Directional curvature sensor based on long period gratings in multicore optical fiber

Multicore optical fiber can be used to implement multidimensional optical fiber sensors including curvature sensors. In this paper, a selective core inscription technique is used in order to inscribe a single long period grating in each of the outer cores of the optical fiber. A set of three different long period gratings is inscribed for implementing the curvature sensor. The ability of the sensor for measuring the magnitude and the direction of curvature is demonstrated. The optical fiber sensor is characterized experimentally for curvature magnitudes from 0 m(-1) to 1.77 m(-1) and curvature directions from 0 to 360. The maximum curvature sensitivity of the developed sensor is -4.85 nm/m(-1).