Research On Multi-Type Gas Concentration Measurement Based On Fiber-Circled Cavity Ring-Down Method

The poisonous, harmful, combustible and explosive gases exhausted by the industrial production seriously pollute the environment and threat human health and industrial production. Therefore, it is very important to detect their concentrations. For years, many gas concentration measurement methods have been proposed, which complete the gas concentration detection mission in different degree. But until now, a satisfactory high accuracy gas concentration in-situ measurement method in special situation hasn't turn up. In this paper, researches on high accuracy gas concentration in-situ measurement in special situation are studied. The primary content includes:First, the measurement principle of the multi-type gas concentration is analyzed, and the factors that effect the gas concentration measurement precision, sensitivity and resolution are researched.Second, the structure of the multi-type gas concentration in-situ measurement system is presented, and the performance and working principle of each device are analyzed. A new type variable erbium doped fiber amplifier and a new type variable optical attenuator are designed, then the attenuation characteristics of the variable optical attenuator are theoretically emulated.Last, the multi-type gas concentration in-situ measurement system based on fiber-circled cavity ring-down method is designed. The gain characteristics of the designed variable erbium doped fiber amplifier are analyzed. The manufacturing process of the designed variable optical attenuator is given and the variable optical attenuator attenuation characteristics are proved by the experiment. Then, the experimental analysis of the gas concentration in-situ measurement that uses the designed system is performed, and the gas-to-light absorption characteristics in the same gas but different concentrations with time changing are given, then, the ring-down time-absorption coefficient-gas concentration relation is analyzed. The effects are quite satisfactory.