We propose a setup for multiplexed distributed optical fiber sensors capable of resolving temperature distribution in thermo-therapies, with a spatial resolution of 2.5 mm over multiple fibers interrogated simultaneously. The setup is based on optical backscatter reflectometry (OBR) applied to optical fibers having backscattered power significantly larger than standard fibers (36.5 dB), obtained through MgO doping. The setup is based on a scattering-level multiplexing, which allows interrogating all the sensing fibers simultaneously, thanks to the fact that the backscattered power can be unambiguously associated to each fiber. The setup has been validated for the planar measurement of temperature profiles in ex vivo radiofrequency ablation, obtaining the measurement of temperature over a surface of 96 total points (4 fibers, 8 sensing points per cm 2). The spatial resolution obtained for the planar measurement allows extending distributed sensing to surface, or even three-dimensional, geometries performing temperature sensing in the tissue with millimeter resolution in multiple dimensions.

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.

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Wearable light textiles are gaining widespread interest in application for measurement and monitoring of biophysical parameters. Fiber optic sensors, in particular Bragg Grating (FBG) sensors, can be a competitive method for monitoring of respiratory behavior for chest and abdomen regions since the sensors are able to convert physical movement into wavelength shift. This study aims to show the performance of elastic belts with integrated optical fibers during the breathing activities done by two volunteers. Additionally, the work aims to determine how the positions of the volunteers affect the breathing pattern detected by optical fibers. As a reference, commercial mobile application for sensing vibration is used. The obtained results show that the FBGs are able to detect chest and abdomen movements during breathing and consequently reconstruct the breathing pattern. The accuracy of the results varies for two volunteers but remains consistent.

The high demand in effective and minimally invasive cancer treatments, namely thermal ablation, leads to the demand for real-time multi-dimensional thermometry to evaluate the treatment effectiveness, which can be also assisted by the use of nanoparticles. We report the results of 20-nm gold and magnetic iron oxide nanoparticles-assisted laser ablation on a porcine liver phantom. The experimental setup consisting of high-scattering nanoparticle-doped fibers was operated by means of a scattering-level multiplexing arrangement and interrogated via optical backscattered reflectometry, together with a solid-state laser diode operating at 980 nm. The multiplexed 2-dimensional fiber arrangement based on nanoparticle-doped fibers allowed an accurate superficial thermal map detected in real-time. Laser ablation (LA) is a minimally invasive and alternative thermal therapy technique to the surgical resection for the treatment of cancer that aimed to destroy the tumor at high temperatures. Laser ablation works on the principle of conversion of absorbed laser light into heat in tissue leading to coagulative necrosis. The laser light inside the tumor is distributed according to the phenomena of scattering, absorption, and bending. The rate of absorption mainly depends on the water and hemoglobin load 1. The widely employed laser types for LA are Neodymium: Yttrium aluminum garnet operating at a wavelength of 1,064 nm and solid-state diode working at a wavelength of 800-980 nm due to the best light penetration ability at near-infrared region 2. However, currently, laser diodes gaining more interest and replacing the Nd: YAG laser because they are cheaper, easier to transport due to the lightweight and shows the similar tissue penetration performance at the wavelengths between 800 and 980 nm 3. In the last 4 decades, many studies have investigated the efficacy of LA for the treatment of cancer, demonstrated its advances, and evaluated the settings responsible for the therapy outcome. Indeed, the size of the heated area significantly depends on the laser power, laser wavelength, absorption features, optical properties of the biological tissue, and time of laser irradiation 4,5. In the clinical practice, laser light is delivered in different modalities depending on the location of the tumor and the desired thermal effect: deep-seated tumors in the liver 6,7 , pancreas 8,9 , brain 10 and other organs can be reached by thin optical applicators; superficial tumors like nonmelanoma skin cancer 11,12 , superficial bladder carcinoma 13 can be treated with external and non-invasive approaches. The pioneering work of laser application in tumor treatment was done by Bown in 1983 4. LA is mostly known as interstitial laser thermotherapy, where the light delivered by means of delivery fiber into the tumor, usually a large core fiber or a side-firing fiber ranging in diameter from 0.5 to 2.5 mm 14-16. The laser light is further converted into the thermal energy leading to the tumor damage. Nowadays, the reliable method of real-time