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Study On New Techniques Of Extrinsic Fabry-Perot Interferometric Sensors

Posted on:2005-02-03Degree:MasterType:Thesis
Country:ChinaCandidate:J JiangFull Text:PDF
GTID:2168360125963938Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
With the development of modern measurement technology, more and more research interests are focused to optical fiber sensors in the past two decades. Compared to conventional electrical sensors, optical fiber sensors offer several outstanding advantages, including immunity to electromagnetic interference, capability of responding to a wide variety of measurands, high resolution, capability of multiplexing, small size and light weight, and resistance to harsh environments. Extrinsic optical fiber Fabry-Perot interferometric sensors (EFPI) is one of the most successful optical fiber sensors in practice. After described the research history and current status of EFPI, it can be seen that optical fiber EFPI sensors exist some limitations, such as, one sensor can only measure one parameter, signal is week, and sensors are hardly multiplexed, etc. Hence, we would find some ways to overcome these limitations.The main work completed is summarized as follows: I. Several ways of demodulating the signal from EFPI sensors: intensity-, phase- and frequency-domain-demodulation are analyzed. In addition, their disadvantages and advantages are also discussed, respectively. II. The temperature characteristics of the resonance wavelength and resonance peak value for the long period fiber grating (LPFG) written by the high frequency CO2 laser pulse is analyzed. Several experiments are carried out to verify that such a LPFG has the good temperature characteristics. On the other hand, it can be used in environment with high temperature which is not possible for the LPFG written by ultraviolet light. It is the first time to integrate the LPFG and EFPI in a quartz tube to make a compact sensor which can measure temperature and strain simultaneously. The experimental results prove that this kind of integrated sensor can achieve a temperature accuracy of ±0.5℃ and a strain accuracy of ±20??. III. The power transmission equation and the basic principle of Erbium-doped fiber (EDF) amplification system is analyzed. It is also the first time that put forward a new method to improve the intensity of EFPI sensor signal. An EFPI sensing system based on optical amplification which can improve the intensity by 104 is designed. A relatively high SNR is achieved while the system cost is not increased. IV. It is still the first time to bring forward a new method of spatial-frequency-multiplexing the optical fiber Fizeau sensors which are designed on the basis of EFPI sensors. Compared with the multiplexing method used in the former time, this method has some advantages, such as simple structure and a great potential. A new method which can multiplex more than ten optical fiber Fizeau strain sensors in the spatial-frequency-domain is put forward. The frequency-domain-demodulation and polynomial value-inserted arithmetic are used to achieve high accuracy and resolution. The experimental results show that this kind of multiplexed sensors system can achieve the strain measuring accuracy of ±20?? with the resolution of 1??.
Keywords/Search Tags:Optical fiber Fabry-Perot interferometric sensors, Long period fiber gratings, Erbium-doped fiber, Optical fiber Fizeau sensors, Multiplex, Temperature, Strain
PDF Full Text Request
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