30 November 2011 Research on reduction of long-term distortions and suppression of light intensity fluctuations in a TDLAS system
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Proceedings Volume 8201, 2011 International Conference on Optical Instruments and Technology: Optoelectronic Measurement Technology and Systems; 82010H (2011); doi: 10.1117/12.910065
Event: International Conference on Optical Instruments and Technology (OIT2011), 2011, Beijing, Beijing, China
Abstract
For any tunable diode laser absorption spectroscopy (TDLAS) system, its performance is often degraded by long-term distortion and fluctuations of light intensity. The source of long-term distortion and the corresponding proposal are discussed at first in this paper. It is proved that the long-term distortion of the system is mainly induced by the change of wavelength dependent transfer function. A balanced optical path can be used to reduce it effectively. In order to decrease the disturbance of intensity fluctuation, a novel method for online correction is presented. It is developed according to the linear relation between the peaks of harmonic power spectra and the incident light intensity. It is demonstrated by the experiments and explained as residual sum frequency and difference frequency power of signal and reference after the lock-in amplifier. This method could achieve real-time light intensity correction with only little calculation. By using a 17.5m multi-pass cell, the experiments show that the system can achieve about 20ppmv stability for long-term continual monitoring. Allan variance indicates that the detection limit for short-term measurement is between 0.3ppmv and 1.5ppmv depending on the response time allowed by the instrument.
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Guo-jie Tu, Yu Wang, Feng-zhong Dong, "Research on reduction of long-term distortions and suppression of light intensity fluctuations in a TDLAS system", Proc. SPIE 8201, 2011 International Conference on Optical Instruments and Technology: Optoelectronic Measurement Technology and Systems, 82010H (30 November 2011); doi: 10.1117/12.910065; https://doi.org/10.1117/12.910065
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KEYWORDS
Absorption

Modulation

Signal detection

Singular optics

Carbon monoxide

Digital signal processing

Semiconductor lasers

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