| In resent years, accidents in coalmine happened frequently in our country, the situation of safety production for coal mine is rather critical. Gas sensor plays an important role in monitor system, and then the development of a high sensitive gas sensor system with great safety and dependability has great social and economical significance. Optical fiber gas sensor has found a wide range of applications by virtue of its various technical merits. Feedback laser which generates narrow band light source for the Optical fiber gas sensor is too expensive to be used in engineering. According to this question, this paper adopts wide band light source form ordinary light emitting diode to get narrow band light source through wavelength modulation by Bragg grating and piezoelectric ceramic. To increase the sensitivity of the optical fiber gas sensor, neural network method is used to adjust the voltage of the piezoelectric ceramic. While modulating the light source, the transmitted signal is used to calculate the reflected second harmonic signal, which is in proportion to the gas concentration. In this way the instability of the light source is eliminated in principle. In the end, a data acquisition and analysis system based on the virtual instrument technique was designed. With the powerful digital processing ability of the computer, the signal will be analyzed and displayed in user-friendly interface, and the saved history data can also be used in other related work. |
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