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Detalhes

Detalhes

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Publicações

2022

Sputtering Deposition of TiO2 Thin Film Coatings for Fiber Optic Sensors

Autores
Silva, D; Monteiro, CS; Silva, SO; Frazao, O; Pinto, JV; Raposo, M; Ribeiro, PA; Serio, S;

Publicação
PHOTONICS

Abstract
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 to attain films with a high reflectance. The films deposited on glass supports were characterized by UV-Vis spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Regarding the deposition parameters, all three parameters were tested simultaneously, changing the working pressure, the sputtering power, and the oxygen percentage. It was possible to conclude that a lower working pressure and higher applied power lead to films with a higher reflectance. Through the analysis of the as-sputtered thin films using X-ray diffraction, the deposition of both Ti and TiO2 films was confirmed. To study the applicability of TiO2 and Ti in fiber sensing, several thin films were deposited in single mode fibers (SMFs) using the sputtering conditions that revealed the most promising results in the glass supports. The sputtered TiO2 and Ti thin films were used as mirrors to increase the visibility of a low-finesse Fabry–Perot cavity and the possible sensing applications were studied.

2022

Brief Review on Optical Fiber Sensing for the Power Grid

Autores
Rodrigues, AV; Monteiro, C; Silva, SO; Linhares, C; Mendes, H; Tavares, SMO; Frazão, O;

Publicação
U.Porto Journal of Engineering

Abstract
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 outages and income losses. Thus, constant monitoring of structural health and operating conditions of core infrastructures is sought. With different types of sensors either on the market or in the literature, it is possible to measure physical parameters that make this equipment more reliable.

2022

A Simple Optical Sensor Based on Multimodal Interference Superimposed on Additive Manufacturing for Diameter Measurement

Autores
Cardoso, VHR; Caldas, P; Giraldi, MTR; Fernandes, CS; Frazao, O; Costa, JCWA; Santos, JL;

Publicação
SENSORS

Abstract
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. For some species, these radial variations can change in around 5 mm. This paper proposes and experimentally investigates a sensor based on a core diameter mismatch technique for diameter changes measurement. The sensor structure is a combination of a cylindrical piece developed using a 3D printer and a Mach–Zehnder interferometer. The pieces were developed to assist in monitoring the diameter variation. It is formed by splicing an uncoated short section of MMF (Multimode Fiber) between two standard SMFs (Singlemode Fibers) called SMF-MMF-SMF (SMS), where the MMF length is 15 mm. The work is divided into two main parts. Firstly, the sensor was fixed at two points on the first developed piece, and the diameter reduction caused dips or peaks shift of the transmittance spectrum due to curvature and strain influence. The fixation point (FP) distances used are: 5 mm, 10 mm, and 15 mm. Finally, the setup with the best sensitivity was chosen, from first results, to develop another test with an optimization. This optimization is performed in the printed piece where two supports are created so that only the strain influences the sensor. The results showed good sensitivity, reasonable dynamic range, and easy setup reproduction. Therefore, the sensor could be used for diameter variation measurement for proposed applications.

2022

Optical Strain Gauge Prototype Based on a High Sensitivity Balloon-like Interferometer and Additive Manufacturing

Autores
Cardoso, VHR; Caldas, P; Giraldi, MTR; Frazao, O; Costa, JCWA; Santos, JL;

Publicação
SENSORS

Abstract
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 the interference between the core and cladding modes. This is caused by the fiber's curvature because when light propagates through the curved balloon-shaped interferometer region, a portion of it will be released from the core limitation and coupled to the cladding. The balloon has an axial displacement as a result of how the artwork was constructed. The sensor head is sandwiched between two cantilevers such that when there is a displacement, the dimension associated with the micro bend is altered. The sensor response as a function of displacement can be determined using wavelength shift or intensity change interrogation techniques. Therefore, this optical strain gauge is a good option for applications where structure displacement needs to be examined. The sensor presents a sensitivity of 55.014 nm for displacement measurements ranging from 0 to 10 mm and a strain sensitivity of 500.13 pm/mu epsilon.

2022

Temperature-Monitored Fibre Optic Current Sensor Using Channelled-Spectrum Analysis

Autores
Robalinho, P; Melo, M; Frazao, O; Ribeiro, ABL;

Publicação
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract

Teses
supervisionadas

2021

Fabrication of Optofluidic Systems by Femtosecond Laser Micromachining

Autor
João Miguel Mendes da Silva Maia

Instituição
UP-FCUP

2020

Estudo e desenvolvimento de novas configurações de sensores em fibra ótica para monitorização de cristalizadores na área farmacêutica

Autor
Liliana Patrícia Santos Soares

Instituição
UP-FEUP

2020

Raman Endoscopy Using Optical Fiber Technology

Autor
João Pedro Marques

Instituição
UP-FCUP

2020

Optical Fiber Nanowires: Fabrication and Sensing Applications

Autor
André Rodrigues Delgado Coelho Gomes

Instituição
UP-FCUP

2019

Raman Spectroscopy in tumoral tissues

Autor
João Manuel Ribeiro Jordão

Instituição
UP-FCUP