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Study On Fibre Bragg Grating Sensing Characteristics And Multipoint Multiplexing Technology

Posted on:2013-07-04Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y B DaiFull Text:PDF
GTID:1268330392967566Subject:Instrument Science and Technology
Abstract/Summary:PDF Full Text Request
In recent years, Fibre Bragg grating sensor technology has become a newdevelopment orientation in the sensoring field. It has some performances such aslight weight, electromagnetic immunity, corrosion resistant, easy to access into fiberoptic sensor networks etc., It’s widely used in aerospace, oil and electric power, civilengineering, biochemistry and medicine. In this paper, firstly, based on the theory offiber Bragg grating, a time-division multiplexed (TDM) model of fiber Bragg gratinghas been built up. Secondly, followed on the basis of a variety of fiber Bragg gratingmultiplexing technology, a large capacity multiplexing scheme of fiber Bragg gratingis put forward, it’s principle is analyzed and its performance is verified byexperiments. The main works are as follows:1. Based on Fibre Bragg grating coupled theory, calculation methods and spectralcharacteristics of fibre Bragg grating is studied, and the relationship betweenreflectivity and refractive index modulation depth, length of grating is obtained.A time division multiplexing model is established, and the relationship betweenthe reflectivity and the number of sensors is studied. The crosstalk caused byspectral shadow and multiple reflection effect between the FBGs is analyzed.2. Based on the TDM model, the author proposes a time-division multiplexingscheme using SOA resonant cavity, in which each of sensor is addressed byusing pulse singal with different frequency. The relationship between crosstalkof sensor and width of pulse, and the relationship between attenuation of cavityand the capacity of sensor are also studied, respectively. Combined the SOAresonant cavity technology, a large capacity multiplexing technology with mixedtime-division and wave-division multiplexing (TDM+WDM) is proposed. It’ssensor array consists of different groups and each group comprises of fewsensors, the group is addressed by TDM mode and each sensor is accessed byWDM mode, the total multiplexing capacity is multiplication of TDM andWDM.3. Sensing characteristics and packaging technology of FBG is studied accordingto the performance of corss sensitivity characteristics to temperature and strain,a temperature, strain, pressure sensors is developed respectively, and theircoefficients are calibrated.4. A time-division multiplexing sensing system is developed based on SOAresonant cavity. Experimental setups of TDM sensor system are built up.Temperatures and strains are monitored by using the TDM methord with5 temperature sensors and4strain sensors in a monofilament fiber. The multi-point multiplexing capability of TDM system is verifed by monitoring eachsensing point. A two dimensional FBG sensing network with5×5sensors arrayis set up based on TDM+WDM technology. The stress/temperature distributionin a aluminum plate is measured under different loading/heating by using thisFBG sensing network.
Keywords/Search Tags:fibre Bragg grating, semiconductor optical amplifier, wavelengthdivision multiplexing, time division multiplexing
PDF Full Text Request
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