We describe the characterization of the temperature and strain responses of fiber Bragg grating sensors by use of an interferometric interrogation technique to provide an absolute measurement of the grating wavelength. The fiber Bragg grating temperature response was found to be nonlinear over the temperature range Ϫ70°C to 80°C. The nonlinearity was observed to be a quadratic function of temperature, arising from the linear dependence on temperature of the thermo-optic coefficient of silica glass over this range, and is in good agreement with a theoretical model.
We present the implementation of optical load sensors utilizing mechanically induced reversible sampled fiber Bragg gratings (SFBGs). The load is measured by the reflectivity of the first-order Fourier component of the induced SFBGs. The theoretical and experimental characterization indicates that such SFBGs can be tailored to realize load sensors with high sensitivity of near-linear response and free of influence from environmental and system noises.
This paper shows that two annealing processes must be considered when predicting the effect of temperature on fibre Bragg gratings that have been written by UV radiation in boron/germania co-doped fibres. Both the thermal decay of the grating-related refractive index and the annealing of the boron-induced refractive index contribute to the wavelength shift observed. We have combined the theory of these two effects to match data taken experimentally (accuracy ±0.3 nm) and successfully explained a selection of observed wavelength shifts ranging from −2.83 to +0.75 nm.
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