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The theoretical and experimental studies of fiber Bragg grating (FBG) sensors is investigated. In the theoretical studies, the coupled-mode theory with transfer matrix method is used to simulate the dynamic responses of the FBG sensors subjected to a sinusoidal strain wave. The numerical results indicate that the increase of frequency and amplitude of strain wave result in signal distortion, hence the signal distortion limit is established to analyze the FBG dynamic sensing range. In the experimental studies, the FBG sensors as well as the strain gage are used to measure simultaneously the transient responses of dynamic strain for a suspended cable under impact loadings. The frequency spectra of the measuring results for transient responses of dynamic strain are analyzed and the natural frequencies of the cable are determined. The natural frequencies obtained from experimental measurements have excellent agreement for different sensors and different impact positions. In addition, the experimental results also have good correspondence with the theoretical analysis and the finite-element method (FEM). According to the available experimental results, it is proved that the FBG sensor has excellent ability of transient strain measurement for structures with curved surface and large curvature and has better performance than the traditional strain gage.
Date of Publication: Dec. 2009