Dual-logarithmic demodulation method application in a wide gas optical thickness range

Direct absorption spectroscopy (DAS) is an extremely practical and effective technology to detect gas concentration in site applications. Dual-beam subtraction is one of the most common demodulation methods in DAS, yet this method cannot solve the problem of absolute absorption curve nonlinearizatio...

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Bibliographic Details
Published in:Applied optics (2004) 2021-09, Vol.60 (26), p.8206
Main Authors: Zhang, Zhifeng, Chang, Jun, Sun, Jiachen, Zhang, Qinduan, Fan, Yongmei
Format: Article
Language:English
Subjects:
Acetylene
Demodulation
Linearity
Meteorological satellites
Optical thickness
Subtraction
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Summary:Direct absorption spectroscopy (DAS) is an extremely practical and effective technology to detect gas concentration in site applications. Dual-beam subtraction is one of the most common demodulation methods in DAS, yet this method cannot solve the problem of absolute absorption curve nonlinearization in a wide optical thickness range. A real-time and practical dual-logarithmic demodulation method is proposed and proved to be robust when the optical thickness is much greater than linear region. Moreover, the error of optical thickness peak is only 1.18% between the dual-logarithmic demodulation system and simulation after correcting the dual-beam subtraction demodulation system under a 300 K, 1 atm, and 3 m absorption path. When the range of optical thickness peak of acetylene is from 0.0252 to 2.5335 at 1532.83 nm, the peak voltages always maintain satisfactory linearity ( R - s q u a r e = 0.9989 ).
ISSN:1559-128X
2155-3165
DOI:10.1364/AO.433294