We demonstrate a new design hollow optical fiber suitable for use on IR heterodyne spectroscopy in mid-infrared wavelength region. The spectral feature of the laser emission line and the system noise temperature obtained by heterodyne detection with hollow optical fiber is confirmed by a laboratory measurement. The system noise temperature less than 3000 K obtained by the experimental setup with the CO2 laser-based heterodyne system led by a hollow optical fiber is only ~100 % above the quantum limit. The hollow optical fiber allows heterodyne detection with a sufficient efficiency. This permits simplified fabrication, provides even more weight reduction. Further investigation is required for use of hollow optical fiber on the target source.
Remote sensing of the atmospheric greenhouse gases, methane (CH4) and carbon dioxide (CO2), contributes to the understanding of global warming and climate change. A portable ground-based instrument consisting of a commercially available desktop optical spectrum analyzer and a small sun tracker has been applied to measure the column densities of atmospheric CH4 and CO2 at Yanting observation station in a mountainous paddy field of the Sichuan Basin from September to November 2013. The column-averaged dry-air molar mixing ratios, XCH4/XCO2, are compared with those retrieved by satellite observations in the Sichuan Basin and by ground-based network observations in the same latitude zone as the Yanting observation station.
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