基于频移干涉光纤腔衰荡技术的甲烷传感系统

Methane Sensing System Based on Frequency-Shifted Interferometry Fiber Cavity Ring-Down Technology

煤矿事故严重威胁人们的生命和财产安全,瓦斯作为煤矿事故的罪魁祸首,其主要成分是甲烷。因此,选择一种性能优良并且能够实时探测甲烷浓度的气体传感器对安全生产和检测大气环境是十分有意义的。在众多气体传感器中,光纤气体传感器由于容量大、损耗小、体积小、抗腐蚀、抗干扰能力强等优势受到学者和仪器制造商的青睐。本文对比了几种光纤气体传感器,基于光谱吸收技术的光纤气体传感器体积小、成本低、功耗小,其使用最为广泛。在光谱吸收技术的基础上,发展了一种高灵敏度的探测技术,腔衰荡CRD(Cavity Ring-Down)技术。相比于普通的光谱吸收技术,其吸收光程长,灵敏度高出3个～4个数量级,并且对光源强度稳定性要求不高。但是,为了有效、实时地探测到衰荡信号,该技术对探测器的速度要求极高。本文研究的频移干涉腔衰荡FSI-CRD(Frequency-Shifted Interferometry Cavity Ring-Down)技术,通过将腔衰荡技术结合频移干涉技术,构建了频移干涉腔衰荡甲烷传感系统,实现了衰荡信号从时间域到频域的转换,降低了对探测设备的要求,并通过实验验证了该系统可以用于甲烷气体浓度的测量。

Coal mine accidents seriously threaten people's lives and property safety,and gas is the main culprit of coal mine accidents.Its main component is methane.Therefore,choosing a gas sensor with excellent performance and real-time detection of methane concentration is very meaningful for safe production and detection of atmospheric environment.Among many gas sensors,optical fiber gas sensors are favored by scholars and instrument manufacturers because of their advantages of large capacity,low loss,small size,corrosion resistance,and strong anti-interference ability.This article compares several kinds of optical fiber gas sensors.Optical fiber gas sensors based on spectral absorption technology are small in size,low in cost,and low in power consumption,and are most widely used.Based on the spectral absorption technology,a high-sensitivity detection technology,cavity ring-down technology has been developed.Compared with the common spectral absorption technology,the absorption path length is long,the sensitivity is 3~4 orders of magnitude higher,and the requirement for the strength of the light source is not high.However,in order to detect the ringing signal in an efficient and real-time manner,this technique requires a very high speed of the detector.In this paper,the frequency shift interferometric ring-down technique is studied.By combining the cavity ringing technique with the frequency shift interference technique,a frequency-shifting interferometric ring-down ringing methane sensing system is constructed,and the ring-down signal is converted from the time domain to the frequency domain.The requirements for detection equipment have been reduced,and experiments have verified that the system can be used for the measurement of methane gas concentration.