title: Performance improvement and analysis of a 1.6 μm continuous-wave modulation laser absorption spectrometer system for CO2 sensing.
abstract: In a previous study, we developed a 1.6 μm continuous-wave (cw) modulation laser absorption spectrometer system for CO(2) sensing and demonstrated the measurement of small fluctuations in CO(2) corresponding to a precision of 4 parts per million (ppm) with a measurement interval of 32 s. In this paper, we present the process to achieve this highly specific measurement by introducing important points, which have not been shown in the previous study. Following the results of preliminary experiments, we added a function for speckle averaging on the optical antenna unit. We additionally came up with some ideas to avoid the influences of etalon effects and polarization dependence in optical components. Because of the new functions, we realized a calibration precision of 0.006 dB (rms), which corresponds to a CO(2) concentration precision of less than 1 ppm for a 2 km path. We also analyzed the CO(2) sensing performance after the improvements described above. The measured short time fluctuation of the differential absorption optical depth was reasonably close to that calculated using the carrier-to-noise ratio of the received signal.
authors.affiliation: Information Technology R&D Center, Mitsubishi Electric Corporation, 5-1-1 Ofuna, Kamakura, Kanagawa, Japan 247-8501. Kameyama.Shumpei@dn.MitsubishiElectric.co.jp
authors.forename: Shumpei
authors.initials: S
authors.lastname: Kameyama
authors.forename: Masaharu
authors.initials: M
authors.lastname: Imaki
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Hirano
authors.forename: Shinichi
authors.initials: S
authors.lastname: Ueno
authors.forename: Shuji
authors.initials: S
authors.lastname: Kawakami
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sakaizawa
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Nakajima