的测量实践表明光纤光开关可以用于激光外差光谱系统的结构优化,实现多通道多波段的激光外差光谱同时测量,拓展激光外差光谱仪在大气探测领域的应用。

Laser heterodyne spectroscopy is a high-resolution remote sensing detection technology developed rapidly in recent years.Its device has the characteristics of small size,high spectral resolution,and is suitable for the detection of the concentration of atmospheric greenhouse gases.At present,it has been proved to be a practical and effective detection method in various observation experiments and has great application prospects and potentials in the field of earth atmosphere detection.Based on the existing laser heterodyne spectroscopy instruments,a new instrument structure is proposed in this paper.A fiber optic switch was used to modulate and split the direct sunlight,and realize the simultaneous detection of two-band laser heterodyne signals.It provides a new method for the next system integration of all-fiber laser heterodyne radiometer(LHR)and the construction of multi-band LHR.Based on the principle of laser heterodyne detection,this paper analyzes the advantages and key parameters of laser heterodyne spectrum detection technology.Combined with a self-developed high-precision solar tracker,a set of principle prototypes of a near-infrared dual-channel all-fiber LHR was built.The functions and parameters of the functional modules in LHR are elaborated in detail.The function principle and function of fiber optic switch are emphasized.The wavelength scanning mode and wavelength calibration method of the LHR are discussed.Based on this,the setting basis of related parameters and measurement method of the instrument function is discussed,and the instrument functions and the corresponding spectral resolution(0.0044 cm^-1)of the LHR described in this paper are given.Using the built LHR to conduct actual atmospheric surveys in the Hefei area(31.9°N,117.166°E),the laser heterodyne signals of CH4 and CO2 in the band of(6056.2~6058.1 cm^-1)and(6035.6~6036.5 cm-1)were obtained simultaneously.The wavelength calibration and normalization of the absorption signals were performed to obtain the entire atmospheric transmittance spectrum of CH4 and CO2 molecules in the atmosphere.The signal-to-noise ratios of the measured spectral signals are 197 and 209,respectively and the spectral characteristics of molecular absorption signals are analyzed.The measurement practice in this paper shows that the fiber optical switch can be used to optimize the structure of laser heterodyne spectroscopy system,achieve the simultaneous measurement of multi-channel and multi-band LHR,and expand the application of LHR in the field of atmospheric detection.