Fiber-Optic Bend Sensor Based on Double Cladding Fiber

Abstract

We develop and investigate fiber-optic bend sensor, which is formed by a section of double cladding SM630 fiber between standard SMF-28 fibers. The principle of operation of the sensor is based on coupling of the fiber core and cladding modes at the splices of fibers having different refractive index profiles. We use two sources with wavelengths 1328 and 1545 nm to interrogate the sensor. The dependences of transmission on curvature at these wavelengths are significantly different. We show that the proposed sensor is able to perform measurements of curvature with radii from meters to 26 cm with accuracy of about 3%.