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Sensors 2015, 15(4), 9582-9591; doi:10.3390/s150409582

Immunity to Laser Power Variation in a DFB Diode Laser Based Optical Gas Sensor Using a Division Process

School of Information Science and Engineering and Shandong Provincial Key Laboratory of Laser Technology and Application, Shandong University, Jinan 250100, China
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Author to whom correspondence should be addressed.
Academic Editor: Gary R. Pickrell
Received: 17 March 2015 / Revised: 16 April 2015 / Accepted: 16 April 2015 / Published: 22 April 2015
(This article belongs to the Special Issue Optical Sensors for Chemical, Biological and Industrial Applications)
View Full-Text   |   Download PDF [871 KB, uploaded 22 April 2015]   |  

Abstract

The division process used in a DFB diode laser-based optical gas sensor was studied to improve the immunity to laser power variation. Residual amplitude modulation (RAM) in wavelength modulation spectroscopy (WMS) detection was eliminated by intensity normalization using a division process. As a result the detected harmonic signals showed a significant improvement in line shape. For the first harmonic (1f) signal, Bias was improved from 38.7% to 1.2%; Baseline Difference was improved from 2.7% to 0.69% and Asymmetry was improved from 15.4% to 0.22%. For the second harmonic (2f) signal, the Asymmetry Coefficient was improved from 103% to 5.1%. Moreover the division process can further suppress the influence of unstable laser power. As a result, for the 1f signal, stable detection with a variation coefficient of 0.59% was obtained over a wide dynamic range (0.38–8.1 mW). For the 2f signal, stable detection with a variation coefficient of 0.53% was obtained from 0.64 mW to 8.27 mW. The test results showed a good agreement with the theoretical analysis and the proposed method has considerable potential application in gas sensing. View Full-Text
Keywords: optical gas sensor; division process; residual amplitude modulation; wavelength modulation spectroscopy; unstable laser power optical gas sensor; division process; residual amplitude modulation; wavelength modulation spectroscopy; unstable laser power
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Chang, H.; Chang, J.; Huang, Q.; Wang, Q.; Tian, C.; Wei, W.; Liu, Y. Immunity to Laser Power Variation in a DFB Diode Laser Based Optical Gas Sensor Using a Division Process. Sensors 2015, 15, 9582-9591.

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