Open AccessWavelength-locking-free 157µm differential absorption lidar for CO_2 sensing
Author(s) -
Hao Liu,
Tao Chen,
Rong Shu,
Guanglie Hong,
Li Zheng,
Yong Ge,
Yihua Hu
Publication year - 2014
Publication title -
optics express
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.22.027675
Subject(s) - lidar , optics , wavelength , laser , tunable diode laser absorption spectroscopy , materials science , absorption (acoustics) , dial , calibration , attenuation coefficient , tunable laser , remote sensing , physics , quantum mechanics , acoustics , geology
We propose a novel wavelength-locking-free differential absorption lidar system for CO₂ sensing. The ON-line wavelength laser was wavelength modulated around a specific CO₂ absorption line to ensure that the emission from the ON-line laser hit the atmospheric CO₂ absorption line peak twice a cycle. In the meantime, the intensity of the ON-line and OFF-line wavelength lasers were sinusoidally intensity modulated to enhance the SNR of the back-scattered signal. As a consequence, the system configuration was simplified and the measurement error caused by the deviation of CO₂ absorption coefficient from the long-time ON-line wavelength drifting was completely eliminated. Furthermore, a more precise calibration method was developed which could simultaneously calibrate the offset and precision of the lidar detector. This method could be applied to other differential-absorption-based lidar systems. The result showed that a measurement precision of 0.525% for the column concentration was achieved in 1 s time interval through a path of 780m. We recorded the CO₂ concentration variation for 12 hours starting from mid-night, the result showed that the course of the concentration derived from the DIAL was in good agreement with that of the in situ CO₂ sensor only when the status of atmosphere was stable.