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Publicações

Publicações por José Luís Santos

2018

Temperature Compensated Strain Sensor Based on Long-Period Gratings and Microspheres

Autores
Ascorbe, J; Coelho, L; Santos, JL; Frazao, O; Corres, JM;

Publicação
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract
In this letter, we present a new structure composed by a long-period grating (LPG) and a microsphere in series, which works as a modal interferometer besides allowing the mode coupled to the cladding to be coupled back to the core. The LPG was written by the electric arc technique and the microsphere was fabricated using a splicing machine. It is possible to use this new structure for simultaneous measurement of strain and temperature. It also allows one to obtain a temperature compensated strain sensor by using a proper data processing algorithm, which utilizes two distinct wavelengths for strain and temperature. Then, a strain sensitivity of 0.86 pm/mu epsilon and a reduced temperature sensitivity of 0.7 pm/degrees C were achieved.

2017

Phase-interrogated SPR sensing structures based on tapered and tip optrode optical fiber configurations with bimetallic layers

Autores
Moayyed, H; Leite, IT; Coelho, L; Santos, JL; Viegas, D;

Publicação
MEASUREMENT SCIENCE AND TECHNOLOGY

Abstract
This work reports the theoretical investigation of optical fiber surface plasmon resonance sensors incorporating bimetallic layer combinations. Different metals like silver, gold, copper, and aluminum are considered to investigate the refractometric sensing properties of tapered and tip optrode phase-interrogated optical fiber plasmonic sensor structures. It is shown that the gold-silver combination, coupled to a tip optrode layout, is capable of maximizing the resolution and operation range of these sensing structures for environmental refractive index measurement.

2014

Reflection-Based Phase-Shifted Long-Period Fiber Grating for Cryogenic Temperature Measurements

Autores
Martins, R; Monteiro, J; Caldas, P; Santos, JL; Rego, G;

Publicação
23RD INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS

Abstract
In this work, we propose a compact sensor head to perform cryogenic temperature measurements based on a long-period fiber grating. The presented configuration enables the sensor to be interrogated in reflection since a phase-shifted is produced by Fresnel reflection on the end-face of the fiber, cleaved at a quarter-period separation distance from the end of the grating.

2013

Simplified sensor design for temperature-strain discrimination using Fiber Bragg Gratings embedded in laminated composites

Autores
Rodriguez Cobo, L; Marques, AT; Lopez Higuera, JM; Santos, JL; Frazao, O;

Publicação
Proceedings of SPIE - The International Society for Optical Engineering

Abstract
Several easy-to-manufacture designs based on a pair of Fiber Bragg Gratings structure embedded in Carbon Fiber Reinforced Plastic (CFRP) have been explored. These smart composites can be used for strain and temperature discrimination. A Finite Elements Analysis and Matlab software were used to study the mechanical responses and its optical behaviors. The results exhibited different sensitivity and using a matrix method it is possible to compensate the thermal drift in a real application keeping a simple manufacture process. © 2013 SPIE.

2015

Simultaneous measurement of strain and temperature based on clover microstructured fiber loop mirror

Autores
Perez Herrera, RA; Andre, RM; Silva, SF; Becker, M; Schuster, K; Kobelke, J; Lopez Amo, M; Santos, JL; Frazao, O;

Publicação
MEASUREMENT

Abstract
In this work, two all-fiber loop mirrors using a clover microstructured fiber for the simultaneous measurement of temperature and strain are presented. The sensing heads are formed by a short piece of clover microstructured fiber with 35 mm and 89 mm length respectively. The geometry of the fiber allowed observing different interferences created by the microstructured fiber core section. Different sensitivities to temperature and strain were obtained and, using a matrix method, it is possible to discriminate both physical parameters. Resolutions of +/- 2 degrees C and +/- 11 mu epsilon for the first structure and +/- 2.3 degrees C and +/- 18 mu epsilon for the second one, for temperature and strain, respectively, were attained.

2015

Theoretical Study of Phase-Interrogated Surface Plasmon Resonance Based on Optical Fiber Sensors with Metallic and Oxide Layers

Autores
Moayyed, H; Leite, IT; Coelho, L; Santos, JL; Viegas, D;

Publicação
PLASMONICS

Abstract
This work reports the theoretical investigation of optical fiber surface plasmon resonance sensors incorporating an internal metallic layer of silver covered with an oxide layer. This research is supported by the application of an effective analytical model combining geometrical optics with the transfer matrix theory for stratified optical media. Different oxide materials like titanium dioxide, silicon dioxide, and aluminum oxide are considered aiming to achieve increased/enhanced sensitivity to refractive index variations of the external medium, particularly when addressing phase interrogation. It is shown that the combination of a 50-nm thickness silver inner layer with a dielectric titanium oxide layer of a specific thickness enables high-performance phase sensitivity reading and is compatible with tailoring the sensor working region to the third telecommunication wavelength window around 1550 nm.

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