查看更多>>摘要：Slope-assisted Brillouin optical correlation-domain reflectometry (SA-BOCDR) is a recently developed structural health monitoring technique for measuring strain and temperature distributions along optical fibers. Although its fundamental operations have been demonstrated with some unique features, no measurement using optical fibers embedded in actual structures has been reported yet. In this work, as a first step to such practical applications, we present an example of SA-BOCDR-based structural diagnosis using composite structure comprising carbon fiber reinforced plastics. The system output well agrees the actual strain distributions. We also detect the breakage of the embedded fiber, showing the potential usefulness of SA-BOCDR in practical fields.
查看更多>>摘要：We measure the strain dependence of multiple Bragg wavelengths (corresponding to different diffraction orders) of a fiber Bragg grating (FBG) inscribed in a perfluorinated graded-index plastic optical fiber (PFGI-POF) in the wavelength range up to 1550 nm. Based on this result, we show that the fractional sensitivity, which has been conventionally used as a wavelength-independent index for fair comparison of the FBG performance measured at different wavelengths, is dependent on wavelength in this range. The reason of this behavior seems to originate from the non-negligible wavelength dependence of refractive index and its strain-dependence coefficient. Using the wavelength dependence of the refractive index already reported for bulk, we deduce the wavelength dependence of the strain coefficient of the refractive index. This information will be a useful archive in implementing PFGI-POF-based strain sensors based not only on FBGs but also on Brillouin scattering in future.
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