双气室气体检测系统的研究

Double gas-cell detection system for gases

基于气体的近红外吸收机理,研究了一种双气室光纤气体检测系统。通过光纤光栅和压电陶瓷对宽带光源LED进行波长调制,获得了与气体吸收峰对应的窄带反射出射光,检测二次谐波,实现气体浓度的较高灵敏度测量。利用测量气室和参考气室的二次谐波的比值来消除吸收系数随环境的变化、光源光功率的波动和光路干扰对测量精度的影响。利用该系统对CH4气体进行了实验研究,实验表明该系统的测量灵敏度可以达到0.2×1-0 6。

An optical fiber gas detection system with two gas cells was developed based on the near infrared absorption mechanism of gases. A Light emitting diode is used as a broadband light source. The wavelength of the LED is modulated by the fiber grating and piezoelectric ceramics to obtain the narrowband reflection output light corresponding to gas absorption peak, and then the high sensitivity detection of gas density can be realized by the detection of the second harmonic. The influence of the beam path interference on the detection accuracy, the variation of absorption coefficient with the environment and the fluctuation of the luminous power were eliminated by the ratio of the two second-harmonic signals from both the measurement and the reference gas cells. The detection experiment for CH4was implemented by the system. Experiment indicates that the measurement sensitivity of the system is 0.2×10^-6.