Fiber Optic Technique Research Articles

A systematic overview of strategies for photosensitizer and light delivery in antibacterial photodynamic therapy for lung infections.

Antimicrobial photodynamic therapy (aPDT) emerges as a viable treatment strategy for infections resistant to conventional antibiotics. A complex interplay of factors, including intracellular photosensitizer (PS) accumulation, photochemical reaction type, and oxygen levels, determines the efficacy of aPDT. Recent progress includes the development of modified PSs with enhanced lipophilicity and target-specific strategies to improve bacterial cell wall penetration and targeting. Nanotechnology-based approaches, such as using nanomaterials for targeted PS delivery, have shown promise in enhancing aPDT efficacy. Advancements in light delivery methods for aPDT, such as transillumination of large lesions and local light delivery using fiber optic techniques, are also being explored to optimize treatment efficacy in clinical settings. The limited number of animal models and clinical trials specifically designed to assess the efficacy of aPDT for lung infections highlights the need for further research in this critical area. The potential prospects of aPDT for lung tissue infections originating from antibiotic-resistant bacterial infections are also discussed in this review.

A Brief Review of Hemp Fiber Length Measurement Techniques

Accurate fiber length measurement is essential for the processing and quality management of textile products. This article reviews the current methods used to measure fiber length, including manual, photoelectric, capacitive, and optical techniques. Existing sample preparation processes for natural fiber characterization have been primarily developed for cotton and wool fibers. However, hemp fibers present unique challenges due to their greater length variability, high strength, and low elongation, making some traditional sample preparation methods less effective. Image processing offers a promising approach for scalable and precise measurement of hemp fiber length. Nevertheless, current image processing techniques are limited by the inability to effectively handle overlapping fibers, which increases both the time and cost of testing. Continued research into developing more advanced segmentation algorithms could lead to more widely adopted commercial methods for fiber measurement.

34 Videolaringoscopy as an usefull tool not only to assist fiberoptic bronchoscope technique, but also as a decision maker to extubate or not a difficult airway

34 Videolaringoscopy as an usefull tool not only to assist fiberoptic bronchoscope technique, but also as a decision maker to extubate or not a difficult airway

High-resolution monitoring of soil infiltration using distributed fiber optic

Monitoring the infiltration process in soil is of great importance in various fields. However, the majority of existing infiltration monitoring methods have certain limitations that hinder their ability to meet the technical requirements for continuous spatial monitoring of the infiltration process. To address this issue, this study proposes a new method for achieving spatially continuous monitoring of the infiltration process. This method employs the improved Active Heating Fiber Optics (AHFO) technique as the underlying mechanism and utilizes Optical Frequency Domain Reflectometry (OFDR) monitoring technology characterized by exceptionally high spatial resolution and monitoring sensitivity. The proposed method, referred to as Active Heating Optical Frequency Domain Reflectometry (AH-OFDR). The feasibility of AH-OFDR was validated through a set of experimental tests, involving the installation of optical fibers within cylindrical soil samples for infiltration monitoring. A comparison was conducted between the infiltration patterns obtained through AH-OFDR and those acquired using the well-established Distributed Temperature Sensing (DTS) method. Additionally, the temperature distribution within the sample during the infiltration process was monitored by employing infrared thermography technology. The experimental results demonstrated an excellent agreement between the infiltration patterns obtained through AH-OFDR and DTS, reaffirming the viability and accuracy of AH-OFDR for soil infiltration monitoring. However, when compared to DTS, AH-OFDR excels in achieving dynamic monitoring of water content variations at a spatial resolution as fine as the centimeter level, empowering high-resolution and continuous monitoring. The changes in the soil temperature field recorded by the infrared thermography system further confirm the accuracy of the AH-OFDR monitoring results.

Large scale monitoring of a highway bridge with remote sensing and distributed fiber optic techniques during load tests

Many bridges in western countries are at the end of their lifetime and hence Structural Health Monitoring is vital to ensure their safe operation. Load test are one way to assess the utilization grade and to decide if actions have to be taken. We report on a comprehensive monitoring campaign of load tests of a large highway bridge on the Brenner highway. The Brenner highway is the main alpine truck crossing passages from Germany to Italy. Several different remote sensing techniques like static and dynamic laser scanning, robotic total station measurements and interferometric radar were used to determine displacements of the bridge deck and girders. Strain changes and bending were observed with distributed fiber optic sensing. Furthermore, the movements of the bridge bearings were determined with IoT tilt sensors. Data was acquired during static and dynamic load tests. We demonstrate that the utilization grade of the bridge can be assessed by an integrated analysis of the different sensor data in combination with a numerical model of the structure. As a consequence of the investigations it was decided by the highway operator to close one of the three lanes of the bridge.

Application of Distributed Acoustic Sensing in Geophysics Exploration: Comparative Review of Single-Mode and Multi-Mode Fiber Optic Cables

The advent of fiber optic technology in geophysics exploration has grown in its use in the exploration, production, and monitoring of subsurface environments, revolutionizing the way data are gathered and interpreted critically to speed up decision-making and reduce expense and time. Distributed Acoustic Sensing (DAS) has been increasingly utilized to build relationships in complex geophysics environments by utilizing continuous measurement along fiber optic cables with high spatial resolution and a frequency response of up to 10 KHz. DAS, as fiber optic technology examining backscattered light from a laser emitted inside the fiber and measuring strain changes, enables the performance of subsurface imaging in terms of real-time monitoring for Vertical Seismic Profiling (VSP), reservoir monitoring, and microseismic event detection. This review examines the most widely used fiber optic cables employed for DAS acquisition, namely Single-Mode Fiber (SMF) and Multi-Mode Fiber (MMF), with the different deployments and scopes of data used in geophysics exploration. Over the years, SMF has emerged as a preferred type of fiber optic cable utilized for DAS acquisition and, in most applications examined in this review, outperformed MMF. On the other side, MMF has proven to be preferable when used to measure distributed temperature. Finally, the fiber optic cable deployment technique and acquisition parameters constitute a pivotal preliminary step in DAS data preprocessing, offering a pathway to improve imaging resolution based on DAS measurement as a future scope of work.

Fiber Optic Devices for Diagnostics and Therapy in Photomedicine

AbstractPhotonic technologies have made enormous impacts on modern medicine, advancing disease diagnostics and treatments as well as health monitoring. A long‐standing challenge in the use of light and its widespread effects in photomedicine is the finite penetration of light in tissues. However, judiciously engineered optical fibers helped overcome this challenge and advance light delivery to deep tissues with spatial precision and desired accessibility. In recent years, the development of photonic technologies including optical biomaterials, fiber functionalization, and biomedical device innovations has greatly expanded the scope of light‐based healthcare. Here, the fundamentals and materials of fiber optics to endow themselves with biocompatibility, flexibility, and diverse functionalities required for long‐term implantation are overviewed. The design strategies of lab‐on‐fiber techniques, operation requirements to construct fiber optic sensors, and their health monitoring applications as wearable and implantable devices are presented. The use of fiber optics in major light‐based therapeutic modalities including optogenetics, photodynamic therapy, photobiomodulation, photochemical cross–linking, and photothermal therapy is illustrated to enhance their effectiveness, specificity, and feasibility. In short, a comprehensive review is provided on the fiber optic techniques and the latest photonic devices, which are envisioned to evolve photomedicine in clinical and point‐of‐care practices.

Experimental Study on Spontaneous Combustion Monitoring in Coal Mine Airspace Based on Distributed Fiber Optic Temperature Measurement

ABSTRACT Spontaneous combustion fires in the mining airspace seriously affect safety at mines. It is crucial to accurately predict the location of fire sources and forecast spontaneous combustion disasters. This study, therefore, proposes an intuitive, accurate, and efficient distributed fiber optic temperature measurement technique for detecting spontaneous coal combustion. To overcome the limitations of using traditional optical fibers in the complex environment of the goaf, this study independently developed an enhanced armored distributed optical fiber for coal mines through experiments. Aiming at the possible influence of the armoring material on the accuracy of temperature measurement, the temperature of the armored distributed optical fiber was corrected through calibration experiments of the armored optical fiber and the heat transfer simulation study of the enhanced temperature measurement optical fiber, to improve the accuracy of the measurement. Based on COMSOL’s simulation study of the spontaneous combustion temperature field and fiber optic detection in the extraction zone, a method of laying optical fibers in parallel at 15-meter intervals to achieve accurate detection of the fire source location in the extraction zone. To explore the feasibility of this technology, a field test was carried out in the 22,117 working faces of Shanxi Lu’an Group Luning Coal Co. Ltd. in the hollow area. The temperature analysis results are consistent with the results of the beam pipe monitoring. The results show that the distributed fiber optic temperature measurement technology can produce a graded warning of spontaneous coal combustion and achieve an accurate detection of the fire source.

Research on the recovery process and product performance of carbon fiber flexible sucker rod in microwave field

As the applications of carbon fiber-reinforced polymers (CFRP) expand, the structures and compositions of the functional products formed from them become more complicated, reducing the effectiveness of conventional pyrolysis in recovering carbon fibers. This research presented the recovery of carbon fiber flexible sucker rods (CFSR) by microwave pyrolysis, and the warming principle of CFSR in a microwave reactor is revealed by a dielectric test system and fiber-optic fluorescence temperature measurement technique. Utilizing a variety of characterization techniques, the structural and mechanical characteristics of the regenerated carbon fibers (RCF) were also assessed, and the influence of heat treatment temperature and duration on the RCF was fully examined. The results demonstrated that the regenerated carbon fibers (RCF) performed best when the heat treatment temperature was set to 550 °C, the reaction time was set to 20 min, and the RCF's outer layer was clean and flat. When compared to virgin carbon fibers (VCF), the RCF's tensile strength and tensile modulus reached 80 % and 91 %, respectively. Furthermore, the composition and structure of the liquid and solid byproducts of CFSR was examined. It was discovered that the liquids contained the highest proportion of hydrocarbons, including methylcyclohexene, and that the solid byproducts also contained cleaner inner glass fibers.

Propagation constant-based diameter measurement technique for a submicrometer-scale optical fiber.

Diameter is a critical parameter for determining the physical properties of a submicrometer optical fiber and requires an accurate measurement. In this study, we proposed, to our knowledge, a novel diameter measurement technique derived from the waveguide theory, utilizing the pitch of a standing-wave near-field light generated by two counter-propagating lights within the submicrometer optical fiber. In a submicrometer optical fiber, the propagating light extends into the surrounding air as near-field light, existing within a range approximately equivalent to one wavelength from the surface of the fiber. By generating the standing-wave near-field light with the incident lights from both ends of the fiber, the pitch of the standing-wave near-field light can be measured by scanning along the fiber's central axis with a scanning near-field optical microscopy probe. The fiber diameter is subsequently acquired by solving the optical fiber eigenvalue equation. Based on the feasibility verification experiment, a high-precision measurement of approximately 0.50 µm was realized for the diameter of the optical fiber.

Dynamic monitoring of a masonry arch rail bridge using a distributed fiber optic sensing system

AbstractMasonry arch bridges are an integral part of the European transportation infrastructure. Regular inspections are critical to ensure the safe operation of these bridges and also to preserve historical heritage. Despite recent advancements in assessment techniques, monitoring masonry arch bridges remains a difficult and important research topic. This paper describes a proof-of-concept study carried out on a masonry arch rail bridge in Gavirate, Italy, to investigate the dynamic responses of the bridge to train-induced moving loads. The dynamic measurements are obtained by a distributed fiber optic sensing system that enables a novel inspection of the integrity of masonry arch bridges. The focus of this field study is to quantify the dynamic strain induced by train moving loads and reveal the masonry arch bridge’s dynamic behaviors through the use of an innovative distributed fiber optical sensing-based technique. The results may provide a useful guideline for the application of distributed fiber optical sensing to monitoring masonry arch bridges.

Enabling long-term distributed OFDR monitoring by exploiting the persistency of the Rayleigh signature

Rayleigh-based distributed fiber optic sensing offers unmatched spatial resolution and accuracy among the different fiber optic techniques. With its sub-centimeter spatial resolution and microstrain accuracy over tens of meters, this technology is ideal for precise monitoring in geotechnical and civil engineering applications.This technique utilizes Rayleigh scattering to track environmental effects on light propagation, and the measurement is done through the spectral correlation analysis of the so-called Rayleigh signature, which is specific to each fiber and can be accounted for to track variation in the light propagation due to the environment. A first measurement of the Rayleigh signature is kept at the beginning of the monitoring campaign, and it is then used as a reference to determine the change in the strain or temperature field affecting the fiber. Still, measurements in installations where fibers were employed in harsh conditions have been shown only in quite favorable conditions, i.e., by using the same specific device and set up over a short time.In this work, we investigate the enduring presence of Rayleigh’s signature in optical sensing fibers installed in challenging environments. In one site, the fibers were cast in the concrete of a bridge foundation pile, subject to an unremitting contraction over the years; in another site, the fibers were integrated within soil anchors subject to the action of an active landslide, which has imparted thousands of strain with marked localized strain peaks. Our study demonstrates that measurements obtained from optical fibers used in adverse conditions continue to exhibit a Rayleigh signature correlating to the reference one, even after a period exceeding five years since the initial measurements were taken and using different interrogators and setups.

The Challenges and Advantages of Distributed Fiber Optic Strain Monitoring in and on the Cementitious Matrix of Concrete Beams

Distributed fiber optic strain measurement techniques have become increasingly important in recent years, especially in the field of structural health monitoring of reinforced concrete structures. Numerous publications show the various monitoring possibilities from bridges to special heavy structures. The present study is intended to demonstrate the possibilities, but also the challenges, of distributed fiber optic strain measurement in reinforced concrete structures. For this purpose, concrete beams for 3-point bending tests were equipped with optical fibers on the reinforcement and concrete surface as well as in the concrete matrix in order to record the strains in the compression and tension zone. In parallel, an analytical approach based on the maximum strains in the uncracked and cracked states was performed using the Eurocode 2 interpolation coefficient. In principle, the structural design correlates with the measured values, but the strains are underestimated, especially in the cracked zone. During load increase, structural distortions in the compression zone affected the strain signal, making reliable evaluation in this zone difficult. The information content of distributed fiber optic strain measurement in reinforced concrete structures can offer tremendous opportunities. Future research should consider all aspects of the bond, sensor selection and positioning. In addition, there is a lack of information on the long-term stability of the joint and the fiber coating, as well as the effects of dynamic loading.

Are Combined Techniques using Video Laryngoscopes and Dynamic Stylets Superior to Fiberoptic Techniques for Anticipating Difficult Intubations? A Retrospective Single-center Comparative Analysis

Introduction: Studies point to the potential advantages of a combined technique using video laryngoscopes (VL) and dynamic stylets for difficult intubations. This study compares the outcomes of three advanced intubation techniques: combined technique (video laryngoscope + dynamic stylet), awake fiberoptic bronchoscope (FOB), and asleep FOB when used as the primary intubation technique. Methods: Airway notes of 138,387 consecutive anesthesia cases at a single academic medical center were filtered for the use of awake FOB, asleep FOB, or combined technique as the primary approach for potentially difficult intubations. The combined technique was defined as VL + dynamic stylet. The dynamic stylets available were FOB or TCITM (Total Control Introducer). The primary endpoint was the first pass success rate. Secondary endpoints included: failure to intubate with the primary technique, anesthesia “in room to intubation” time, “traumatic” intubation rate, and ease of intubation. Results: The first pass success rate was highest for combined techniques (88.7%) followed by awake FOB (74.2%, P<0.001) and asleep FOB (80.7%, P=0.06). “Failure to intubate” was lowest in the combined technique (1.8%), compared to awake FOB (9.2%, P=0.002). “In room to intubation” time was fastest for the combined techniques (13.0 minutes) followed by asleep FOB (15.1 minutes, P=0.002) and awake FOB (21.2 minutes, P<0.001). Combined techniques were recorded as “easy” significantly more often (72%) than awake FOB (38.2%, P<0.001). Combined techniques were recorded as “atraumatic” significantly more often (91.1%) than awake FOB (75.8%, P<0.001). Subgroup analysis of the combined techniques, VL + FOB vs. VL + TCITM, revealed that VL + TCITM was rated as “easy” and “atraumatic” significantly more often. It also achieved higher first pass success, lower “failure to intubate” rate, and faster “in room to intubated” time when compared with VL + FOB, although none reached significance. Conclusion: In this retrospective single-center comparative analysis, the combined techniques outperformed FOB techniques in effectiveness, speed, ease of use, and trauma.

Experimental investigation of the behaviour of pile foundations of a high-rise building

In any high-rise building construction based on piles, it is essential to correctly evaluate their response when subject to high loads to avoid oversizing and consequently high costs. This work falls within the framework of the FONDASILEX project, which studies the behaviour of the pile foundations and the soil within the ‘Silex2’ tower project built in the Part-Dieu district in Lyon, France. This paper presents the geotechnical instrumentation executed for the foundations and the soil to enable the real-time monitoring of their behaviour. It details its conception, execution and limits. Five different types of electrical and unconventional sensors, including the fibre optic technique, which is based on reflectometry by Rayleigh scattering, were employed. This instrumentation allowed us to measure the soil settlement, the applied load at the head of the pile and the induced deformation in the concrete. The obtained measurements showed good agreement between all the sensors and were compatible with the real applied load. The results of this monitoring completed with an additional specific study to characterize the soil will be used in a future study to calibrate numerical models simulating the behaviour of high-rise building foundations.

Experimental validation of DFOS monitoring system for a bridge girder made of wind turbine blade

AbstractThe relatively new fibre optic measurement technique: distributed fibre optic sensing (DFOS) is provided to control strains and displacements, used in the structural health monitoring of a decommissioned wind turbine blade (WTB) bridge girder. The DFOS system is characterized by the following features: accurate, reliable and continuous strain measurements, possibility of assessing shape and displacements, detection of local damages, high durability. Exemplary results of DFOS measurements performed under laboratory conditions on the full‐scale WTB bridge girder are presented. The paper describes the concept of the WTB bridge girder with integrated DFOS monitoring system to control the girder's behavior under loading. Exemplary data of DFOS efficiency were presented and the overall accuracy and reliability of the DFOS measurement system were revealed.

Development of a multi-needle fiberoptic Raman spectroscopy technique for simultaneous multi-site deep tissue Raman measurements in the brain.

We report on the development of a multi-needle fiberoptic Raman spectroscopy (MNF-RS) technique for simultaneous multi-site deep Raman measurements in brain tissue. The multi-needle fiberoptic Raman probe is designed and fabricated using a number of 100 µm core diameter, aluminum-coated fibers under a coaxial laser excitation and Raman collection scheme, enabling simultaneous collection of deep tissue Raman spectra from a number of tissue sites. We have also developed a Raman retrieval algorithm based on the transformation matrix of each individual needle fiber probe projected to different pixels of a charge-coupled device (CCD) for recovering the tissue Raman spectra collected by each needle fiber probe, allowing simultaneous multi-channel detection by a single Raman spectrometer. High-quality tissue Raman spectra of different tissue types (e.g., muscle, fat, gray matter, and white matter in porcine brain) can be acquired in both the fingerprint (900-1800 cm-1) and high-wavenumber (2800-3300 cm-1) regions within sub-second times using the MNF-RS technique. We also demonstrate that by advancing the multi-needle fiberoptic Raman probe into deep porcine brain, tissue Raman spectra can be acquired simultaneously from different brain regions (e.g., cortex, thalamus, midbrain, and cerebellum). The significant biochemical differences across different brain tissues can also be distinguished, suggesting the promising potential of the MNF-RS technique for label-free neuroscience study at the molecular level.

Fiber Bragg grating-based optical filters for high-resolution sensing: A comprehensive analysis

In-fiber Bragg grating filters continue to proliferate, and their applications expand with the rapid advancement of fiber optic component fabrication techniques. Mathematical models for the realisation, characterization, and simulation of fiber Bragg gratings (FBGs) are required to design gratings for various purposes. In this article, a review of the various methodologies is provided. The principles of FBG and the development of FBG-based sensors for temperature, pressure, liquid level, strain, and refractive index sensing in diverse applications have been discussed. The operating concept and performance of cavity structures based on FBG have been investigated. Different sensing architectures with high sensitivity and resolution are presented, including FBG encased in a ring configuration. The basic interrogation techniques are also discussed.

Experimental study on the startup of the annular wick type heat pipe using fiber optical temperature measurement technique

This study used optical fiber-distributed temperature sensors to measure the internal and external temperature distributions of a water-cooled heat pipe. The sensor technology used in this study is fiber optical distributed temperature sensing, a distributed sensing technique based on the naturally occurring Rayleigh backscatter in optical fibers. This measurement technique provides maximum spatial resolution for static and semi-static applications. Using this sensor, the temperature distribution of the heat pipe's internal, external, vapor core, and the wick was measured with a spatial resolution of 0.65 mm, a sampling frequency of 40 Hz, and a temperature resolution of 0.1 °C. Through the measured temperature distribution database, the starting phenomenon, the effective length trend, and the limitation onset were observed. From the results, it is found that a high-temperature peak appears at the evaporator if a high initial power (75 W) is imposed on the heat pipe, even after the heat pipe approaches the normal operating status. The peak is not observed in a slower startup (30 W initial power then slowly increased to 75 W). It is also found that the temperature distributions and effective condenser length of the heat pipe highly depend on the cooling conditions. There are variations in the temperature according to the radial direction of the horizontal heat pipe due to gravity. Lead and lag of the temperature evolution were observed at the onset of the operating limitations.

Fiber Optic based Localized SPR for Nutrients Detection in Modern Agricultural Applications

Detection of nutrients in the hydroponics system, particularly nitrogen, phosphorus, and potassium (NPK) are critical to ensure the good production of crops. Currently, nutrients are analyzed using spectroscopy and electrochemical techniques, which are tedious and sophisticated. This study was conducted to develop a localized surface plasmon resonance (LSPR) fiber optic sensor technique to measure how much content of these nutrients should be added in the soil to increase crop fertility. The main objectives of this study are to study the LSPR fiber sensor technology on NPK in hydroponic systems, to create a fiber optic sensor technique for measuring NPK in hydroponic systems, and finally to characterize the performance of fiber optic sensors for measuring NPK in hydroponic systems. The utilization of the sensing materials, chitosan in this work is to improve the sensitivity feature of the sensor. Chitosan is coated on the surface of the tapered optical fiber prior to the LSPR NPK detection. The results of the absorption spectra will be visible at the end of the experiment where the obtained data are analyzed using SpectraSuite software. The results show that a good linearity was obtained when used AgNP/chitosan as the sensing material with the sensitivity of 0.041 nm ppm-1 in comparison to that of AgNP with the sensitivity of 0.039 nm ppm-1. A better limit of detection (LOD) and limit of quantification (LOQ) was also observed for AgNP/chitosan which are 35.61 ppm and 107.91 ppm, respectively. Meanwhile, AgNP exhibits LOD and LOQ of 106.16 ppm and 494.43 ppm, respectively. It is expected that this work will be a good contributor to the United Nations Sustainable Development Goals (UN SDG), No. 2: Zero Hunger.