Study On The Fiber Sensor For Coal Mine Gas Detection

Optical fiber sensing is a new technology; it has wide applications in many areas. Optical fiber sensor has lots of advantages, for example, high sensibility, anti-electromagnetic interference, anti-erosion, easiness to form a network, simplicity, etc. It attracts the interests of many research groups all over the world. One of the most important applications is the methane detection in coal mine.This thesis gives the method of methane sensing based on the optical spectrum absorption by taking into account of the narrow bandwidth filtering of the Fiber Bragg Grating (FBG) and the low transmission loss of the optical fiber. The main points of this thesis are described as follows:The optical absorption spectra of some gases are studied, and the methane absorption spectrum is measured.The key characteristics of the sensor are studied and researched deeply. The sensor is designed; the stability and the reliability are studied. The sensor has lots of advantages such as small scale, low loss, long working distance etc. In order to keep clean of the sensor unit, we design a gas cell for the sensor, which can keep the dust in the coal mine out of the cell. Detection and treatment of the signal is one of the key difficulties in this system. In order to enhance the stability and the sensibility of the sensor, the amplification and the circuit are improved, the algorithm in data acquisition and programming are also studied in the meantime.Experiments are carried out based on the preparations described above. The experimental results and the remained questions are analyzed. It shows a good performance either in the friendly interface or the sound and light alarming parts. The sensibility reaches 0.1% methane concentration. It is sufficient to be used in the methane monitoring of the coal mine.