Applied Research On Optical Fiber Sensing In Gas Examination

Along with the coal industry development, the gas accident more and more becomes to an important factor restricting the coal mine safety. The gas sensor plays very important role of monitoring, therefore it is significant to develop safe reliable, the high sensitivity gas sensing system. It has the great society and the economical significance. The optical fiber gas sensor has found a wide range of applicants by virtue of its various technical merits. The goal of the paper lies in designing the optical fiber methane gas sensing system to examine gas density real-time and reliably.After analyzing the theory of near-infrared selective absorption of gas, we describe the academic base of the measurement of the gas by absorption theory. The absorption spectra of methane are confirmed and the spectrum characteristic, which is fit for low-loss optical fiber to transmit a long way, is also discussed.When the gas is examined directly according to Lambert-beer law, there is not only light route interference, but also no relationship between content and density. Then the signal is very difficult to amplify, and measurement sensitivity is strictly limited. Difference absorption measurement and wavelength modulation harmonic measurement are two fundamental approaches for gas light absorption detection. For different light resource, system designs have great differences. This paper gives several design plans.As a result of experimental condition limit, this paper adopts SLD light source forming ordinary light emitting diode to get narrow band light source through wavelength modulation by Bragg grating and piezoelectric ceramic. It realizes high sensitivity examination of gas density. The software of system adopts LabVIEW software to gather and analyze the data. That simplifies the design by software instead of hardware. The gas density can be displayed in user-friendly interface and saved.