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Researches On LPFG Fabricated And The Refractive Index Sensing Of Application

Posted on:2017-05-06Degree:MasterType:Thesis
Country:ChinaCandidate:Y N YangFull Text:PDF
GTID:2308330503982396Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Various kinds of sensors based on fiber grating have the advantages of high precision, corrosion resistance, electromagnetic interference, and have potential application prospects in civil and military fields. At present, the factors restrict the further development of grating sensors mainly concentrated in the writing technique is still in low level, the characteristic of the grating can’t meet the needs of various types sensors. Recently, the widely applied UV exposure method utilizing phase mask has achieved the industrial mass production, but there are some disadvantages, the writing technique is so complex and the cost is expensive. The fabrication technique of LPFG using CO2-laser output laser power with simple writing technique, high efficient and low in cost. Our research group has studied the theoretical foundations of CO2-laser outout power writing technique, but the LPFG is extremely fragile, high insertion loss and los of sidelobes in grating, so it’s difficult to research sensors. This paper research that how to increase the technique of writing grating using CO2-laser output laser power and use it for refractive index. The specific research work of this paper is summarized as follows:Firstly, the fabrication technology of the long-period fiber grating is introduced and the applications in sensing areas are also stated. Research the formation mechanism of different methods writing technique and analysis the coupled-mode theory whta is manufacturing thchnology of fiber grating.Secondly, the platform system of CO2-laser writing technology is established, and the factors that affect the characteristics of the grating are analyzed, and the corresponding measures are put forward. CO2-laser with low power exposure can vary the coupling characteristics of the annealed LPFG in hydrogen loaded fiber, low insertion loss, more coupled model, narrow bandwidth and so on. And a small cycle LPFG is engraved by CO2-laser.Thirdly, analysis the theory of refractive index sensing, then using the grating that written by different methods for refractive index experiment. The sensitivity and the linear change of the experimental parameters are compared.Finally, there are many defects demodulate the information by spectrograph, and the LPFG+FBG demodulation system is designed that the sensitivity is increased.
Keywords/Search Tags:LPFG, CO2-laser out put low power writing LPFG, hydrogen loaded fiber, short-period LPFG, refractive index sensing
PDF Full Text Request
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