Optical fibers can be used as a promising sensors in smart structures thanks to their novel characteristics. In particular,
its immunity to electromagnetic interference (EMI) makes the sensor suitable for use in electronic environments. In
order to inspect the reliability of a structure, it is essential to characterize the dynamic responses of the structure. An
accelerometer associated with optical fiber makes it possible to conduct real-time structural health monitoring under high
electromagnetic environments. This paper describes an optimal design of a novel fiber optic accelerometer using one
grating panel for the application to civil engineering structures. The fiber optic sensor design was optimized to have the
best sensitivity to the motion of the reflective grating using two optical fibers in the quadrature. The reflected optical
signal of the sensor is influenced by the reflective grating pattern and optical fiber-grating distance. In this paper, several
simulations and experiments were carried out to evaluate the characteristics of the output signals according to the grating
pattern and the distance between the optical fiber and the grating for a fixed fiber core diameter. Through comparison of
the results between the simulations and the experiments, the optimum design of the grating-pattern was determined to
obtain a stable and periodic sine wave as the output signal. Furthermore, it was demonstrated that the output signals
reflected by one grating panel could be used for the final parameter-measurement.
The reflective spectrum of fiber Bragg grating (FBG) sensor under axial uniform stresses has a single peak with
narrow bandwidth and high reflectivity. But, if the impact-induced damage is generated around FBG sensor attached on
the sandwich panel, peak splits can occur due to strain gradient and transverse loading. The detection of the impact-induced
damage is very important for structural safety, because this damage can degrade the flexural properties of
sandwich panels. From the experiments, the impact-induced damages were detected by using the reflective spectrum
change of FBG sensors. Bending stiffness, among the key flexural properties of sandwich panels were measured by 4-point bending test. By matching these results at each experiment, the flexural property degradation of sandwich panels
can be estimated after impacts at different energy levels. The survivability of FBG sensors after impact was found to be
acceptable, as 11 out of 17 FBG sensors remained intact after the impact test.
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