Grooved fiber sensors for deformation imaging

We demonstrate the performance of a Guided-Path Tomography (GPT) sensor element, based on photonic technology, as part of a sensor head for tomography imaging of physical parameters on non-planar and possibly flexible surfaces. Novel in our approach is to image by measuring the waveguiding loss along a set of plastic optical fiber (POF) sensor elements, strategically arranged on the imaged surface, to allow tomography measurements and image reconstruction. To image small changes in the local surface curvature, the POF elements are sensitized by cutting transversal grooves along the fiber. The losses induced by bending the POF element are systematically studied for varying groove depth and for varying number of grooves, allowing the definition of calibration procedures as well as the operation envelope of the POF sensor and ultimately-the tomography imager. The mechanical integrity of the grooved POF sensor elements is demonstrated in experiments of controlled repetitive bending, representative of realistic conditions.