Intensity-modulated deformation sensor

Abstract

The true/apparent strain ambiguity associated with structurally embedded sensors of strain can be avoided with a novel sensor that measures deformation curvature. This fiber optic sensor is intensity modulated. Suitable fiber treatment enables the sensitivity to relate selectively to deformation about a preferential axis. With the addition of an inexpensive light-loss measuring system, a device is achieved which can readily interface with a computer. In the case of structural thicknesses below 1 cm, the proposed sensor exceeds the sensitivity of resistive strain gauges, especially along the neutral axis where strain cannot be measured in bending. Since strain and curvature are functionally related, either one can usually be deduced from the knowledge of the other. Distributed curvature measurements are possible and sensors can be tailor-made for a particular vibration mode in order to achieve modal decoupling.