Polymer Optical Fiber Research Articles

Polymer-Based Optical Guided-Wave Biomedical Sensing: From Principles to Applications

Polymer-based optical sensors represent a transformative advancement in biomedical diagnostics and monitoring due to their unique properties of flexibility, biocompatibility, and selective responsiveness. This review provides a comprehensive overview of polymer-based optical sensors, covering the fundamental operational principles, key insights of various polymer-based optical sensors, and the considerable impact of polymer integration on their functional capabilities. Primary attention is given to all-polymer optical fibers and polymer-coated optical fibers, emphasizing their significant role in “enabling” biomedical sensing applications. Unlike existing reviews focused on specific polymer types and optical sensor methods for biomedical use, this review highlights the substantial impact of polymers as functional materials and transducers in enhancing the performance and applicability of various biomedical optical sensing technologies. Various sensor configurations based on waveguides, luminescence, surface plasmon resonance, and diverse types of polymer optical fibers have been discussed, along with pertinent examples, in biomedical applications. This review highlights the use of biocompatible, hydrophilic, stimuli-responsive polymers and other such functional polymers that impart selectivity, sensitivity, and stability, improving interactions with biological parameters. Various fabrication techniques for polymer coatings are also explored, highlighting their advantages and disadvantages. Special emphasis is given to polymer-coated optical fiber sensors for biomedical catheters and guidewires. By synthesizing the latest research, this review aims to provide insights into polymer-based optical sensors’ current capabilities and future potential in improving diagnostic and therapeutic outcomes in the biomedical field.

Integrative approach to fluorescence-based oxygen sensing in polymer optical fibers with surface plasmon resonance

This study demonstrates a technique to enhance oxygen (O2) concentration measurement by combining surface plasmon resonance (SPR) and fluorescence-based sensor on polymer optical fiber (POF). The SPR was generated using silver (Ag) and the fluorescence was generated by organic dye. Three fluorescence dyes were used, Tris (4, 7-diphenyl-1, 10-phenanthroline) ruthenium (II) dichloride ([Ru(dpp)3]2+), platinum octaethylporphyrin (PtOEP) and 5,10,15,20-tetrakis (pentafluorophenyl) 21 H,23H-porphine palladium (II) (PdTFPP). The sensor was tested in a gas chamber with different concentration level of O2. Sensitivity values for the fluorescence dyes for [Ru(dpp)₃]²⁺, PtOEP, and PdTFPP were 0.0099 a.u/%, 0.0343 a.u/% and 0.05 a.u/% respectively. When SPR was implemented, the sensitivity values for Ag/[Ru(dpp)₃]²⁺, Ag/PtOEP, and Ag/PdTFPP were 0.0589 nm/%, 0.0345 nm/%, and 0.118 nm/% respectively. PdTFPP and Ag/PdTFPP exhibit highest sensitivity in each experiment. Therefore, the further analysis for the sensing performance of PdTFPP and Ag/PdTFPP were held. As a result, Ag/PdTFPP exhibits lower limit of detection (LOD), and limit of quantification (LOQ) with 3.054 % and 9.254 %, respectively, with higher R2 of 0.9971 and lower mean standard deviation of 0.174, compared to PdTFPP 16.496 % and 49.988 % respectively, with R2 of 0.9211 and higher mean standard deviation of 2.003. This improvement can benefit researchers and professionals in medical diagnostics, environmental monitoring, and industrial process control by providing a more sensitive and accurate method for measuring O2 levels.

Solution Doping of PMMA-Based Step-Index Polymer Optical Fibers by Rhodamine B Near Glass Transition Temperature of PMMA

Solution doping is a facile approach to fabricating photoactive polymer optical fibers (POFs). However, previous studies reveal that only the cladding of step-index POFs can be doped by the solution doping method in methanol or aqueous solutions, whereas the fiber core is hardly doped. To dope the fiber core as well as the cladding, this study attempts to dope PMMA-based step-index POFs by raising the doping temperatures to near the Tg of PMMA. The results show that a considerable amount of rhodamine B (RhB) is doped in the fiber core, though the amount is still much less than that in the cladding. The highest content in the fiber core is 0.479 mg/g, which is achieved by doping the POFs in water at 110 °C for 8 h. At the same condition, the RhB content of the cladding is 11.5 mg/g. It is found that the high-temperature doping process leads to dramatic axial shrinkage and radial expansion of the POFs, due to the relaxation of the fiber core. The wrinkled cladding after doping suggests that the macromolecule orientation of the core is much higher than that of the cladding, and high orientation should be the main reason why the core is much more difficult to dope than the cladding. Additionally, the doping process at 90 °C in water does not increase the fiber loss regardless of the tremendous POF structure change. In short, the core of PMMA-based step-index POFs can be doped at a temperature near the Tg of the PMMA, making the solution doping technique more practicable for POF doping.

A novel optical acoustic fabric based on intensity-modulated flexible air-filled fiber adapter for sound sensing

This study proposes and demonstrates an optical acoustic fabric design method to detect sound, which is based on intensity-modulated flexible air-filled fiber adapter (FAFFA). A FAFFA was woven into the weft center of the polyamide fabric as weft, and the FAFFA was realized by connecting polymer optical fibers at each end of an flexible tube. The principle of the optical acoustic fabric is to allow the flexible tube to deform with the resonance of the polyamide fabric, subsequently changing the light intensity in the FAFFA. The macro-scale finite element method and ray tracing optical simulation investigated the operating principle of optical acoustic fabric and performance of FAFFA structures, and the influence of fabric parameters was evaluated by meso-scale finite element simulation. The yarn of the optical fiber acoustic fabric has low Young’s modulus and high flexibility. The proposed FAFFA structure is simple to prepare and has good maneuverability, which breaks away from the constraints of the traditional optical acoustic sensor membrane structure. This proposed optical acoustic fabric is easy to prepare, simple in principle and highly flexible. Along with wireless devices, the use of the optical acoustic fabric can be further extended to “hearing aids” for special individuals in wearable applications.

Influence of the core shape on the quality of fiber sensors based on D-shape fiber

Typical optical sensors based on D-shape fibers use standard step-index single-mode fibers (SMF) with a circular core. Multi-mode fibers, fibers with elliptical or rectangular cores, and photonic crystal fibers (PCF) are also used to achieve the best possible sensor performance. However, since the presented sensors differ not only in geometry but, most importantly, in the materials and core sizes, it is difficult to compare their properties directly. In this paper, we numerically analyzed the influence of the shape and size of the core on the sensing performance, with all other relevant parameters being equal. Full Text: PDF References D. Jauregui-Vazquez, J. P. Korterik, C. E. Osornio-Martinez, J. M. Estudillo-Ayala, H. L. Offerhaus, J. A. Alvarez-Chavez, "A strain reflection-based fiber optic sensor using thin core and standard single-mode fibers", Opt. Comm. 522, 128659 (2022). CrossRef H. H. Liu, D. J. Hu, Q. Z. Sun, L. Wei, K. W. Li, C. Liao, B. Li, C. Zhao, X. Dong, Y. Tang, Y. Xiao, G. Keiser, P. Shum, "Specialty optical fibers for advanced sensing applications", Opto-Electron Sci. 2(2), 220025 (2023). CrossRef K. Gasior, T. Martynkien, P. Mergo, W. Urbanczyk, "Fiber-optic surface plasmon resonance sensor based on spectral phase shift interferometric measurements", Sensors and Actuators B: Chemical 257, 602 (2018). CrossRef Y. Ying, G. Si, F. Luan, K. Xu, Y. Qi, H. Li, "Recent research progress of optical fiber sensors based on D-shaped structure", Opt. & Laser Techn. 90, 149 (2017). CrossRef J. Homola, Surface Plasmon Resonance Based Sensors (Berlin, Springer 2006). CrossRef K. Gasior, T. Martynkien., M. Napiorkowski, K. Zolnacz, P. Mergo, W. Urbanczyk, "A surface plasmon resonance sensor based on a single mode D-shape polymer optical fiber", J. Opt. 19, 025001 (2017). CrossRef Q. Wang, W. M. Zhao, "A comprehensive review of lossy mode resonance-based fiber optic sensors", Opt. Lasers in Engineering 100, 47 (2018). CrossRef K. Gasior, T. Martynkien, G. Wojcik, P. Mergo, W. Urbanczyk, "D-shape polymer optical fibres for surface plasmon resonance sensing", Opto-Electron. Rev. 24(4), 209 (2016). CrossRef G. Stepniewski, A. Filipkowski, D. Pysz, J. Warszewski, R. Buczynski, M. Smietana, R. Kasztelanic, "From D-shaped to D-shape optical fiber – A universal solution for sensing and biosensing applications: Drawn D-shape fiber and its sensing applications", Measurement 222, 113642 (2023). CrossRef R. Kasztelanic, H. T. Nguyen, D. Pysz, H. Thienpont, T. Omatsu, R. Buczynski, "Free-Form Optical Fiber with a Square Mode and Top-HatIntensity Distribution", Adv. Science 11, 2402886 (2024). CrossRef J.W. Fleming, "Dispersion in GeO2-SiO2 glasses", Appl. Opt. 23, 4486-4493 (1984). CrossRef T.A. König, P.A. Ledin, J. Kerszulis, M.A. Mahmoud, M.A. El-Sayed, J.R. Reynolds, V.V. Tsukruk., "Electrically Tunable Plasmonic Behavior of Nanocube–Polymer Nanomaterials Induced by a Redox-Active Electrochromic Polymer", ACS Nano 8, 6182-6192 (2014). CrossRef I.Z. Kozma, P. Krok, E. Riedle, "Direct measurement of the group-velocity mismatch and derivation of the refractive-index dispersion for a variety of solvents in the ultraviolet", J. Opt. Soc. Am. B 22, 1479-1485 (2005). CrossRef

An Intensity-Variation Technique for Dual-Point Liquid Level Measuring Sensor Utilizing Polymer Optical Fiber

An Intensity-Variation Technique for Dual-Point Liquid Level Measuring Sensor Utilizing Polymer Optical Fiber

Optical fibre based artificial compound eyes for direct static imaging and ultrafast motion detection

Natural selection has driven arthropods to evolve fantastic natural compound eyes (NCEs) with a unique anatomical structure, providing a promising blueprint for artificial compound eyes (ACEs) to achieve static and dynamic perceptions in complex environments. Specifically, each NCE utilises an array of ommatidia, the imaging units, distributed on a curved surface to enable abundant merits. This has inspired the development of many ACEs using various microlens arrays, but the reported ACEs have limited performances in static imaging and motion detection. Particularly, it is challenging to mimic the apposition modality to effectively transmit light rays collected by many microlenses on a curved surface to a flat imaging sensor chip while preserving their spatial relationships without interference. In this study, we integrate 271 lensed polymer optical fibres into a dome-like structure to faithfully mimic the structure of NCE. Our ACE has several parameters comparable to the NCEs: 271 ommatidia versus 272 for bark beetles, and 180o field of view (FOV) versus 150–180o FOV for most arthropods. In addition, our ACE outperforms the typical NCEs by ~100 times in dynamic response: 31.3 kHz versus 205 Hz for Glossina morsitans. Compared with other reported ACEs, our ACE enables real-time, 180o panoramic direct imaging and depth estimation within its nearly infinite depth of field. Moreover, our ACE can respond to an angular motion up to 5.6×106 deg/s with the ability to identify translation and rotation, making it suitable for applications to capture high-speed objects, such as surveillance, unmanned aerial/ground vehicles, and virtual reality.

Pollen-based natural nanostructures to realize nanoplasmonic biochips for single-molecule detection

In this work, a paradigm change in the development of the plasmonic-based bio/chemical sensing approaches is presented. The proposed idea is to use natural nanostructures instead of those fabricated by electron-beam lithography (EBL) tools. This sensing approach produces several advantages, such as high performances without an optimization step and a simple, low-cost, and eco-friendly production process with respect to other methods, which are still time-consuming with low scalability. In particular, pollen's nanostructures covered by gold nanofilms are used to realize gold nanogratings (GNG), similar to those made via EBL, to excite hybrid plasmonic phenomena. Bulk and binding sensitivities are evaluated and compared to nanoplasmonic sensors, particularly those achieved via an EBL-based chip. As proof of principle, an estrogen receptor (ERα) is immobilized on the plasmonic nanostructured surfaces of both EBL-based and pollen-based chips and interrogated by the same custom 3D-printed holder through a transmission-based experimental setup, exploiting polymer optical fibers (POFs). The experimental results demonstrate that the proposed pollen-based nanoplasmonic biosensor shows performance very similar to an EBL-based nanoplasmonic biosensor, indicating the equivalence between the two nanoplasmonic biosensors. The biosensor exhibited a detection limit better than 1 aM for the estradiol, demonstrating the capabilities of the proposed sensing approach towards single-molecule detection.

Citrate polymer optical fiber for measuring refractive index based on LSPR sensor

Fiber optic localized surface plasmon resonance (LSPR) sensors have become an effective tool in refractive index (RI) detection for biomedical applications because of their high sensitivity. However, using conventional optical fiber has caused limitations in implanting the sensor in the body. This research presents the design and construction of a new type of polymer-based LSPR sensors to address this issue. Also, finite element method (FEM) is used to design the sensor and test it theoretically. The proposed polymer optical fiber (POF) based on citrate is biocompatible, flexible, and degradable, with a rate of 22% and 27 over 12 days. The step RI structure utilizes two polymers for light transmission: poly (octamethylene maleate citrate) (POMC) as the core and poly (octamethylene citrate) (POC) as the cladding. The POF core and cladding diameters and lengths are 700 µm, 1400 µm, and 7 cm, respectively. The coupling efficiency of light to the POF was enhanced using a microsphere fiber optic tip. The obtained results show that the light coupling efficiency increased to 77.8%. Plasma surface treatment was used to immobilize gold nanoparticles (AuNPs) on the tip of the POF, as a LSPR-POF sensor. Adsorption kinetics was measured based on the pseudo-first-order model to determine the efficiency of immobilizing AuNPs, in which the adsorption rate constant (k) was obtained be 8.6 × 10–3 min−1. The RI sensitivity of the sensor in the range from 1.3332 to 1.3604 RIU was obtained as 7778%/RIU, and the sensitivity was enhanced ~ 5 times to the previous RI POF sensors. These results are in good agreement with theory and computer simulation. It promises a highly sensitive and label-free detection biosensor for point-of-care applications such as neurosciences.

High pressure sensor based on intensity-variation using polymer optical fiber

Silica fiber under high pressure increases the risk of fiber breakage or permanent deformation, which may cause sensor failure due to mechanical strength limitations. High pressure can also induce birefringence in optical fiber. In this study, we present a simple design and low-cost high pressure sensor using polymer optical fiber (POF) based on the intensity-variation technique. A side-coupling mechanism in the sensor structure is adopted, which varies the intensity with applied pressure. Two POFs are twisted together to create a sensing region where the light is launched in the first fiber and measurement is taken from the second fiber. In sensing phenomena, cladding mode frustrated total internal reflection occurs when pressure increases. Silicone gel is used in the pressure chamber for sealing and preventing leakage. The sensor structure is able to detect high pressure in the MPa range, where we tested up to 4 MPa. For higher sensitivity, twisted and bend structure is analyzed, and sensitivity is achieved at about 432.21 nW/MPa. However, twisted helical structure is adopted to enhance sensing range which is about 50 cm. The proposed high-pressure sensor structure is easier to fabricate and has high stability because it doesn’t require any destructive method as compared to other conventional methods.

A 1 × 8 Optical Splitter Based on Polycarbonate Multicore Polymer Optical Fibers.

Visible light communication (VLC) is becoming more relevant due to the accelerated advancement of optical fibers. Polymer optical fiber (POF) technology appears to be a solution to the growing demand for improved transmission efficiency and high-speed data rates in the visible light range. However, the VLC system requires efficient splitters with low power losses to expand the optical energy capability and boost system performance. To solve this issue, we propose an effective 1 × 8 optical splitter based on multicore polycarbonate (PC) POF technology suitable for functioning in the green-light spectrum at a 530 nm wavelength. The new design is based on replacing 23 air-hole layers with PC layers over the fiber length, while each PC layer length is suitable for the light coupling of the operating wavelength, which allows us to set the right size of each PC layer between the closer PC cores. To achieve the best result, the key geometrical parameters were optimized through RSoft Photonics CAD suite software that utilized the beam propagation method (BPM) and analysis using MATLAB script codes for finding the tolerance ranges that can support device fabrication. The results show that after a light propagation of 2 mm, an equally green light at a 530 nm wavelength is divided into eight channels with very low power losses of 0.18 dB. Additionally, the splitter demonstrates a large bandwidth of 25 nm and stability with a tolerance range of ±8 nm around the operated wavelength, ensuring robust performance even under laser drift conditions. Furthermore, the splitter can function with 80% and above of the input signal power around the operated wavelength, indicating high efficiency. Therefore, the proposed device has a great potential to boost sensing detection applications, such as Raman spectroscopic and bioengineering applications, using the green light.

Mechanically Robust Biopolymer Optical Fibers with Enhanced Performance in the Near-Infrared Region.

Polymer optical fibers (POFs) are lightweight, fatigue-tolerant, and suitable for local area networks, automobiles, aerospace, smart textiles, supercomputers, and servers. However, commercially available POFs are exclusively fabricated using synthetic polymers derived from nonrenewable resources. Recently, attempts have been made to fabricate biocompatible and biopolymeric optical fibers. However, their limitations in mechanical performance, thermal stability, and optical properties foil practical applications in waveguiding. Here, we report a comprehensive study of the preparation of biopolymer optical fibers with tailored mechanical strength, thermal properties, and their short-distance applications. Specifically, we use alginate as one of the key components with methylcelluloses to promote readily scalable wet spinning at ambient conditions to fabricate 21 combinations of composite fibers. The fibers display high maximum strain (up to 58%), Young's modulus (up to 11 GPa), modulus of toughness (up to 63 MJ/m3), and a high strength (up to 195 MPa), depending on the composition and fabrication conditions. The modulus of toughness is comparable to that of glass optical fibers, while the maximum strain is nearly 15 times higher. The mechanically robust fibers with high thermal stability allow rapid humidity, touch sensing, and complex shapes such as serpentine, coil, or twisted structures without losing their light transmission properties. More importantly, the fibers display enhanced optical performance and sensitivity in the near-infrared (NIR) region, making them suitable for advanced biomedical applications. Our work suggests that biobased materials offer innovative solutions to create short-distance optical fibers from fossil fuel-free resources with novel functionalities.

Efficient CO2 Conversion through a Novel Dual-Fiber Reactor System.

Carbon dioxide (CO2) can be converted to valuable organic chemicals using light irradiation and photocatalysis. Today, light-energy loss, poor conversion efficiency, and low quantum efficiency (QE) hamper the application of photocatalytic CO2 reduction. To overcome these drawbacks, we developed an efficient photocatalytic reactor platform for producing formic acid (HCOOH) by coating an iron-based metal-organic framework (Fe-MOF) onto side-emitting polymeric optical fibers (POFs) and using hollow-fiber membranes (HFMs) to deliver bubble-free CO2. The photocatalyst, Fe-MOF with amine-group (-NH2) decoration, provided exceptional dissolved inorganic carbon (DIC) absorption. The dual-fiber system gave a CO2-to-HCOOH conversion rate of 116 ± 1.2 mM h-1 g-1, which is ≥18-fold higher than the rates in photocatalytic slurry systems. The 12% QE obtained using the POF was 18-fold greater than the QE obtained by a photocatalytic slurry. The conversion efficiency and product selectivity of CO2-to-HCOOH were up to 22 and 99%, respectively. Due to the dual efficiencies of bubble-free CO2 delivery and the high QE achieved using the POF platform, the dual-fiber system had energy consumption of only 0.60 ± 0.05 kWh mol-1, 3000-fold better than photocatalysis using slurry-based systems. This innovative dual-fiber design enables efficient CO2 valorization without the use of platinum group metals or rare earth elements.

A preliminary study of polymer optical fiber’s knittability for smart wear applications

PurposeThe purpose of this research is to ascertain the feasibility of fabricating polymer optical fibers (POFs) based textile structures by knitting with Polymethylmethacrylate (PMMA) based optical fibers for textile sensor application. It has long been established that by using the principles of physics, POFs have the capability to function as sensors, detecting strain, temperature and other variables. However, POF applications such as strain and pressure sensing using knitting techniques has since not been very successful due to a number of reasons. Commercially available PMMA-based optical fibers tend to be fragile and susceptible to breakages when subjected to stress during the knitting processes. Also light transmitted within these fibers is prone to leakage due to the curvature that results when optical fibers are interlaced or interlooped within fabric structures.Design/methodology/approachUsing Stoll’s multi-gauge CMS 350 HP knitting machine, five fabric structures namely, 1 × 4 float knit structure, tunnel inlay knit structure, 3:1 fleece fabric and 2:1 fleece fabric structure respectively were used to knit sensor samples. The samples were subsequently tested for length of illumination and sensitivity relative to applied pressure.FindingsThe results of this preliminary study establish that embedding plastic optical fibers into a knitted structure during the fabric formation process for soft strain sensor application possible. The best illumination performance was recorded for tunnel inlay structure which had an average of 94 cm course length of POF being illuminated. Sensor sensitivity experiments also establish that the relative spectral intensity of the fiber is sensitive to both light and pressure. Problems encountered and recommendations for further research have also been discussed and proffered.Research limitations/implicationsDue to resource limitations, an innovative technique (use of precision weight set) was used to apply pressure to the sensors. Consequently, information regarding the extent of corresponding sensor deformation has not been used in this initial analysis.Practical implicationsBecause the fundamental step toward finding a solution to any engineering problem is the acquisition of reliable data, and considering the fact that most of the popular technologies used for soft textile sensors are still bedeviled with the problem of signal instability and noise, the success of this application thus has the tendency to promote the wide spread adoption of POF sensors for smart apparel applications.Originality/valueAs far as research on soft strain sensors is concerned, to the best of the authors’ knowledge, this is the first study to have attempted to knit deformable sensors using commercially available POFs.

Influence of launch light beam conditions on the bandwidth in multimode graded-index microstructured POFs

The time-dependent power flow equation (TD PFE) is used to theoretically examine the wavelength dependency of the bandwidth in a multimode graded-index microstructured polymer optical fiber (GI mPOF) with a solid core. The TD PFE is numerically solved using the explicit finite difference method (EFDM) and physics-informed neural networks (PINNs). Our numerical results show that the bandwidth decreases with an increasing wavelength from 476 to 522 and finally to 568 nm. With further increasing of the wavelength from 568 to 633 nm, the bandwidth increases. In this way, we have demonstrated that the maximum bandwidth of the analyzed GI mPOF in the analyzed wavelength region is obtained at 633 nm. Such bandwidth behavior is a consequence of the different influences of the analyzed wavelengths on the parameters that characterize the refractive index distribution and the maximum propagating principal mode number of the analyzed GI mPOF. We also showed that, when the radial offset of the incident light beam increases, the bandwidth decreases. This results from a greater modal dispersion when higher guided modes are excited. As a result, based on the observations reported in this work, it is simpler to modify the GI mPOF for a particular application at various wavelengths.

Doped Epoxy Resins as an Alternative to Luminescent Optical Sensors

The main objective of the study was to prepare and then subject to thorough analysis photosensitive materials to determine their usability as materials for the production of special polymer optical fibers. A comparison of the physicochemical properties of compositions containing commercially available fluorescein with compositions doped with 2.7-dihydroxy naphthalene with epichlorohydrin (2.7-NAF.EP) was made. The degree of copolymer conversion, which is one of the most important parameters confirming the effectiveness of the curing method, was calculated based on ATR-FT-IR spectra. Additionally, in order to check the processing capabilities of the obtained compositions, a thorough thermal and spectroscopic analysis was performed (the best method used for this purpose is the coupled analysis technique (TG-DSC-MS)). The obtained results indicate that the photoluminescent properties of the dopants used were not suppressed after their introduction into the matrix. Thermal and spectroscopic analysis allowed us to determine the polymerization conditions in which the physicochemical properties of the obtained materials are the best from the optical fiber-technology point of view.

Distributed polymer optical fiber sensors using digital I-OFDR for geotechnical infrastructure health monitoring

We present a distributed polymer optical fiber sensor system for deformation monitoring of geotechnical infrastructure. The sensor system is based on the digital incoherent optical frequency domain reflectometry (I-OFDR) for the detection of local strain events along a perfluorinated polymer optical fiber (PF-POF) used as a sensing fiber. For the best possible load transfer, the PF-POFs were integrated onto geotextiles which pose a sensor carrier for the sensing fiber. By using elastic PF-POF instead of a standard glass fiber as a sensing fiber the strain range of geotextile-integrated fiber optic sensors could be extended up to 10 % in accordance with the end-user requirements. In order to reduce overall costs of the sensor system and achieve its robustness required for use on site, the standard vector network analyzer used by default was replaced by an integrated digital board for optical frequency domain analysis. This implementation showed a significant improvement in the dynamic range and sensitivity compared to the previous measurement system based on the conventional network analyzer. The functionality of the entire sensor system was proven in the field test during the installation of two geomats with integrated PF-POFs embedded into a road embankment in a section of the B 91 federal road near Werschen in the greater Leipzig area. To monitor the installation-related changes in the condition of both sensor-based geomats several control measurements on the embedded PF-POFs and co-integrated reference glass fibers were carried as the construction works progressed. The measurements recorded in the field confirm the great potential of the selected PF-POF used as the distributed fiber optic strain sensor. The future management of the remaining challenges of industrial strain-coupled sensor integration can result in a successful market launch of the PF-POF-sensor integrated into geosynthetics. The sensor system is ready to be used for practical application.

Improvement of fiber optic sensor measurement methods for temperature and humidity measurement in microelectronic circuits

A wide range of applications such as healthcare, human comfort, agriculture, food processing and storage, and electronics manufacturing also require fast and accurate measurement of humidity and temperature. Optical fiber-based sensors have several advantages over electronic sensors, and much research has been conducted in this area in recent years. This paper describes the current trends in fiber optic temperature and humidity sensors. The evolution of optical structures aimed at humidity detection is presented, as well as a new design of an optical sensor used for this purpose. The main methods of humidity determination using fiber-optic laser reflection based on Optical fiber humidity sensor (FPI) were analyzed and experimental results were obtained. Based on temperature-sensitive strain variation, a method for temperature determination based on the specific spectral back-reflection effect of fiber Bragg gratings (FBGs) is considered. Experimental analyses were conducted on the light reflection of humidity-sensitive agarose using optical fibers based on the Fabry-Perot Interferometer (FPI). It exhibits a good linear response to relative humidity, ranging from 25 % to 95 %. During temperature measurement, the deformation changes of the Fiber Bragg Grating fibers showed excellent performance, ranging from –5 °C to 70 °C. New structures, such as resonators, are being explored to improve the resolution of fiber optic temperature and humidity sensors. In addition, recent studies on polymer optical fibers show that the sensitivity of this type of sensor has not yet been achieved. Thus, materials sensitive to humidity and temperature still need to be investigated to improve sensitivity and resolution

AI-Assisted Insole Sensing System for Multifunctional Plantar-Healthcare Applications.

The pervasive global issue of population aging has led to a growing demand for health monitoring, while the advent of electronic wearable devices has greatly alleviated the strain on the industry. However, these devices come with inherent limitations, such as electromagnetic radiation, complex structures, and high prices. Herein, a Solaris silicone rubber-integrated PMMA polymer optical fiber (S-POF) intelligent insole sensing system has been developed for remote, portable, cost-effective, and real-time gait monitoring. The system is capable of sensitively converting the pressure of key points on the sole into changes in light intensity with correlation coefficients of 0.995, 0.952, and 0.910. The S-POF sensing structure demonstrates excellent durability with a 4.8% variation in output after 10,000 cycles and provides stable feedback for bending angles. It also exhibits water resistance and temperature resistance within a certain range. Its multichannel multiplexing framework allows a smartphone to monitor multiple S-POF channels simultaneously, meeting the requirements of convenience for daily care. Also, the system can efficiently and accurately provide parameters such as pressure, step cadence, and pressure distribution, enabling the analysis of gait phases and patterns with errors of only 4.16% and 6.25% for the stance phase (STP) and the swing phase (SWP), respectively. Likewise, after comparing various AI models, an S-POF channel-based gait pattern recognition technique has been proposed with a high accuracy of up to 96.87%. Such experimental results demonstrate that the system is promising to further promote the development of rehabilitation and healthcare.

Light transmission in knitted fabrics through polymeric optical fiber insertion for advanced textile applications

Smart textiles are prominent in the textile industry, with applications in various technical areas such as medicine, architecture, sports, and esthetic purposes, among others. Within this concept, optical fibers are classified as passive smart textiles and are highly attractive for clothing lighting and monitoring physiological parameters. This study aimed to present methods for inserting polymeric optical fibers into weft single knitted fabrics and verifying the loss of luminosity in them, analyzing the technical feasibility of developing e-textiles to be applied in monitoring. For such, weft knitted fabrics were produced by altering the optical fiber insertion methodology, defined as inlay insertion and insertion in the course direction, each subdivided into different methods. Light transmission was verified using a laser pen connected to the optical fiber. Images were captured and analyzed using LILP software to verify and quantify the loss of luminosity in each insertion method. Light transmission microscopy was performed to evaluate the surface of the polymeric optical fiber used. For the insertion techniques performed, inlay and by course direction, the result obtained for signal transmission was satisfactory; however, the inlay insertion methods presented lower light emission but lower luminosity loss than the insertion by course direction. This result is very interesting because it enables the development of weft knitted fabrics from the use of optical fibers for application in various types of monitoring.