Fiber Methane Gas Sensor System And The Light Source Driver

In recent years, the coal-mine accident happens so frequently, that it causes great repercussions in society. On the issue of coal-mine accident, the first casualty is the gas explosion, thus establishing the online and real-time gas monitoring system is very necessary. Fiber-optical sensor has the features of high sensitivity, rapid reaction, easy-to-network and so on. Besides, the security and non-pollution of the optical signal makes the fiber-optical sensor have a rapid development in detecting flammable and explosive gas. This thesis will introduce a system of fiber-optical methane sensor.This system is a methane concentration detection system that bases on the principle of gas spectral absorption. The light from the SLED passes a wide-band filter, and then it is filtered by two comb-filter, one is the detection light and the other is the reference light. The two light is detected by PIN, then the signals war processed by the MCU to collect the information of the methane concentration. The thesis analyzes the parameters of the parts, which compose the whole system.The stability of the SLED is very important to the system. In this thesis it also gives the design of the driver of the light source. The driver is composed by constant-current source and temperature controller. The constant-current source can export 0-1A current under the dictate of MCU, and the temperature controller can make the source work in the stable temperature. Also there are some protection circuits to promise the safety of the source, and the TEC is controlled by the PID circuit to promise the stability of the temperature.At the end of the thesis, gives some test data of the system and the processing method of the data.