Research On Optical Fiber Methane Gas Sensor

Methane is the main component of methane gas, and coal mine methane gas explosion accidents not only bring serious economic loss, but also cause huge casualities. Therefore, an accurate real-time dynamic monitoring of coal mine with methane gas is very important. Under the current mine, the existence of traditonal monitoring methods are unsafe, imconvenient and have other shortcomings, howrere the method based on the principle of optical absorption spectra of methane gas sensor has so many advantages such as high safety, litter affected by environmental factors, suitable for remote messurement and high accuracy, easy-to-network, and so on, and the method will attracts more and more attention.This thesis analyzed the principle of infrared absorpton of methane gas, and studied the absorpton spectrum of methane and absorption coefficient. In contrast to the characteristics of several solutions, wo proposed a difference method to detect the methane concentration, and improved it with comb filter. We simulated the experimental results and obtained the corresponding curve diagram.We use a SLED broadband light source. In the optical part, a broad filter filters out the band we need; gas cell is used to let gas pass in and get out; the sensing unit uses a cascade collimator and a several feflective part as the optical sensing probe, and the latter one is more practical, so we use it; a light demultiplexer is designed to separate the signal light and the reference light.Finally we described the principles and performances of the light source and detector in detail, and described the basic principles of analog-digital conversion.We have done an experiment under this system, the analysis of data results show that the program is feasible and can satisfy the low concentration measurement requirement, but there is error too, and we also have done analyzed with it. The system needs further improvement and testing. In theory, the system has a detecting accuracy with 410ppm.