本振光功率锁定方法应用于激光外差辐射计的研究

Research on application of local oscillator power locking method to laser heterodyne radiometer

激光外差辐射计具备成本低、体积小、光谱分辨率高等优势,可扩展现有的地面碳测量网络,验证卫星观测结果,并能在卫星观测区域外提供数据覆盖.本文在现有的激光外差辐射计的基础上,报道了基于掺铒光纤放大器的可实现本振光功率锁定的近红外激光外差辐射计原型机.该激光外差辐射计利用一个中心波长为1.603μm的分布反馈式半导体激光器作为本振光源,采用掺铒光纤放大器放大本振光功率,并利用自动功率控制电路实现掺铒光纤放大器输出端光功率的锁定,消除了由本振光功率变化引起的基线斜率,从而实现免基线拟合的整层大气透过率谱的测量.详细评估了基于掺铒光纤放大器的高度集成化的激光外差辐射计的仪器性能,并在合肥市科学岛(31.9°N, 117.2°E)地区进行了整层大气CO_(2)透过率谱的测量.在一天的测量时间内得到6组大气CO_(2)透过率谱,与大气辐射模型模拟结果进行比对,测量结果一致.实验结果表明,掺铒光纤放大器的应用可以提高激光外差辐射计的性能,优化其结构,进而为实现无人值守的长期大气CO_(2)浓度观测和构建全面的碳观测网络提供仪器设备的补充.

Laser heterodyne radiometer has the advantages of low cost,small size,and high spectral resolution.It can expand the existing ground carbon measurement network,verify satellite observation results,and provide data coverage outside the satellite observation area.Using the existing laser heterodyne radiometer,is presented a prototype of near-infrared laser heterodyne radiometer based on the erbium-doped fiber amplifier that can realize local oscillator power locking.In the laser heterodyne radiometer a distributed feedback semiconductor laser with a center wavelength of 1.603μm is used as a local oscillator light source.The erbium-doped fiber amplifier is used to enhance the local oscillator power,and the automatic power control circuit is adopted to lock the output optical power of the erbium-doped fiber amplifier.The baseline slope caused by the change of the local oscillator power is eliminated,and the whole layer atmospheric transmittance spectrum without baseline fitting is measured.The instrument performance of a highly integrated laser heterodyne radiometer based on an erbium-doped fiber amplifier is evaluated in detail,and the atmospheric CO_(2) transmittance spectrum is measured in the Science Island(31.9°N,117.2°E)of Hefei.Six groups of atmospheric CO_(2) transmittance spectra are obtained during the measurement period of one day,which are compared with the simulation results from an atmospheric radiation model,showing that they are consistent with each other.The experimental results show that the application of erbium-doped fiber amplifier can improve the performance of laser heterodyne radiometer,optimize its structure,and provide equipment supplement for realizing unattended long-term atmospheric CO_(2) concentration observation and building a comprehensive carbon observation network.