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Immunity to Laser Power Variation in a DFB Diode Laser Based Optical Gas Sensor Using a Division Process
Hengtai Chang1, Jun Chang2, Qingjie Huang3
1School of Information Science and Engineering and Shandong Provincial Key Laboratory of Laser Technology and Application, Shandong University, Jinan 250100, China. Hunter_chang@126.com.
Sensors (Basel, Switzerland)
|April 28, 2015
Summary
A novel division process enhances optical gas sensors by eliminating residual amplitude modulation (RAM) in wavelength modulation spectroscopy (WMS). This improves signal quality and ensures stable gas detection despite laser power fluctuations.
Area of Science:
- Optical sensing technologies
- Spectroscopy
- Laser-based gas detection
Background:
- Wavelength modulation spectroscopy (WMS) is susceptible to laser power variations.
- Residual amplitude modulation (RAM) distorts harmonic signals in WMS detection.
- Improving the stability and accuracy of optical gas sensors is crucial for reliable measurements.
Purpose of the Study:
- To investigate a division process for enhancing immunity to laser power variation in DFB diode laser-based optical gas sensors.
- To eliminate RAM in WMS detection through intensity normalization.
- To improve the line shape and stability of detected harmonic signals.
Main Methods:
- Implementation of a division process for intensity normalization.
- Utilizing a DFB diode laser for optical gas sensing.
- Analysis of first harmonic (1f) and second harmonic (2f) signals.
Main Results:
- Significant improvement in signal line shape: Bias reduced from 38.7% to 1.2%, Baseline Difference from 2.7% to 0.69%, and Asymmetry from 15.4% to 0.22% for 1f signals.
- Substantial reduction in Asymmetry Coefficient for 2f signals from 103% to 5.1%.
- Stable detection achieved with low variation coefficients (0.59% for 1f, 0.53% for 2f) over wide dynamic ranges of laser power.
Conclusions:
- The division process effectively eliminates RAM and suppresses laser power influence in WMS.
- The proposed method significantly improves the accuracy and stability of optical gas sensors.
- This technique shows considerable potential for practical applications in gas sensing.
