The FDL is composed of a fiber-ring cavity, by which the delay time is matched with the interval length of the adjacent WFBGs. Fibre Bragg grating (FBG) sensors are used to measure various quantities such as temperature, stress, vibrations, pressure, or refractive index. The characteristic feature of these sensors is that the position of the spectrum changes due to the action of a particular physical quantity. Based on the influence of hysteresis and creep of piezoelectric ceramics, a tunable F-P. A demodulation algorithm is vital for a fiber Bragg grating (FBG) sensing system. In this paper, a novel demodulation algorithm based on the variable-step-size method and cross-correlation algorithm is proposed to demodulate the wavelength of an FBG.
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