Structural monitoring of a bending beam using Brillouin distributed optical fiber sensors

Due to the large measurement range, distributed optical fiber sensors are very effective in the monitoring of large structures. Brillouin distributed optical fiber sensors, which measure strain by using Brillouin frequency shift, show some measurement error for non-uniformily distributed strain because of their spatial resolution characteristics. They require compensation of measured values and positions in the end-parts of the measurement range because measured values are not distributed over all the positions of the spatial resolution range. In this paper, we present the strain measurement characteristics of Brillouin distributed optical fiber sensors and the compensation method in the end-parts of the measurement range. A deflection measurement method for a beam subjected to a bending load using Brillouin distributed optical fiber sensors is also presented. This is verified by a three-point bending experiment employing an 8 m aluminum beam. The experimental results showed that the measured value agrees with the one expected by Brillouin measurement theory.