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Research On Sensing Characteristics And Measurements Based On Long-period Fiber Gratings

Posted on:2016-06-08Degree:MasterType:Thesis
Country:ChinaCandidate:M J ChenFull Text:PDF
GTID:2308330464453765Subject:Electronic Science and Technology
Abstract/Summary:PDF Full Text Request
Fiber grating is one of the most important devices in domain of optical communication,sensing and optical information processing.Long-period fiber grating(LPFG) sensor is developed quickly in recent years.The principle of transmitting light based on LPFG is that forward transmitting mode of core couples to forward transmitting modes of cladding.So LPFG has no backward transmitting light and it need not fix the isolator between LPFG and light source.The resonant wavelengths and the values of wastage are more sensitive to changes of environment because of this characteristics.Therefor it has higher sensitivity on temperature,bend,distortion,transverse load,concentration,refractive index than that of Bragg fiber gratings.Furthermore LPFG sensor is characterized by its high flexibility,wide? range of measure,not disturbed by electromagnetism,not easy to be rotten,being light in weight and small in bulk.So LPFG is widely used for measure in industry and agriculture real time and on-line.The working mechanism determines LPFG’s feature and application.This paper attempts a series of studies on the working mechanism and the sensor application of LPFG in four parts as following:1. Introduce the development and sort of the fiber grating and the trend of sensors.2.Analyze the producing methods of LPFG and its application in communication and sensors realm.3.Analyze the characteristics of LPFG and draw some useful conclusions as following:(1)The wavelength increase with the mounting modulation of refractive index.(2)The effective refractive index of core minish along with the wavelength increase;it will increase when the radius of core increase.(3)The effective refractive of high cladding modes increase with the increase of cladding radius and the effective refractive of low cladding modes haven’t changed with small cladding radius.(4)The core coupling coefficients diminish with the increase of wavelength,yet the cladding coupling coefficients are complex.4.Study the LPFG sensors characteristics of the temperature,the axial strain and the refractive index in detail. Based on the study,we put forward and analyze a high-sensitivity cascaded long period fiber grating temperature and strain sensor.In addition,two methods for simultaneous measurement of liquid temperature and refractive index are proposed by a long-period grating.
Keywords/Search Tags:long-period fiber grating, transmission spectrum, resonant wavelength, temperature sensor, strain sensor, refractive sensor
PDF Full Text Request
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