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Researching Of Methane Optical Fiber Sensing System Based On Wavelength Modulation Spectroscopy

Posted on:2015-09-12Degree:MasterType:Thesis
Country:ChinaCandidate:Y ZhangFull Text:PDF
GTID:2298330452458961Subject:Electromagnetic field and microwave technology
Abstract/Summary:PDF Full Text Request
With the rapid development of society and science technology, more and moregaseous energy is widely used in people’s production and living. Achieving real-timeconcentration monitor for flammable and explosive gas in sensitive areas is veryimportant for protecting people’s life and property effectively. With the rapiddevelopment of distributed feedback (DFB) semiconductor laser and fiber-opticcommunication technology, fiber gas sensing technology based on tunable diode laserspectroscopy (TDLAS) and wavelength modulation spectroscopy (WMS) is graduallyattracting more and more attention of researchers. TDLAS technology is ahigh-sensitive spectrum detection technology, which have a lot of advantages, such ashigh sensitivity, strong anti-noise performance, high precision, fast response, easy toimplement remote measurement and so on. TDLAS technology is now widely used inthe field of gas detection and weak signal detection.Based on the theoretical guidance of WMS, this article carry out a detailedanalysis of harmonic detection theory. According to the ways of formula derivationand software emulation, gas absorption theory and wavelength modulation theorywere researched. The wavelength modulation and gas absorption process of signalwas simulated by system modeling and we acquired the first harmonic signal and thesecond harmonic signal waveform. In hardware implementation, the article elaboratecircuit board design and implementation process of the system, which include thesemiconductor laser diode driving circuit and signal modulation circuit based onoperational amplifier, the sine wave and triangular wave generating circuit, thephotoelectric detection circuit based on MAX4008, the signal frequency multipliercircuit based on AD734, TEC temperature control circuit of semiconductor laserbased on LTC1923, low-pass filter and band-pass filter circuit and lock-in amplifiercircuit based on AD630, etc. At last, the emulation and debugging verification of thesecircuits were carried out.
Keywords/Search Tags:wavelength modulation, weak signal detection, lock-in amplifier, laserdiode driving circuit
PDF Full Text Request
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