About
524
Publications
91,814
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
9,017
Citations
Introduction
Additional affiliations
September 2013 - present
September 2012 - present
January 2002 - December 2012
Education
January 2006 - December 2009
Publications
Publications (524)
The aim of this work is to introduce a novel digital signal processing method for data acquired using Low Coherence Interferometry (LCI) with a 1 kHz actuator oscillation frequency. Convolution and correlation operations are employed as efficient filters, reducing computational complexity for multi-layer filtering. An envelope filtering technique i...
Azobenzenes are a class of compounds presenting photoisomerization capabilities that allow the writing and erasure of birefringence along a desired direction. This feature enables applications requiring polarization control, which although have been extensively investigated in the visible light spectrum, poor emphasis has been paid to the infrared...
Distributed acoustic sensing (DAS) is a sensing technique that allows continuous data acquisition of strain rate and temperature with exceptional spatial resolution, up to few meters, for extensive lengths up to 100 km. The ubiquitous nature of optical fiber cables rendered DAS an appealing alternative for geophysical sensing, allowing cost-effecti...
This work proposes a signal processing algorithm to analyse the optical signal from a Low Coherence Interferometric (LCI) system. The system uses a Mach-Zehnder (MZ) interferometer to interrogate a Fabry-Perot cavity, working as an optical sensor. This algorithm is based on the correlation and convolution operations, which allows the signal to be r...
Raman technology offers a cutting-edge approach to measuring glucose solutions, providing precise and non-invasive analysis. By probing the vibrational energy levels of molecular bonds, Raman technology generates a unique spectral fingerprint that allows for the accurate determination of glucose concentrations. This study proposes the use of Raman...
Optical fiber sensors were implemented to measure in-situ temperature variations in an oscillatory flow crystallizer operating in continuous. The sensors were fabricated by cleaved in the middle 8 mm-length fiber Bragg gratings, forming tips with a Bragg grating of 4 mm inscribed at the fiber ends. The geometry of the sensors fabricated, with a dia...
This paper presents a new type of phase-shifted Fiber Bragg Grating (FBG): the sliced-FBG (SFBG). The fabrication process involves cutting a standard FBG inside its grating region. As a result, the last grating pitch is shorter than the others. The optical output signal consists of the overlap between the FBG reflection and the reflection at the fi...
This study investigated the effectiveness of a coil-shaped optical fiber interferometric sensor, with a diameter of 13 mm, for measuring compression. The sensor’s design utilizes the principles of interferometry to create a pattern that changes with applied pressure. This configuration significantly amplifies the sensor’s sensitivity to compression...
Frazao This paper introduces an innovative two-core fiber (TCF) optic sensor employing a Mach-Zehnder interferometer (MZI) to monitor the optogenetic response of light-sensitive human dental pulp stem cells (hDPSCs). The in-fiber MZI, formed using a segment of TCF optic, detects refractive index (RI) changes in the surrounding medium. The sensor ut...
In this study, different configurations based on linear fiber lasers were proposed and experimentally demonstrated to measure the concentration of liquid solutions. Samples of paracetamol liquid solutions with different concentrations, in the range from 52.61 to 201.33 g/kg, were used as a case-study. The optical gain was provided by a commercial b...
This work addresses the historical development of techniques and methodologies oriented to the measurement of the internal diameter of transparent tubes since the original contributions of Anderson and Barr published in 1923 in the first issue of Measurement Science and Technology. The progresses on this field are summarized and highlighted the eme...
In this study, different configurations based on linear fiber lasers were proposed and experimentally demonstrated to measure the concentration of paracetamol liquid solutions in a range of 52.61 to 201.33 g/kg. The optical gain was provided by a commercial bidirectional Erbium-Doped Fiber Amplifier (EDFA) and the linear cavity was obtained using t...
This paper presents an approach to enhancing sensitivity in optical sensors by integrating self-image theory and graphene oxide coating. The sensor is specifically engineered to quantitatively assess glucose concentrations in aqueous solutions that simulate the spectrum of glucose levels typically encountered in human saliva. Prior to sensor fabric...
White Light Interferometry, known for its absolute measurement capability and high precision, had its greatest scientific impact towards the end of the 20th century. In this work, it was assembled and characterized a fibre Mach-Zehnder interferometer (MZI) as an interrogator and a fibre Fabry-Perot interferometer (FPI) as a displacement sensor. A m...
This paper proposes a proof of concept for a reflective fiber optic sensor based on multimode interference, designed to measure glucose concentrations in aqueous solutions that mimic the range of glucose concentrations found in human saliva. The sensor is fabricated by splicing a short section of coreless silica fiber into a standard single-mode fi...
In this work, an optical fiber flowmeter based on a Michelson interferometer is presented. The Michelson interferometer uses a long period fiber grating (LPFG) to couple light to the cladding modes followed by a section of a GO-coated single mode fiber (SMF). By radiating the GO thin film, it will increase its temperature changing the effective ref...
The scientific community has been exploring new concepts as a result of the usage of optical fibers as absolute measurement sensors. While cross-sensitivity is a common issue with optical fiber sensors, this issue has been mitigated by simultaneous measurement techniques. But when it comes to absolute measurements, these methods have some limitatio...
This work proposes a sensor that utilizes a transmission scheme for measuring glucose aqueous solutions based on surface plasmon resonance. A comparison between the performance of two sensors with similar lengths and different diameters is performed. The first sensor comprises a multimode optical fiber with a diameter of 400 µm and a 10 mm middle s...
This work presents an interrogator system based on an erbium-doped fiber ring cavity for refractive-index measurements. This fiber ring cavity is assisted by a fiber Bragg grating and a phase-shift fiber Bragg grating, both with a similar central emission wavelength to increase the output power levels.
The refractometric analysis of ethanol-water mixtures is hampered because this type of binary solution does not present a linear behaviour. In this work it is proposed a multimode Graded-Index Fiber (GIF) tip sensor for the measurement of ethanol in binary liquid solutions of ethanol-water. The probe is fabricated by fusion-splicing a 500 µm GIF to...
The refractometric analysis of ethanol-water mixtures is hampered because this type of binary solution does not present a linear behavior. In this work it is proposed a multimode Graded-Index Fiber (GIF) tip sensor for the measurement of ethanol in binary liquid solutions of ethanol-water. The prove is fabricated by the fusion-splicing of a 500 μm...
Systems for wireless energy transmission (WET) are gaining prominence nowadays. This work presents a WET system based on the photo‐thermoelectric effect. With an incident laser beam at λ = 1450 nm, a temperature gradient is generated in the radial flexible thermoelectric (TE) device, with a carbon‐based light collector in its center to enhance the...
A paracetamol concentration-sensing scheme based on a linear cavity fiber laser configuration is demonstrated
experimentally. The laser cavity has a fiber sensor at one end, that allows refractive index measurements. The
refractometer consists of a cleaved fiber tip combined with an FBG functioning as a reflecting mirror. The
combination of a fiber...
Process Analytical Technology (PAT) has been increasingly used in the pharmaceutical industry to monitor essential parameters in real-time during pharmaceutical processes. The concentration of Active Pharmaceutical Ingredients (APIs), such as paracetamol, is one of these parameters, and controlling its variations allows for optimization of the prod...
This paper has been formally retracted because it has been accidentally published the volume. Request approved by the proceedings Editor and the Publisher on October 24, 2022.
An optical strain gauge based on a balloon-like interferometer structure formed by a bent standard single-mode fiber combined with a 3D printer piece has been presented and demonstrated, which can be used to measure displacement. The interferometer has a simple and compact size, easy fabrication, low cost, and is repeatable. The sensor is based on...
This study presents the dependence of strain sensitivity on cavity length in conventional Fabry–Perot (F‐P) sensors. A high number of F‐P sensors were required and to ensure their reproducibility, a manufacturing process was developed to obtain similar sensors but with different types of lengths. A hollow‐core silica tube was used to fabricate seve...
In many areas, the analysis of a cylindrical structure is necessary, and a form to analyze it is by evaluating the diameter changes. Some areas can be cited: pipelines for oil or gas distribution and radial growth of trees whose diameter changes are directly related to irrigation and the radial expansion since it depends on the water soil deficit....
In this work, a brief review on the application of fiber optic sensors on power grid apparatus is presented. Power transformers, which are the nodes between electrical transmission lines, are the most expensive, critical and one of the central units of this network. The failure of electrical machines compromises the whole grid leading to power outa...
Thin films of titanium dioxide (TiO2) and titanium (Ti) were deposited onto glass and optical fiber supports through DC magnetron sputtering, and their transmission was characterized with regard to their use in optical fiber-based sensors. Deposition parameters such as oxygen partial pressure, working pressure, and sputtering power were optimized t...
Cylindrical structure analysis is important in several areas and can be performed through the evaluation of the diameter changes of these structures. Two important areas can be mentioned: pipelines for oil or gas distribution and the condition and growth of trees. In the tree diameter changes, monitoring is directly related to irrigation, since it...
We propose a fiber-based environmental sensor that exploits the reflection-phase-shift tunability provided by the use of layered coatings composed of dielectric slabs spaced by conducting membranes. A transfer-matrix study is done in a simplified theoretical model, for which an enhanced sensitivity of the reflection interference pattern to the outp...
Power transformers are central elements of power transmission systems and their deterioration can lead to system failures, causing major disruptions in service. Catastrophic failures can occur, posing major environmental hazards due to fires, explosions, or oil spillage. Early fault detection can be accomplished or estimated using electrical sensor...
We propose a novel fiber-based environmental sensor that exploits the reflection phase shift tunability provided by the use of layered coatings composed of dielectric slabs spaced by conducting membranes. A transfer matrix study is done in a simplified theoretical model, for which an enhanced sensitivity of the reflection interference pattern to th...
The optical analog of the Vernier effect applied to fiber interferometers is a recent tool to enhance the sensitivity and resolution of optical fiber sensors. This effect relies on the overlap between the signals of two interferometers with slightly detuned interference frequencies. The Vernier envelope modulation generated at the output spectrum p...
A Fabry–Pérot acoustic sensor based on a graphene oxide membrane was developed with the aim to achieve a faster and simpler fabrication procedure when compared to similar graphene-based acoustic sensors. In addition, the proposed sensor was fabricated using methods that reduce chemical hazards and environmental impacts. The developed sensor, with a...
Thin graphene oxide (GO) film layers are being widely used as sensing layers in different types of electrical and optical sensor devices. GO layers are particularly popular because of their tuned interface reflectivity. The stability of GO layers is fundamental for sensor device reliability, particularly in complex aqueous environments such as wast...
: The development of novel biosensors and other medical devices often implies extensive animal testing before the final
phases of product development are reached. Most products do not reach the market. On the other hand, natural disease in companion
animals often mirrors disease processes in humans, being a more accurate representation of the compl...
A strain gauge sensor based on Fiber Bragg Grating (FBG) for diameter measurement is proposed and experimentally demonstrated. The sensor is easily fabricated inserting the FBG on the strain gauge-it was fabricated using a 3D printer-and fixing the FBG in two points of this structure. The idea is to vary the diameter of the structure. We developed...
A fiber sensor composed by a graphene oxide membrane at the tip of a capillary is presented. The graphene oxide membrane acts as a low-reflectivity mirror, distanced from a single mode fiber forming a low finesse Fabry-Perot interferometer. The response of the sensor to acoustic pressure with varying frequency is studied in the range between 5 and...
We discuss the novel concept of harmonics of the Vernier effect for optical fiber sensors as a tool to break the limits of conventional optical Vernier effect currently used. The new effect provides enhancements scalable with the harmonic order.
The optical Vernier effect consists of overlapping responses of a sensing and a reference interferometer with slightly shifted interferometric frequencies. The beating modulation thus generated presents high magnified sensitivity and resolution compared to the sensing interferometer, if the two interferometers are slightly out of tune with each oth...
Microfiber knot resonators are widely applied in many different fields of action, of which an important one is the optical sensing. Microfiber knot resonators can easily be used to sense the external medium. The large evanescent field of light increase the interaction of light with the surrounding medium, tuning the resonance conditions of the stru...
A silica resonator was demonstrated for random laser generation. The resonator consisted of a conventional microsphere fabricated in an optical fiber tip through electric arc discharge, and modifications to its geometry were carried out to create asymmetry inside the silica structure. The resulting Bunimovich stadium-like microsphere promotes multi...
A brief review of new fiber microsphere geometries is presented. Simple microspheres working as Fabry-Perot cavities are interrogated in reflection and in transmission. Two microspheres were also spliced together, and subjected to different physical parameters. These structures are an alternative solution for load measurement and, when read in tran...
A multi-path interferometer based on a polished multimode microsphere is proposed for temperature sensing. Asymmetry was introduced in the structure by polishing the microsphere with a certain angle. A new set of optical paths are generated in the polished microsphere due to the different reflections inside of the structure. The interference betwee...
A sensing structure based on a cleaved silica microsphere is proposed for temperature sensing. The microsphere was cleaved using focused ion beam milling. The asymmetry in the structure introduced by the cut generates not only new cavities but also random interferometric reflections inside the microsphere. These two spectral components can be separ...
The purpose of the present work is to construct a reaction board based on fiber Bragg gratings (FBGs) that could be used for estimation of the 2D coordinates of the projection of center of gravity (CG) of an object. The apparatus is consisted of a rigid equilateral triangular board mounted on three supports at the vertices, two of which have cantil...
In this work, an alternative method of coupling light into microstructured polymer fibers is presented. The solution consists in using a fiber taper fabricated with a CO2 laser. The connection is formed by inserting a tapered silica tip into the holes of a microstructured polymer fiber. This alternative method is duly characterized and the feasibil...
This paper presents a simplification design for the fiber cavity ring-down technique. The new configuration is no longer in ring cavity and is converted to a linear cavity. The proposed linear cavity is created with a single fibre coupler of 99:1 and two thin-film mirrors located at the end of the fibre arms. This configuration can be interrogated...
The use of a polymer fiber as a refractive index sensor is proposed. A fiber Bragg grating is inscribed near the fiber tip and the fiber is cut shorter thus creating a Fabry-Perot cavity. The reflections between the fiber Bragg grating and the fiber end-face create a Fabry-Perot interferometer. The sensor was characterized to refractive index chang...
This work reports a multimode interference-based fiber sensor in a cavity ring-down system (CRD) for sensing temperature-induced refractive index (RI) changes of water. The sensing head is based in multimodal interference (MMI) and it is placed inside the fiber loop cavity of the CRD system. A modulated laser source was used to send pulses down int...
Two different sensing structures based on a hollow microsphere Fabry-Perot cavity are proposed. The hollow spheroidal cavities are fabricated resorting only to fusion splicing. The first structure is based on a hollow microsphere located at the fiber end and works as a probe sensor. The structure was subjected to lateral load pressure and presents...
A Mach-Zehnder interferometer was created from a cavity milled in the taper region next to a microfiber knot resonator. A focused ion beam was used to mill the cavity with 47.8 μm in length. The microfiber knot resonator was created from an 11 μm diameter taper, produced using a filament fusion splicer. After milling the cavity, the microfiber knot...
Microfiber knot resonators find application in many different fields of action, of which an important one is the optical sensing. The large evanescent field of light can interact and sense the external medium, tuning the resonance conditions of the structure. The resonant property of microfiber knot resonators can also provide, in some cases, an en...