Shape measurement using a multicore optical fiber sensor with asymmetric dual cores

Abstract

Shape measurement by using multicore optical fiber sensor has attracted more attention in many fields due to the good consistency of the fiber cores. Three symmetrically arranged cores in multicore fiber are usually used for reconstructing shape by calculating the bending vectors, which will not be achieved when one of the cores is damaged or occupied in actual application. A shape measurement method using multicore optical fiber sensor with asymmetric dual cores is proposed in this paper. Based on analyzing the principle of shape reconstruction and the geometric relationship of asymmetric dual cores in multicore fiber sensor, the bending vector is decomposed. The mathematical expressions for bending curvature and orientation of asymmetric dual cores are derived. The two dimensional (2D) and three dimensional (3D) shape reconstruction results both in finite element modelling simulation and shape measurement experiment based on optical frequency domain reflectometry have shown that the proposed method using multicore fiber sensor with asymmetric dual cores is able to achieve shape measurement, and its performance is comparable and even equivalent to the traditional method by using three symmetrically arranged cores. In the experiment, the maximum relative errors of 2D and 3D reconstructed shapes are 2.653% and 5.139%, respectively. The proposed method, which only needs asymmetric dual cores in the multicore optical fiber sensor for shape reconstruction, will be conducive to solve the limitation of multicore optical fiber sensors in shape measurement applications.