Evaluation of the fiber optic curvature sensor design parameters for new measurement approach application

In this paper, the influence of sensitive zone design parameters on the performance of fiber optic curvature sensor (FOCS) with sensitive zone made of V-grooves is experimentally investigated. A new insight into FOCS operation is given by introducing optical mode converter and CCD sensor into experimental setup, thus enabling mode-dependent analysis of V-grooves depth and spacing influence on sensor sensitivity and providing increased measurement reliability. Based on experimental analysis conducted in this work it is shown that FOCS intensity sensitivity increases approximately linear with sensitive zone depth and length, with highest sensitivity obtained for low order modes. According to this mode-dependent analysis, a new and more reliable measurement approach based on measurement of changes in the width of the output light distribution, rather than intensity, is proposed and tested. FOCS FWHM sensitivity increases approximately linear with depth and length of the sensitive zone, with higher sensitivity obtained in case of convex deformation. However, better linearity and balanced FWHM response is obtained for lower depths and shorter lengths of sensitive zone.