Optical low-coherence reflectometry for deflection measurement with a fiber Bragg grating cantilever sensor

Optical low-coherence reflectometry (OLCR) for deflection measurement with a fiber Bragg grating (FBG) cantilever sensor is proposed and experimentally demonstrated to reveal the internal structure of the sensing fiber in correlation with its optical properties, which is the first report on a spatial-resolved technique to realize dynamic deflection measurement. The change in the fiber length during a convex or concave deflection of the cantilever sensor detected by OLCR achieves simultaneous determination of the magnitude and direction of the deflection by the use of a standard single-mode telecommunication fiber inscribed with single grating. The FBG plays a key role in selecting pre-strain set point and compensating the environmental temperature fluctuations. The experimental results are in good agreement with the theoretical analysis.