Abstract

High spatial resolution and sensitivity are required in distributed strain measurements for structural health monitoring. In this paper we show that the distributed strain measurements with the high spatial resolution can be implemented by optical frequency domain reflectometry (OFDR). We could easily map the strain profile along a long gauge FBG from a spectrogram by applying Fourier transform analysis with a sliding window to the signal obtained from the measurement system. The OFDR signal can be simulated by the transfer matrix method based on coupled mode theory. We evaluated the spatial resolution and the sensitivity from the results of simulations and experiments. We confirmed that the spatial resolution of the current system is about 4 mm and it may be changed according to the location of the grating in the sensing fiber. In addition, the strain distribution adjacent to holes of an aluminum tensile specimen was measured. The agreement between this experimental result and the simulated one was good.

© 2006 IEICE