Research On The Technique Of The Optical Fiber Bragg Grating Sensors

The project is from the scientific research fund doctor items (20030056017) ofthe ministry of education. The main aim of the research is to have a discussion and abasic study on the sensing field of fiber Bragg grating sensor.Fiber Bragg grating sensor, which is an important branch of fiber sensor, catchesthe attention of us. In the point of view of demodulation, this paper has a research ofthe strain parameter-sensing field of fiber Bragg grating sensor. Also it has designed ademodulation scheme based on unbalance wave-length scanning Michelson fiberinterference technology, upon which the whole system has been set up and debuggedand using this system the strain characteristics experiment of fiber Bragg grating wascompleted.1. According to the theory of coupling, the light-wave travel law in the fiberBragg grating has been studied, the even cycle transmission response character offiber Bragg grating was deduced, a numeral simulation of the reflection spectrum offiber Bragg grating was made, and the relationship between the refractive indexmodulation depth δ neff, length L and the characteristics of fiber Bragg grating hasbeen analyzed. Also the strain and temperature sensing models of fiber Bragg gratingwas studied and through the analyze of fiber's spring effect, cycle flex, calorescenceeffect and the heat expand effect, the strain sensitivity, temperature sensitivity and thepressure sensitivity of fiber Bragg grating were gained.2. The demodulation theory of fiber Bragg grating has been systemically studiedand a model based upon the Michelson fiber interference theory has been set up. Inthis paper, the whole system has been analyzed in every detail and particular, and theselective foundation and designing idea of every equipment has been introduced.3. The design and modulation of fiber Bragg grating demodulation signalprocessing system have been finished, the conversion between light and electricity,the filter wave of noise and RS discrimination has been realized, and the phasemeasuring system cored on 89C51 single chip computer has been designed, which candisplay the cycle wave signal and phase pulse width signal at any time, whoseresolution reaches 0 .036°.4. The fiber Bragg grating demodulation system based on Michelson interferencedemodulation theory has been set up. Using this system, the strain effect of fiberBragg grating has been studied and the standard deviation is σ =0.01782nm.Through the adjustment of the data, the actual modulation sensitivity was got, whichis 0. 1573nm/mm, and the strain sensitivity is 1 .294pm /με.