Novel temperature-insensitive fiber Bragg grating sensor for displacement measurement

A novel temperature-insensitive displacement sensor based on a fiber Bragg grating (FBG) is presented. A FBG is glued onto the surface of a specially designed cantilever beam. It is found that the bandwidth of the FBG's reflection spectrum changes linearly with the variation of the displacement at the free end of the beam due to the displacement-induced strain gradient. Displacement sensing is realized by measuring the bandwidth of the signal from the FBG using an optical spectrum analyzer (OSA). Linear response of 0.058 nm mm−1 was obtained within a displacement range of 0–20 mm. This sensor is temperature independent due to the temperature-independent nature of the double-peak structure of the reflection spectrum.