Displacement fiber Bragg grating sensor with temperature compensation

In this work 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. Pushing nearer of beam ends produced the beam curvature variation measured by means of the two FBG wavelength difference 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 sensitivity of the system was obtained for different beam lengths. Decreasing the beam length increases the sensitivity, but decreases the working range. The sensor proposed is less fragile than the bare fiber and constitutes a displacement sensor particularly suited for applications to breaks or separate elements of structures where it is impossible to affix the bare fiber.