Research On Single-loop Optical Fiber Sensor For Methane Gas

In recent years, as mining industry, environment monitoring and petrochemical industry being more concerned with methane gas detection, detecting reliably, instantly and rapidly must be the main direction and objection. Optical fiber sensor, due to its electromagnetic immunity, high sensitivity, light weight and easy integration has grasped more attention.Placing gas cell in single-loop optical fiber, an optical fiber sensing system is designed which based on spectrum absorption principle of methane gas. Light pulse generated by DFBLD split up into two parts by coupler, the optical power of one part of which pass through the single-loop optical fiber several times will be attenuated. By fitting the curve of the optical pulse power in the original state and in the gas absorption state, ring-down time is figured out to gain gas absorption loss and gas concentration.On the basis of the principle, a detailed analysis of the fiber ring-down theory is made, by which the gas concentration is figured out, the parts of the system are tested, and structural system is built. Taking account to the system need, driver circuit of DFBLD is designed to achieve the direct current driving, alternating current driving and temperature monitoring, so a reliable light pulse signal are attained. The gas concentration gained by this way is basically coincident with the standards.