Research On Demodulation Of Fiber Bragg Grating Sensors

Fiber grating Sensors are new type of passive optical components, which can be used to measure lots of physical parameters. With the photosensitivity of fiber, they get the periodical distribution of refraction index in fiber core. Fiber gratings have several distinguished advantages over normal fibers. With the fast development, fiber grating sensors make lots of multiplex nerve sensing networks become possible, which can be adopted in the situation that normal sensors would be in trouble.As a new type of sensing technology, the fiber grating sensing technology has been caused extensively focus. At present, fiber grating sensors have been reported to measure lots of physical parameters, such as temperature, strain, pressure, displacement, intensity of pressure, tweak angle, acceleration etc, some of them have been in practical application.Based on analyzing and studying principle of demodulation technique for FBG, a demodulation scheme of Fiber Bragg grating sensors was designed, and experiments were carried out. The main works are as follows:(1) The basic theory of analyzing FBG was introduced, including Coupled Mode theory, Transfer Matrix method, and Fourier Transform method.(2) The FBG sensing mechanism was investigated. Its characteristics of temperature and strain were tested, and the research results show that the temperature and strain vary linearly with the shift of wavelength.(3) Fiber Bragg grating sensor signal demodulation scheme was investigated. A new temperature-nonsensitive demodulation scheme based on double triangle cantilever was proposed. The experimental results verified its effectivity.(4) A demodulation scheme of Fiber Bragg grating sensors which is based on M-Z interferometer was designed. The relation between temperature and the change of the output optical power was gained through theoretical analysis.(5) Based on the demodulation scheme designed, the temperature and optical power response of FBG were experimentally tested. The feasibility of this demodulation scheme was confirmed.