Curved elastic beam with opposed fiber-Bragg gratings for measurement of large displacements with temperature compensation

In this paper, a temperature-compensated configuration for extending the working range of fiber-Bragg grating (FBG) strain sensors has been proposed. This technique consists of the application of two FBGs to the opposite surfaces of a straight elastic beam which was bent in a horizontal direction. The difference of the two FBGs' wavelengths depends on the beam curvature, while the mean value is taken in order to compensate for the temperature effects. The sensor proposed is less fragile than the bare fiber and seems particularly suited as large displacement sensor, and for structures in which it is impossible to affix the bare fiber, such as breaks or separate elements.