Gas Absorption Center-Based Wavelength Calibration Technique in QEPAS System for SNR Improvement

• 来源期刊: 光子传感器（英文版）
• 关键词: QEPAS DFB-LD wavelength calibration fiber gas sensor
• 年，卷（期）: 2018,（4）
• 页码范围: 358-366
• 页数: 9页
• 语种: 英文
• DOI: 10.1007/s13320-018-0502-0

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 790ppbv and SNR with 13.4 improvement factor compared with the conventional WMS system.