Erbium-Doped Fiber Laser For Applications Of Acetylene Gas Detection

Acetylene is a very active chemical properties of gas, burns easily, decomposition and explosion, the explosion of acetylene in the air range of 2.5% to 80%, as compared with other flammable gases, acetylene have low explosion lower, and the acetylene is a transformer fault gas. So it is very important to detecting acetylene concentration in factories safety and environment inspecting areas. Acetylene concentration measurement is the paper's purpose. Fiber acetylene gas sensing technique is studied based on the principle of spectrum absorption.Firstly, basic Laser theory and the structures and the sorts of laser are presented briefly, Based on three-level system model, analytic expressions to output power, threshold pump power and slope efficiency of linear EDFL are found. A simple solution to ASE power in laser band is given. Working principle of fiber Bragg grating are analyzed, such components is tunable erbium-doped fiber laser necessary.Secondly, the characteristics and influences on measurement of light source, gas cell, optical path are analyzed. The relations of output power, threshold pump power, slope efficiency and ASE power in laser band with different pump power and Bragg grating reflectivity are discussed using numeric imitation with MATLAB. The grin lens gas cell is designed which can reduce interference signal. And the principle of intra-cavity absorption spectroscopy technique is given. Therefore, the high sensitivity can reached in detect gas concentration.Finally, to compensate for the acetylene weak absorption in near-infrared region, extension of effective absorber length detection techniques are employed. Based on the current experimental device, the characteristics of the source spectrum and the near-infrared absorption of acetylene are tested. The acetylene concentration detection, the repeatability and stability of the system are studied. The experiments results have proved that the system is feasible.