Fiber-optic curvature sensor based on a core-offset structure

A fiber-optic curvature sensor based on a core-offset structure has been proposed and demonstrated in this paper. Here two core-offset jointing points have been inserted in the sensor. The first core-offset jointing point is used to excite the cladding modes and the second one is used as the interference point. We fix the core-offset structure based curvature sensor by two fiber holders which can be controlled precisely to control the bending curvature of the sensor. The fiber holder is adjusted for 20 μm per time with the total adjusted distance of 200 μm in this experiment. The experimental results show that the curvature sensor is very sensitive to bending change and the transmission spectrum of the sensor will shift to blue wavelength with the increasing of the bending curvature. The measured curvature sensitivity is -6.9 nm/m-1 with the sensor length of 55.6 mm. In order to study the influence of the fiber length, we fabricated three sensors with different fiber lengths. The experimental results show that the curvature sensitivity can be influenced by the length of the sensor and the curvature sensitivity will be increased with the increasing of the length of the sensor.