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.
It is widely known that materials exposed to the severe low earth orbit (LEO) environment undergo degradations. For the
evaluation of fiber Bragg grating (FBG) sensors in the LEO environment, the reflective spectrum change and the Bragg
wavelength shift of FBG sensor were measured during aging cycles simulating the LEO environment. The LEO
environment was simulated by high vacuum (~10-5 Torr), ultraviolet (UV) radiation (<200nm wavelength), temperature
cycling (-30°C~100°C), and atomic oxygen atmosphere (AO flux of 9.12×1014 atoms/cm2/s and kinetic energy of ~0.04
eV). FBG sensor arrays were embedded into the graphite/epoxy composite material. Through the aging cycles simulated
for the LEO environment, the change in the reflective spectrums and the Bragg wavelengths from FBG sensors were
investigated.
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