Review and Analysis of Peak Tracking Techniques for Fiber Bragg Grating Sensors

Fiber Bragg Grating (FBG) sensors are among the most popular elements for fiber optic sensor networks used for the direct measurement of temperature and strain. Modern FBG interrogation setups measure the FBG spectrum in real-time, and determine the shift of the Bragg wavelength of the FBG in order to estimate the physical parameters. The problem of determining the peak wavelength of the FBG from a spectral measurement limited in resolution and noise, is referred as the peak-tracking problem. In this work, the several peak-tracking approaches are reviewed and classified, outlining their algorithmic implementations: the methods based on direct estimation, interpolation, correlation, resampling, transforms, and optimization are discussed in all their proposed implementations. Then, a simulation based on coupled-mode theory compares the performance of the main peak-tracking methods, in terms of accuracy and signal to noise ratio resilience

Advanced Interrogation of Fiber-Optic Bragg Grating and Fabry-Perot Sensors with KLT Analysis

The Karhunen-Loeve Transform (KLT) is applied to accurate detection of optical fiber sensors in the spectral domain. By processing an optical spectrum, although coarsely sampled, through the KLT, and subsequently processing the obtained eigenvalues, it is possible to decode a plurality of optical sensor results. The KLT returns higher accuracy than other demodulation techniques, despite coarse sampling, and exhibits higher resilience to noise. Three case studies of KLT-based processing are presented, representing most of the current challenges in optical fiber sensing: (1) demodulation of individual sensors, such as Fiber Bragg Gratings (FBGs) and Fabry-Perot Interferometers (FPIs); (2) demodulation of dual (FBG/FPI) sensors; (3) application of reverse KLT to isolate different sensors operating on the same spectrum. A simulative outline is provided to demonstrate the KLT operation and estimate performance; a brief experimental section is also provided to validate accurate FBG and FPI decoding

Performance analysis of a noncontact plastic fiber optical fiber displacement sensor with compensation of target reflectivity

peer-reviewedAn inexpensive fiber-based noncontact distance sensor specific for monitoring short-range displacements in micromachining applications is presented. To keep the overall costs low, the sensor uses plastic optical fibers and an intensiometric approach based on the received light intensity after the reflection from the target whose displacement has to be measured. A suitable target reflectivity compensation technique is implemented to mitigate the effects due to target surface nonuniformity or ageing.The performances of the sensor are first evaluated for different fiber configurations and target reflectivity profiles and positions using a numerical method based on Monte Carlo simulations. Then, experimental validations on a configuration designed to work up to 1.5mm have been conducted. The results have confirmed the validity of the proposed sensor architecture, which demonstrated excellent compensation capabilities, with errors below 0.04mm in the (0-1)mm range regardless the color and misalignment of the target

Correction: Schena, E.; et al. Fiber Optic Sensors for Temperature Monitoring during Thermal Treatments: an Overview

The author wishes to make the following correction to this paper [1], and to replace Figure 2:[...

Multiplexing techniques and applications in fiber-optic spatially resolved sensing networks

International audienceDistributed sensing, based on Rayleigh scattering or arrays of reflectors, can be extended as a multi-fiber, multi-sensor technique by using multiplexing features. Current research has overcome the time-and wavelength-division multiplexing, that has represented the golden standard for fiber Bragg gratings. In this work, we introduce novel domain that allow "parallel" multiplexing applied to distributed sensors, and are routed in the use of specialty fibers. The use of fibers doped with MgO-doped nanoparticles, as well as polymethyl methacrylate fibers, enables new domains for multiplexing, that are discussed in this work. Scattering-level, polarization, and sensitivity based multiplexing are discussed and applied to strain, temperature, and refractive index measurements

Distributed fiber optics 3D shape sensing by means of high scattering NP-doped fibers simultaneous spatial multiplexing

International audienceA 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

Application of nanoparticles and nanomaterials in thermal ablation therapy of cancer

Cancer is one of the major health issues with increasing incidence worldwide. In spite of the existing conventional cancer treatment techniques, the cases of cancer diagnosis and death rates are rising year by year. Thus, new approaches are required to advance the traditional ways of cancer therapy. Currently, nanomedicine, employing nanoparticles and nanocomposites, offers great promise and new opportunities to increase the efficacy of cancer treatment in combination with thermal therapy. Nanomaterials can generate and specifically enhance the heating capacity at the tumor region due to optical and magnetic properties. The mentioned unique properties of nanomaterials allow inducing the heat and destroying the cancerous cells. This paper provides an overview of the utilization of nanoparticles and nanomaterials such as magnetic iron oxide nanoparticles, nanorods, nanoshells, nanocomposites, carbon nanotubes, and other nanoparticles in the thermal ablation of tumors, demonstrating their advantages over the conventional heating methods

Temperature profiling of ex-vivo organs during ferromagnetic nanoparticles-enhanced radiofrequency ablation by fiber Bragg grating arrays

In this paper, we present real-time profiles of temperature during a ferromagnetic nanoparticles (NPs)enhanced radiofrequency ablation (RFA). A minimally invasive RFA setup has been prepared and applied ex vivo on a liver phantom; NPs (with concentration of 5 mg/mL) have been synthetized and injected within the tissue prior to perform the ablation, in order to facilitate the heat distribution to the peripheral sides of the ablated tissue. Temperature detection has been realized in situ with a network of 15 fiber Bragg grating (FBG) sensors in order to highlight the impact of the NPs on the RFA mechanism. Obtained temperature profiles and thermal maps confirm that nanoparticles injection ensures better heat penetration than in case of pristine RFA procedure. The results show that adding NPs solution leads to extending the successfully ablated area achieving a double-sized lesion

Design of a smartphone plastic optical fiber chemical sensor for hydrogen sulfide detection

We present a low-cost, handheld plastic optical fiber (POF) sensor for hydrogen sulfide (H2S) detection integrated onto a smartphone. The sensor uses smartphone flashlight as a source and camera as a pixel-based intensity detector. The POF is interconnected to the smartphone with a 3-D-printed connector on both source/detector sides. The sensing mechanism is embedded in the fiber link, making the system an all-fiber smartphone architecture. A mobile application handles data acquisition on the Android operative system. The sensor is functionalized for H2S detection through silver deposition on the POF outer surface. Experiments demonstrate the feasibility of the sensor system as the presence of H2S is successfully measured through an increase of optical losses through the POF link. This cost-effective, scalable, and compact sensor is promising for application in environmental sensing

Towards inline spatially resolved temperature sensing in thermal ablation with chirped fiber Bragg grating

We investigate the theory and feasibility of an in-line spatially resolved temperature sensor, suitable for thermal ablation monitoring. The sensor is based o a chirped fiber Bragg grating (CFBG). The CFBG is modelled as a chain of Bragg gratings, each sensitive to local temperature variations. By using a combination of iterative and statistical optimization techniques, it is possible to use demodulate the CFBG, in case of a Gaussian-like spatial temperature profile. A feasibility test based on CFBG simulation shows that the CFBG returns error <1 mm on cells damage threshold spatial estimation and good noise resilience