Research On Optical Fiber Carbon Monoxide Measurement System Based On Infrared Absorption

Carbon monoxide is an important consistent of fossil-fuel power plant's boiler flue gas, realtime and online detection of carbon monoxide has a critical function for boiler's safety operation, fine coal power's optimize burning and environment protection. Firstly, in this paper we used the theory of light interferometry and multi-light interferometry to analyse the working principle of tunable Fabry-Perot cavity, then we discussed spectrum infrared absorption theory of diatomic gas molecule like carbon monoxide. On comparing the character of carbon monoxide's absorption spectrum at near infrared band and middle-infrared and far-infrared bands, and taking account of consistent with low loss window of optic fiber and price etc factors, sinusoidal modulation for Fabry-Perot cavity with oscillating circuit designed is carried out by using the cheap LED operating as light source, by using the frequency-selecting property of tunable Fabry-Perot cavity, carbon monoxide's concentration is detected with harmonic wave. The designs of the light path, circuit and gas cell are based on the theoretic analysis in the paper. For the signals are very weak, the lock-in amplifier is employed to extract the signals in the circuit design. It can inhabit the noise in the most and maximize the signal-to-noise.