Distributed Strain Sensing from Damaged Composite Materials Based on Shape Variation of the Brillouin Spectrum

Abstract

Among fiber-optic distributed sensors, Brillouin optical time domain reflectometry (BOTDR) can effectively measure overall strain in a structure. However, since the spatial resolution of BOTDR is generally more than 1 m, it is difficult to detect inhomogeneous strain distributed within 1 m along a fiber. In this paper, we propose a new technique to detect strain changing sharply within the length of the spatial resolution. This technique is based on the fact that the profile of the Brillouin spectrum changes depending on strain distributions. We confirmed the dependency of the Brillouin spectrum on strain distributions theoretically and experimentally.