Abstract
A novel approach for fiber optics 3D shape sensing, applicable to mini-invasive bio-medical devices, is presented. The approach exploits the optical backscatter reflectometry (OBR) and an innovative setup that permits the simultaneous spatial multiplexing of an optical fibers parallel. The result is achieved by means of a custom-made enhanced backscattering fiber whose core is doped with MgO-based nanoparticles (NP). This special NP-doped fiber presents a backscattering-level more than 40 dB higher with respect to a standard SMF-28. The fibers parallel is built to avoid overlap between NP-doped fibers belonging to different branches of the parallel, so that the OBR can distinguish the more intense backscattered signal coming from the NP-doped fiber. The system is tested by fixing, with epoxy glue, 4 NP-doped fibers along the length of an epidural needle. Each couple of opposite fibers senses the strain on a perpendicular direction. The needle is inserted in a custom-made phantom that simulates the spine anatomy. The 3D shape sensing is obtained by converting the measured strain in bending and shape deformation.
Highlights
The importance of shape sensing has significantly risen in the last decades, becoming a main research interest for the area of research, as well as for industrial necessities
The setup is divided in three main parts: an optical backscatter reflectometry (OBR), a fiber parallel composed by cuts of SMF-28 pigtails and cuts of NP-doped fiber arranged as explained in the previous section, and an epidural needle, which is the target of the shape sensing, properly sensorized with the fiber parallel
In the condition of straight needle, every fiber detects the strain on the needle in distributed points spaced by s, which is the sensor spacing set in the OBR, in the case under exam 2 mm
Summary
The importance of shape sensing has significantly risen in the last decades, becoming a main research interest for the area of research, as well as for industrial necessities. In this context the shape sensors based on optical fibers (FOSSs) present advantages with respect to conventional shape sensors (CSSs), having a particular applications niche where precise measurements and minimal invasive sensors are required [1]. Among the number of advantages shown by FOSSs, it is possible to underline that fiber sensors present a small form factor and a light weight (diameter of 125 μm or less), high sensitivity to temperature and strain, and chemical inertness [9,10]. The intrinsic small size of FOSSs is associated to the possibility to implement multi-point or distributing sensing so that the interrogation unit can be placed in a remote place without the necessity of complicated and bulky wiring and connections [12,13]
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