Elfed Lewis

Elfed Lewis
University of Limerick | UL · Department of Electronic and Computer Engineering

PhD

About

482
Publications
132,732
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4,948
Citations

Publications

Publications (482)
Article
Full-text available
A femtosecond (fs) laser fabricated refractive index (RI) modulated multimode fiber (MMF) for high sensitivity vector bending measurement is presented. A fs laser-induced local positive RI modulation in the MMF core results in a non-circular symmetric RI distribution of the MMF. Such a RI-modulated MMF used in single-mode-multimode-single-mode (SMS...
Article
Full-text available
In this article, a novel long-period fiber grating (LPFG) sensor based on a core-cladding misalignment structure is described. The LPFG consists of multiple short-length singlemode fiber (SMF) segments joined with core-cladding misalignment splicing. Due to the refractive index (RI) difference between the core and the cladding, periodic RI modulati...
Article
The spectral characteristics of the relative intensity noise (RIN) of two amplified spontaneous emission (ASE) sources are experimentally measured. An Er-doped fiber superfluorescent source (EDF-SFS) is investigated and compared with a super-luminescent diode (SLD) source, using a simple tunable fiber Bragg grating filter-based system. Experimental...
Article
Full-text available
The torsion measurement and torsion direction discrimination characteristics of a multimode fiber (MMF) geometry in a singlemode-multimode-singlemode (SMS) fiber structure are investigated theoretically and experimentally. Three different geometries of MMFs, including circular symmetric MMF, axisymmetric MMF, and asymmetric MMF were fabricated base...
Article
Full-text available
A range of optical fibre-based sensors for the measurement of ethanol, primarily in aqueous solution, have been developed and are reviewed here. The sensing approaches can be classified into four groups according to the measurement techniques used, namely absorption (or absorbance), external interferometric, internal fibre grating and plasmonic sen...
Article
Full-text available
This Special Issue captures a significant portion of the current sensors research excellence in Ireland [...]
Article
Measurements using an Optical Fiber OFS including an inorganic scintillator placed on the surface of a phantom show that the particle energy distribution inside the phantom remains unchanged. The backscattered intensity measured using an Optical Fiber Sensor (OFS) exhibits a linear relationship with the total radiation dose delivered to the phantom...
Article
A novel all-optical modulator based on a microfibre coil resonator (MCR) functionalized using MXene is reported. The MCR was manufactured by winding a tapered fibre on a polycarbonate (PC) resin cylinder with low refractive index to support the microfibre, which also forms a fluidic channel coil. The MXene dispersion was injected into the channel t...
Article
Full-text available
The use of optical fiber probe in two-phase flow measurements is very frequently encountered, especially in the applications of chemical engineering and petroleum industries. In this work, the influence of bubble piercing signals caused by bubble deformation is studied experimentally using a laboratory-prepared wedge-shaped fiber probe in a lab-sca...
Presentation
A Light Talk on Industry 4.0 Prospects of Optical Fibre Sensing for Biofuel Processing Industry.
Article
Full-text available
An ultra-compact in-core-parallel-written fiber Bragg grating (FBG) and Mach-Zehnder interferometer (MZI) for simultaneous measurement of strain and temperature is described. The FBG and MZI are written spatially parallel in the same section of fiber core using a femtosecond laser, forming an ultra-compact device, which is different from the previo...
Article
Full-text available
Background: Cesium-137 is one of those man-made radioactive nuclides that results from human activities including open air nuclear weapons testing, nuclear accidents, operation of nuclear reactors and has a relative long halflife, higher water solubility, high fission yield, relatively high volatility and a close physic-chemical similarity to potas...
Presentation
A U-bend POF Sensor is a potential solution for real-time monitoring of the production of biofuels, such as bioethanol even at the very low-level initial concentration of product which can occur during the initial production stage via recombinant Cyanobacteria strains such as Synechocystis PCC6803. The sensor demonstrates excellent repeatability an...
Article
A conical tip-shaped plastic optical fiber sensor for gas-liquid flow measurement is described. Experimental results show that a distinctive spike signal occurs before the output signal when using a conventional conical fiber probe, whereas this spike signal was greatly suppressed when a cleaved probe is used. A full simulation is implemented based...
Article
Fiber optic sensors have contributed a huge market for sensing some quantity, typically temperature or mechanical strain, and even for displacements, vibrations, pressure, acceleration, rotations, or concentrations of chemical species. The application in defense and engineering remains the largest market for fiber optic sensors (FOSs). The success...
Article
A algorithm of obtaining absolute dose at each tissue depth only by the mathematical calculation of formula is reported. The algorithm is based on integrating the energy flux of the electron generated by X-ray in the range of irradiation field, and the energy spectrum of ray and the secondary scattered ray are considered in this process. In this al...
Article
The purpose of this article is to explore the cause of the over-response phenomenon of fiber x-ray sensor. The sensor is based on a length of PMMA fiber, whose end is filled with the scintillation material Gd 2 O 2 S:Tb. The Monte Carlo simulation software GEANT4 uses the phase space file provided by the International Atomic Energy Agency (IAEA), b...
Article
Nickel disulfide (NiS2) has recently been found to possess strong nonlinear saturable absorption properties. This feature is highly attractive for nonlinear photonics applications. Ultrafast pulse generation is successfully demonstrated in this article for both Ytterbium- and Erbium-doped fibre lasers using micro-fibre deposited nickel disulfide (N...
Article
Full-text available
This article explains about the development of an optical sensor system to detect and measure ammonia emission in the agricultural field. At initial stage, an open path optical technique where a cylindrical chamber is used to detect low concentration of ammonia in the UV region. The methodology describing the working principle of the sensor and the...
Article
The use of optical fiber X-ray sensors is of great significance in X-ray detection. To reduce the influence of background noise attributed to sources such as Cerenkov radiation, the response of a plain (no scintillator material added) optical fiber to the X-ray radiation is investigated. The percentage dose-depth (PDD) of plain optical fibers with...
Article
Full-text available
The release of natural radioactive materials with the emission of fly ash as a result of coal burning in power generation plants is considered amongst the sources that elevate the technologically environmental radioactivity level. This research mainly concerns the assessment of various radiological parameters including excess lifetime cancer risk d...
Article
A laboratory-prepared wedge-shaped fiber probe using step-index multimode plastic optical fiber was described and tested in a lab-scale gas-liquid flow generator. A three-dimensional model was established in order to fully simulate the process of bubble piercing by the optical fiber probe. A theoretical analysis of the luminous intensity distributi...
Article
Intense mid-infrared emission at 3.9 µm in Ho3+-doped ZBYA glasses with direct upper laser level (Ho3+:5I5) pumping at a wavelength of 888 nm is reported for the first time, to the best of our knowledge. Spectroscopic parameters were determined using the Judd-Ofelt theory and the measured absorption spectrum. The maximum emission cross section of t...
Article
A low-cost optical fibre sensor based on two cascaded balloon-like bent fibre (BBF) structures for simultaneous displacement and temperature measurement is reported. The sensor is fabricated by cascading two balloon-like bent single-mode fibres (SMFs) which with different bending radii, generating two separate interference dips within a limited wav...
Article
A reliable, accurate and in-vivo dosimetry system for measuring the radiation dose and profiling the X-ray beam during radiotherapy is reported. Its dynamic range is investigated using an accurately controlled pulsed light emitting diode (LED) system. Highly resolved temporal analog and digital signals were captured from the analog and digital outp...
Article
This article presents for the first time an ultrasensitive localized surface plasmon resonance (LSPR) sensor system based on multimode-singlemode-multimode fiber (MMF-SMF-MMF) structure for the accurate measurement of copper (II) Ion (Cu²⁺). Citrate-stabilized [email protected] core-shell nanospheres (NSs) with a rough AgPt alloy outer shell were s...
Article
In this article, a high sensitivity, low temperature-crosstalk strain sensor based on a microsphere embedded Fabry-Perot interferometer (FPI) is reported and experimentally demonstrated. The sensor is fabricated by embedding a microsphere inside a tapered hollow-core fiber (HCF) whose ends are enclosed by two standard single-mode fibers (SMFs). The...
Conference Paper
Full-text available
A novel Fabry-Perot sensor, comprised a glass sphere bonded to a capillary and singlemode fiber, is proposed for refractive index sensing. It is characterized in air, water, ethanol, isopropanol, and glycerol.
Article
Full-text available
An angled polished multimode (APM) fibre structure is described for the first time, to the best our knowledge, and its polarization dependence investigated theoretically and experimentally. Two angled planes are established in the multimode fibre (MMF) section of a single-mode-multimode-single-mode (SMS) fibre structure using the fibre side-polishi...
Article
Full-text available
Lead germanate glass samples with different Er3+/Yb3+ concentrations co-doped were prepared and the color variation of the up-conversion emissions in these glasses was observed using 980 nm laser pump power. A practical optical integrated device based on Er3+-Yb3+ co-doped lead germanate glass microsphere and a special fiber structure, consisting o...
Article
Full-text available
About 87% of the total dose received by the general public is due to naturally existing radioactive nuclides. Long-term exposure to the relatively long half-life radioactive elements (including Uranium, Thorium, and Potassium) and their decay products pose severe health threats to the population including lung cancer. The related available data has...
Chapter
Full-text available
This chapter provides expert coverage of the physical properties of new noncrystalline solids—tellurite glass and the latest laser applications of the material—offering insights into innovative applications for laser and sensing devices, among others. In particular, there is a focus on specialty optical fibers, supercontinuum generation and laser d...
Article
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A range of new 2D materials have recently been reported, including topological insulators, transition-metal dichalcogenides, black phosphorus, MXenes, and metal-organic frameworks, which have demonstrated high optical nonlinearity and Pauli blocking for widespread use as saturable absorbers in pulsed lasers. 2D materials are emerging as a promising...
Article
Full-text available
Background: The aim & objective of this study is to evaluate the health hazards of the general public from the existence of the radioactive nuclides in the soil of North Waziristan and to establish a reference line for future work on radioactivity concentration in this locality. Methods and Materials: A highly background radiation shielded HPGe sys...
Article
Full-text available
Wheat flour is a dietary staple of Pakistani population. This study is mainly focused on the measurement of radioactivity concentration due to naturally occurring radioactive nuclides, uranium-238, thorium-232, potassium-40, and the corresponding hazardous radiological parameters, radium equivalent dose (Ra eq ), annual effective dose, internal haz...
Article
A single-mode-multimode-single-mode (SMS) optical fiber-based displacement sensing system mounted on an Ilizarov transverse tibial bone transport device for microcirculation reconstruction is reported. Wide-range displacement is approximated as a uniform extension of a spring that is connected to an SMS optical fiber structure acting as the displac...
Article
Full-text available
We propose and demonstrate a miniature Fabry-Perot interferometer (FPI) based on a movable microsphere reflector. The movable microsphere acts as a good reflector, with the reflections occurring at the spliced single-mode fiber/hollow-core fiber interface and the surface of a microsphere, resulting in two-beam interference. The silica microsphere i...
Article
Full-text available
A bismuth‐doped compound glass‐based microsphere laser is reported. The fluorescence luminescence of the bismuth‐doped compound glass is measured over an ultra‐broad wavelength range of 1100 to 1700 nm excited using an 808 nm pumping source. The glass microsphere was fabricated using a CO2 laser heating the fiber near its melting temperature, and w...
Article
Full-text available
The power coupling ratio between step-index multimode fibers caused by combined transversal and angular misalignment is calculated. A theoretical description of the coupling efficiency between two optical fibers based on geometrical optics is provided. The theoretical calculations are collaborated by experiments, determining the power coupling rati...
Article
Simultaneous 1.50 μm, 1.84 μm and 2.08 μm laser emission is observed in a Ho³⁺/Tm³⁺ co-doped ZrF4–BaF2–YF3–AlF3 (ZBYA) fluoride glass microsphere when pumped using a 793 nm laser diode. The ZBYA fluoride glass microsphere was prepared using a CO2 laser heating method and whispering-gallery modes (WGM) were excited when the pump light was coupled us...
Article
Type I fiber Bragg grating (FBG) regeneration is studied in terms of refractive index modulation (RIM) and characterized using optical low-coherent reflectometry (OLCR) for the first time. Highly resolved spatial OLCR results are used to demonstrate a uniform RIM regeneration ratio along an apodized type I the FBG during the regeneration process. R...
Article
Full-text available
Up-conversion luminescence and C-band microsphere laser output is reported for an $\text{Er}^{3+}$ -doped $\text{ZrF}_4 \text{-BaF}_2 \text{-YF}_3 \text{-AlF}_3$ (ZBYA) fluorozirconate glass microsphere. The microsphere was fabricated by heating a ZBYA glass filament using a $\text{CO}_2$ laser beam. The fabrication process accurately and rep...
Article
Full-text available
Inorganic scintillating material used in optical fibre sensors (OFS) when used as dosimeters for measuring percentage depth dose (PDD) characteristics have exhibited significant differences when compared to those measured using an ionization chamber (IC), which is the clinical gold standard for quality assurance (QA) assessments. The percentage dif...
Article
A novel fiber-optic refractive index (RI) and temperature sensor based on a multimode-single-mode-multimode fiber (MMF-SMF-MMF) structure coated with graphene-metal hybrid films was proposed and investigated. The surface plasmon resonance (SPR)-based RI sensitivity is improved by the addition of the graphene layer above or below the gold coating of...
Article
Full-text available
Q-switched pulse laser generation is successfully demonstrated in both Erbium-doped fibre laser (EDFL) and Thulium-doped fibre laser (TDFL) cavities by employing Nickel disulfide (NiS2) as a saturable absorber (SA). Q-switched pulse laser operation at 1.55 μm and 2.0 μm is obtained at low pump power levels of 37 mW and 48 mW, respectively. For the...
Article
Directly pumped single-mode and multimode Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped sol-gel silica microspheres lasing at $2.0~\mu \text{m}$ are observed, when an 1150-nm fiber Raman laser pump is used in a conventional microfiber-microsphere coupling method. Experimental res...
Article
Full-text available
A novel, to the best of our knowledge, in-fiber temperature sensor based on green up-conversion (UC) luminescence in an Er3+-Yb3+ co-doped tellurite glass microsphere is described. The tellurite glass microsphere is located firmly inside a suspended tri-core hollow-fiber (STCHF) structure. The pump light launched via a single-mode fiber (SMF) is pa...
Article
A novel robust compact light emitting diode (LED) based laboratory simulator system for mimicking the output from an optical fibre sensor used to detect therapeutic X-ray pulses from a clinical linear accelerator (linac) is described and performance characterised with reference to real clinical data. The purpose of configuring the LED system is to...
Article
Full-text available
The use of tin disulfide (SnS2) as a candidate material for saturable absorption in nonlinear optical devices is investigated in this article. A dual-wavelength soliton mode-locked fiber laser is demonstrated using a fabricated SnS2 thin film as a saturable absorber within an erbium-doped fiber laser cavity. The laser generates two peaks centered a...
Article
Full-text available
A black phosphorus (BP) functionalized optical fiber sensor based on a microfiber coil resonator (MCR) for Pb2+ ion detection in an aquatic environment is presented and experimentally demonstrated. The MCR-BP sensor is manufactured by winding a tapered microfiber on a hollow rod composed of a low-refractive-index polycarbonate (PC) resin with the B...
Article
Full-text available
This edition of Around the World of IoT presents a summary of the IEEE World Forum on Internet of Things (WF-IoT 2019) that was held in April in Limerick, Ireland. Arriving at its fi fth edition, the WF-IoT is the fl agship event organized by the IEEE IoT Initiative, a multi-society activity gathering 20 IEEE member societies/ councils. Due to its...
Article
Radiation dosimetry plays a crucial role in the Quality Assurance (QA) in radiotherapy. To date this is limited to monitoring the overall dose over the complete beam time and so there is limited information on the actual beam quality. An optical fibre sensor is developed based on cerium doped yttrium aluminum garnet (YAG:Ce) scintillator. The tempo...
Article
Full-text available
A regenerated fiber Bragg grating (RFBG) in silica fiber was used to observe the viscous relaxation process of the host silica fiber at high temperatures of around 1000 °C. Two factors, preannealing time and loaded tension, which affect viscous relaxation, were observed. When an RFBG is stretched after a longer preannealing, the measured viscosity...
Article
Full-text available
A temperature-insensitive refractometer based on a refractive index (RI)-modulated singlemode-multimode-singlemode (RMSMS) fibre structure is proposed and experimentally demonstrated. In this investigation, a combination of no-core fibre (NCF) and multimode fibre (MMF) regions provides an RI modulation region due to the difference in RI between the...