标题：Gas Absorption Center-Based Wavelength Calibration Technique in QEPAS System for SNR Improvement
作者：Wang, Zongliang; Chang, Jun; Liu, Qi; Tian, Cunwei; Zhang, Qinduan
作者机构：[Wang, Zongliang; Liu, Qi; Tian, Cunwei] Liaocheng Univ, Sch Phys Sci & Informat Technol, Liaocheng 252000, Peoples R China.; [Wang, Zongliang; Liu, 更多
通讯作者：Wang, ZL;Wang, ZL;Wang, Zongliang
通讯作者地址：[Wang, ZL]Liaocheng Univ, Sch Phys Sci & Informat Technol, Liaocheng 252000, Peoples R China;[Wang, ZL]Liaocheng Univ, Shandong Key Lab Opt Commun Sci 更多
关键词：QEPAS; DFB-LD; wavelength calibration; fiber gas sensor
摘要：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.