Optical Fiber Research Articles

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.

Time Transfer through Optical Fiber and the Effect of Temperature

Time Transfer through Optical Fiber and the Effect of Temperature

Soliton solutions and sensitive analysis to nonlinear wave model arising in optics

In this study, we use analytical algorithms, specifically the auxiliary equation (AE) approach, the improved F-expansion method, and the modified Sardar sub-equation (MSSE) method to investigate complex wave structures for plentiful solutions associated with the fractional perturbed Gerdjikov-Ivanov (PGI) model with the M-fractional operator. The investigated model is a well-established mathematical model used to represent a variety of physical events in nonlinear dynamics and mathematical physics. By using the aforementioned techniques, we scrutinize some new optical wave solutions in the framework of dark, bright, periodic, combo, W-shaped, M-shape, V-shape, kink type, singular rational, exponential, trigonometric, and hyperbolic solutions. The acquired solutions address a wide range of optical solutions in the form of 3D plots, contour plots, and 2D plots, declaring the free parameters of such optical soliton solutions and comprehending their dynamic behavior. Also, the sensitive analysis of the selected model is analyzed. The main contribution of this study is to extract diverse solitary wave solutions of the adopted model. Some of the solutions are similar and some diverge from the previous solutions which justifies the novelty of the study. Finally, we discovered that the current technique provides a reliable instrument for investigating the analytic solutions of fractional differential equations. The proposed PGI model can be used to transmit ultra-fast pulses across optical fibers. This research goes beyond to the advancement of mathematical techniques for solving fractional differential equations and broadens their application to a wide range of real-world scientific and engineering problems.

Plasmonic Optical Fiber Sensors and Molecularly Imprinted Polymers for Glyphosate Detection at an Ultra-Wide Range

Plasmonic Optical Fiber Sensors and Molecularly Imprinted Polymers for Glyphosate Detection at an Ultra-Wide Range

Design of Hollow-core Anti-resonant Optical Fiber Based on Bragg Elements with Low-Loss and Wide Bandwidth

Design of Hollow-core Anti-resonant Optical Fiber Based on Bragg Elements with Low-Loss and Wide Bandwidth

Optical fiber sensor based on magneto-optical surface plasmon resonance with ultra-high figure of merit

Abstract Compared to surface plasmon resonance (SPR), the sensors based on the magneto-optical SPR (MOSPR) technique have much higher figure-of-merit (FOM). However, there are no reports about applying MOSPR in the optical fiber structure now. In this work, a novel D-shaped optical fiber sensor based on the MOSPR technique is proposed. The D-shaped optical fiber is coated with a thin silver film and a magneto-optical (MO) material film of Cerium-doped Yttrium-Iron garnet (CeYIG). By applying a magnetic field on the sensing region, the magneto-optical Kerr effect (MOKE) of the CeYIG layer and the related MOSPR phenomenon could be excited when appropriate light is transmitted in the proposed optical fiber sensor. The influence of the structural parameters including the residual cladding thickness, silver and MO material film thicknesses are analyzed theoretically by the finite element method (FEM). With the optimal parameters, the sensor achieves the sensitivity of 5304 nm/RIU. Since the peak width of MOSPR spectra is much narrower than that of the SPR spectra, the FOM of the sensor is largely enhanced to 3864 RIU^(-1) on average and 13260 RIU^(-1) in maximum, which surpasses the optical fiber SPR sensors vastly. The miniaturized and simple design of the D-shaped optical fiber MOSPR sensor, coupled with the ultra-high FOM, offers itself great potential in biochemical sensing applications.

Design and analysis of D-shaped fiber optic plasmonic sensors using triangular corrugation of silver: transmittance and field analysis

In this study, the wave optics module of COMSOL Multiphysics is used to simulate a D-shaped optical fibre plasmonic sensor with triangular corrugation structures made of silver. The transmittance and electric field-based performance defining parameters i.e., resonance wavelength (λ r), shift in resonance wavelength (∆λ r), minimum transmittance (Tmin), bandwidth (BW), penetration depth (PD), and propagation length (PL) are examined. The obtained sensitivity of the proposed sensor is 10.2 μm RIU−1. It is seen that the proposed sensor structure increases the sensitivity by 41% with respect to planar Ag and 40.2% with respect to rectangular grating of Ag. Also, the PD increases 36.6% with respect to planar Ag and 30% with respect to rectangular grating Ag.

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.

Azimuthal Modulation Instability, Breathers, and Solitons in Ring-Core Optical Fibers

Azimuthal Modulation Instability, Breathers, and Solitons in Ring-Core Optical Fibers

Delineation of gastrointestinal tumors biopsies using a fluorescence lifetime imaging optical fiber probe.

Autofluorescence spectroscopy has emerged in recent years as a powerful tool to report label-free contrast between normal and diseased tissues, both in vivo and ex-vivo. We report the application of an instrument employing an optical fiber probe and capable of performing real-time autofluorescence lifetime imaging at a macroscopic scale, under bright background conditions. We validate and demonstrate the practicality of this technology to discriminate healthy against neoplastic tissue in freshly excised tumor biopsies. The capability of delineating tumor margins through processing the fluorescence decays in the phasors domain was demonstrated on four different types of cancer, highlighting the broad range of potential clinical applications for the proposed approach. The presented results suggest that our autofluorescence lifetime imaging probe, together with phasor analysis, can offer a real-time tool to observe lifetime contrast on tissues and, thus, is a suitable candidate for improving in situ tissue diagnostics during surgery.

Hybrid Si-Au plasmonic sensor on the end-facet of a dual-core optical fiber enhanced by hotspots: a theoretical study

We propose an efficient hybrid Si-Au sensor on the end-facet of a dual-core single-mode optical fiber. The design incorporates slanted Si grating couplers on the two cores, interconnected by a plasmonic waveguide bearing subwavelength corrugations. The corrugations enhance the surface sensitivity by creating regions of strongly enhanced fields - plasmonic hotspots. Unlike conventional Si waveguide grating couplers, we employ slanted slits for unidirectional coupling/decoupling between TM-polarized core light and surface plasmon polaritons. Our structure results in about 3% core-to-core (TM-to-TM) coupling efficiency, while also providing high bulk and surface sensitivities of about 1000 nm RIU−1 and 1.66 nm nm−1, respectively. The sensor can be interrogated remotely in a transmission arrangement. The sensing medium can be probed by dipping the fiber tip directly therein. Potential applications include remote sensing, brain studies, or in-vivo biosensing.

Secondary silicone-induced glaucoma after vitrectomy for regmatogenic retinal detachment

BACKGROUND: Retinal detachment is a leading cause of impaired vision and blindness, affecting 2–9% of individuals. Research has shown that local immune-inflammatory processes contribute significantly to the development of this condition. Polymethylsiloxane has long been used as a tamponade substance in the treatment of retinal detachment. It is currently utilized in various forms of retinal detachment as well as in the management of complications such as retinal edge folding and vitreous opacity. However, the use of silicone oil in the vitreous cavity can lead to the development of secondary ocular hypertension and glaucoma, with prevalence rates ranging from 2.2% to 64.2% according to studies. AIM: Conduct a comparative analysis of biochemical and morphometric indicators and justify the expediency of conducting immune therapy for patients with secondary silicone-induced glaucoma. METHODS: A prospective study included 22 patients (22 eyes) in the main group and 22 patients in the comparison group (22 eyes). The average age of the patients was 55±5.3 years (46–68 years), with 28 females and 16 males. Patients in the main group received anti-cytokine therapy (aminopropyldithioethylene-diamine sodium and anakinra). The primary endpoint of the study was the assessment of retinal nerve fiber layer thickness and perimetric indices. RESULTS: The results revealed an inverse relationship between cytokine levels and retinal nerve fiber layer thickness in patients who underwent vitrectomy with silicone tamponade. Additionally, a direct relationship was observed between the diameter of emulsified silicone in the anterior chamber and cytokine levels. The impact of mechanical fragmentation of polymethylsiloxane during nystagmus and direct toxic effects on optic nerve fibers requires further investigation. The study also highlighted the need for more accurate methods of selecting anterior chamber fluid for evaluating the effectiveness of immune therapy. Determining the appropriate dosage, duration, and administration method of anti-cytokine drugs also requires further research. Evaluation of ophthalmotonometric indicators, retinal nerve fiber layer thickness, and mean deviation revealed significantly better outcomes in patients receiving anti-cytokine therapy compared to the control group. CONCLUSION: The findings of this study support the use of anti-cytokine therapy to normalize biochemical parameters in the anterior chamber and reduce clinical manifestations of secondary silicone-induced glaucoma.

Transformer oil temperature sensing utilizing bundle plastic optical fiber sensor

A bundle plastic optical fiber (POF) that works based on an intensity modulation technique is experimentally demonstrated to sense the temperature of transformer oil. The sensor was developed using a bundle POF that is located perpendicular to an aluminum reflective film with an airgap cavity between these two elements. The simplicity of the architecture allows the development of an economical optical sensor system. To avoid interference effects by other substances in the oil, the sensor head is encapsulated with a metal protecting tube. The temperature measurement was realized in this study by monitoring the output light intensity in the visible light spectrum. For linearity range from 40 °C to 75 °C, the tested sensor exhibits a sensitivity of 0.0064 °C−1, a linearity coefficient of 0.95 and a resolution of 1.56 °C. These results demonstrate the suitability of the developed sensor for temperature oil monitoring in an electrical power transformer system.

First spectroscopic study of HFRC plasma

An advanced spectral diagnostic system was developed to measure the electron temperature (T e), electron density (N e), and ion temperature (T i) of the Huazhong University of Science and Technology field-reversed configuration plasma. The system consists of an optic fiber spectrometer with a wide spectral band and a 670 mm focal length high throughout Czerny–Turner monochromator equipped with both a 3600 g mm−1 grating and a 2400 g mm−1 grating to measure the line spectrum. Accompanying these components is an electron-multiplying charge-coupled device camera to capture spectral data. The relative intensity of the optical fiber spectrometer was calibrated using a standard luminance source, and the wavelength calibration of the spectrometer was accomplished using a Hg/Ar lamp. This diagnostic setup was configured to measure electron density based on the Stark effect of Hγ (n = 5 → n = 2; 434.04 nm). Doppler broadening of an O III (2s22p(2P0)3p → 2s22p(2P0)3s; 375.988 nm) emission line was measured and analyzed to obtain the ion temperature, and electron temperatures were estimated from the relative strength of Hβ (n = 4 → n = 2; 486.14 nm) (Dβ) and Hγ (Dγ) spectral lines when the electron density was obtained from Stark effect measurements. The initial experimental results indicate that the highest electron temperature of the formation region was approximately 8 eV, the electron density of the colliding-and-merging region was approaching 1020 m−3, and the ion temperature reached about 40 eV.

Theoretical Investigation on the Effective Coupling Optical System between Astigmatic Tapered Diode Laser Beam and Single-Mode Optical Fibers

Theoretical Investigation on the Effective Coupling Optical System between Astigmatic Tapered Diode Laser Beam and Single-Mode Optical Fibers

Experimental system and method of aerobic thermal environment simulation based on laser heating

Considering the superior luminous intensity characteristics of lasers, a thermal simulation platform employing laser-induced heating in an aerobic environment was developed. Achieving a uniformly distributed flat-topped square laser beam output was facilitated through optical fibre bundling techniques, while precise control over laser power output was attained through current modulation. Utilising the aforementioned system, thermal shock simulation experiments were conducted in an aerobic environment, subjecting two types of high-temperature-resistant composites, namely C/C and C/SiC, to temperatures up to 1800 °C. These composites were lightweight, heat-resistant materials designed for hypersonic vehicle applications. The results show that the system and method can be used to simulate high temperatures, rapid temperature increases, and thermal shocks on C/C composite materials, with minimal variation in the coupling coefficient under aerobic conditions. The system and method can also provide key technology support for thermal-force-oxygen coupling testing of high temperature resistant materials.

PUDCN: two-dimensional phase unwrapping with a deformable convolutional network

Two-dimensional phase unwrapping is a fundamental yet vital task in optical imaging and measurement. In this paper, what we believe to be a novel deep learning framework PUDCN is proposed for 2D phase unwrapping. We introduce the deformable convolution technique in the PUDCN and design two deformable convolution-related plugins for dynamic feature extraction. In addition, PUDCN adopts a coarse-to-fine strategy that unwraps the phase in the first stage and then refines the unwrapped phase in the second stage to obtain an accurate result. The experiments show that our PUDCN performs better than the existing state-of-the-art. Furthermore, we apply PUDCN to unwrap the phase of optical fibers in optical interferometry, demonstrating its generalization ability.

Triple-Channel Optical Fiber Surface Plasmon Resonance Sensor for Simultaneous Detection of Relative Humidity, Magnetic Field, and Temperature

Triple-Channel Optical Fiber Surface Plasmon Resonance Sensor for Simultaneous Detection of Relative Humidity, Magnetic Field, and Temperature

Identification of Corrosion-Induced Optical Fiber Acoustic Emission Sensor Signals on the Bottom Plate of Oil Storage Tank Based on Multichannel Attention Mechanism (CBAM)

Identification of Corrosion-Induced Optical Fiber Acoustic Emission Sensor Signals on the Bottom Plate of Oil Storage Tank Based on Multichannel Attention Mechanism (CBAM)

Perspectives on endoscopic functional photoacoustic microscopy.

Endoscopy, enabling high-resolution imaging of deep tissues and internal organs, plays an important role in basic research and clinical practice. Recent advances in photoacoustic microscopy (PAM), demonstrating excellent capabilities in high-resolution functional imaging, have sparked significant interest in its integration into the field of endoscopy. However, there are challenges in achieving functional PAM in the endoscopic setting. This Perspective article discusses current progress in the development of endoscopic PAM and the challenges related to functional measurements. Then, it points out potential directions to advance endoscopic PAM for functional imaging by leveraging fiber optics, microfabrication, optical engineering, and computational approaches. Finally, it highlights emerging opportunities for functional endoscopic PAM in basic and translational biomedicine.