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

Abstract

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. Based on the existing laser heterodyne radiometer, this paper reports a prototype of nearinfrared laser heterodyne radiometer based on the erbium-doped fiber amplifier that can realize local oscillator power locking. The laser heterodyne radiometer uses a distributed feedback semiconductor laser with a center wavelength of 1.603 μm as the local oscillator light source. The erbium-doped fiber amplifier is used to amplify the local oscillator power, and the automatic power control circuit is used 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 measurement of the whole layer atmospheric transmittance spectrum without baseline fitting is realized. The instrument performance of a highly integrated laser heterodyne radiometer based on an erbium-doped fiber amplifier was evaluated in detail, and the atmospheric CO<sub>2</sub> transmittance spectrum was measured in the Science Island (31.9 ° N, 117.2 ° E) of Hefei. Six groups of atmospheric CO<sub>2</sub> transmittance spectra were obtained during the measurement period of one day, which were 17 compared with the simulation results of atmospheric radiation model, and the measurement results were consistent. The experimental results show that the application of erbium-doped fiber amplifier enhance the performance of laser heterodyne radiometer, optimize its structure, and provide equipment supplement for realizing unattended long-term atmospheric CO<sub>2</sub> concentration observation and building a comprehensive carbon observation network.