全光式石英增强光声光谱系统光纤法珀解调技术研究

Research on the Fiber Fabry-Perot Demodulation Technique Based on All-Optical Quartz Enhanced Photoacoustic Spectroscopy System

基于光纤法珀工作点稳定技术提出了一种适用于全光式石英增强型光声光谱(QEPAS)探测技术的光纤法珀解调系统。利用可调谐光纤激光器作为探测光源,采用法珀干涉光强的直流信号作为误差反馈信号,将工作点锁定在正交相位点上,提高光纤法珀系统的稳定性,从而提高了光声信号探测的准确性。将其应用于全光式石英增强型光声光谱气体探测系统,并在开放环境中完成了对水蒸气的探测实验,得到其归一化噪声等效吸收系数为1.81×10-7W(cm·Hz)。实验结果表明,相比于一般的全光式石英增强型光声光谱系统,该方法的探测灵敏度提高了1.2倍。

In all-optical quartz-enhanced photoacoustic spectroscopy （QEPAS） system, a Fabry-Perot demodulation method based on operating point stabilization technology is proposed. For improving the detection accuracy of the photoacoustic signal, a tunable erbium-doped fiber ring laser is used as the detection light source and a detection technique based on the direct-current error signal is employed to lock the operating point to the quadrature phase point in the system. The experiment for detection of water vapour in the open environment is carried out and a normalized noise equivalent absorption coefficient of 1.81× 10-7 W/（cm. √Hz） is achieved, which is about 1.2 times higher than that of conventional QEPAS.