Photonic Sensors, 2018, 8 (4): 04358, 网络出版: 2018-10-07
Gas Absorption Center-Based Wavelength Calibration Technique in QEPAS System for SNR Improvement
Gas Absorption Center-Based Wavelength Calibration Technique in QEPAS System for SNR Improvement
摘要
Abstract
A simple and effective wavelength calibration scheme is proposed in a quartz enhanced photoacoustic spectroscopy (QEPAS) system for trace gas detection. A reference gas cell is connected an InGaAs photodetector for detecting the absorption intensity peak caused by the gas to calibrate the gas absorption center using distributed feedback laser diode (DFB-LD) with sawtooth wave driver current. The gas absorption wavelength calibration and gas sensing operations are conducted at a special internal to eliminate the wavelength shift of DFB-LD caused by the ambient fluctuations. Compared with the conventional wavelength modulation spectroscopy (WMS), this method uses a lower lock-in amplifier bandwidth and averaging algorithm to improve signal noise ratio (SNR). Water vapor is chosen as a sample gas to evaluate its performance. In the experiments, the impact of sawtooth wave frequency and lock-in amplifier bandwidth on the harmonic signal is analyzed, and the wavelength-calibration technique-based system achieves a minimum detection limit (MDL) of 790 ppbv and SNR with 13.4 improvement factor compared with the conventional WMS system.
, , , , . Gas Absorption Center-Based Wavelength Calibration Technique in QEPAS System for SNR Improvement[J]. Photonic Sensors, 2018, 8(4): 04358. Zongliang WANG, Jun CHANG, Qi LIU, Cunwei TIAN, Qinduan ZHANG. Gas Absorption Center-Based Wavelength Calibration Technique in QEPAS System for SNR Improvement[J]. Photonic Sensors, 2018, 8(4): 04358.