| With the modernization of industry and the improvement of people's life, the consumption of fossil fuel, such as petroleum, natural gas and coal, is being increased fast. Because of the equipment and combustion methods, more and more baneful gases are released into the air, which are harmful to people's health and life. Based on this fact, researching and fabricating a kind of new gas sensor with high sensitivity and real-time detection has an important theoretic and realistic significance.After comparing main advantage and disadvantage of all theories of gas concentration measurement, SO2 is choosed as the object to research a kind of SO2 concentration measurement apparatus on the base of theories of spectrum absorption and harmonic detection. The development of optical fiber gas sensor was thoroughly reviewed in this paper, from which some drawbacks and application limitations of ongoing optical fiber gas sensing techniques were extracted. The molecule's structure, the molecule's spectrum and infrared spectrum structure of SO2 are introduced. Optical fiber sensing theory and harmonic detection technology are introduced in this paper.Harmonic detection technique of gas concentration sensing based on infrared absorption phenomena of gases is presented. This is a novel optical fiber sulfur dioxide sensor. This method offers high selectivity, long life time, no influence of surroundings gases, no electrical induction and so on. It adapts to be used in the foul and hazardous environment. The hardware of this apparatus is designed, such as light path design, gas chamber fabricating and light source drive. The most important is to optimize the design of light path and electronic circuit of the system so as to maximize the SNR through noise inhibition.At the end of paper, the experiments are carried through including the experiment of the waste of light route and the result of the fiber sensing detection. The system of fiber gas sensing is proved by experiment. |
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