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Publicações

Publicações por CAP

2014

New Silica Microspheres Array Sensor

Autores
Ferreira, MS; Santos, JL; Frazao, O;

Publicação
23RD INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS

Abstract
In this work a novel optical fiber sensor based on silica microspheres array is proposed. Different sensing heads are presented and compared, differing on the number of microspheres. These structures, ranging from arrays of one to five, are spliced in series. The sensor is subjected to different physical parameters, such as strain, temperature, refractive index and bending. Depending on the number of microspheres the sensitivities to strain and bending are different. The sensor also presents a high sensitivity to temperature of 20.3 pm/degrees C.

2014

Optical Fiber Refractive Index Sensor with Reduced Thermal Sensitivity based on Superimposed Long-Period Gratings

Autores
Silva, GE; Caldas, P; Santos, JC; Santos, JL;

Publicação
23RD INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS

Abstract
In this paper, we report the development of a reduced temperature sensitivity optical fiber sensor for refractive index measurement based on Superimposed Long-Period Gratings (SLPG) inscribed by the electric arc technique in standard fiber. The reduced sensitivity to temperature is achieved by calculation of the difference between resonance wavelengths of two guided cladding modes.

2014

Optical Inclinometer Based on a Phase-Shifted Bragg Grating in a Taper Configuration

Autores
Moura, JP; Silva, SO; Becker, M; Rothhardt, M; Bartelt, H; Santos, JL; Frazao, O;

Publicação
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract
A simple optical inclinometer based on a phase-shifted Bragg grating in a taper configuration is proposed. Two phase-shifted fiber Bragg gratings were fabricated using a DUV femtosecond laser technique in the taper region, with taper waist diameters of 30 mu m and 50 mu m. Both sensing heads were compared based on their response to angle and strain. Whereas the higher diameter sensor yielded a higher sensitivity to curvature (23.8 +/- 0.3 pm/degree), the lower diameter one was more sensitive to strain (8.94 +/- 0.04 pm/mu epsilon).

2014

Optical Phase Refractometer Based on Post-Processed Interferometric Tip Sensors

Autores
Ferreira, MS; Bierlich, J; Unger, S; Schuster, K; Santos, JL; Frazao, O;

Publicação
JOURNAL OF LIGHTWAVE TECHNOLOGY

Abstract
An interferometric tip sensor based on the post-process of a special design double-cladding optical fiber is proposed. Due to the sensing head design, it is sensitive to environmental variations. In order to analyze this effect, the sensing head is subjected to temperature variations both in liquid and gas (at 1 atm). Comparing the two signals, it is possible to discriminate the contribution of the liquid refractive index variation with temperature. Not only the amplitude of the signal varies with the surrounding medium, but also the phase of the interferometric pattern alters. This is due to the presence of a thin diaphragm at the end face of the fiber structure turning the sensing head in a three wave interferometric device. An indirect measurement of the water refractive index is performed, by subjecting the sensing head to temperature variations in air and water. Even though the sensitivities obtained are lower than the ones reported in the literature, it should be highlighted that there is no core exposition of the fiber to the external medium. The sensor is easy to fabricate, robust, and reproducible.

2014

Optical sensing based in plasmonics and the metamaterials enhancement factor

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

Publicação
Latin America Optics and Photonics Conference, LAOP 2014

Abstract
The recent burst of R&D activity in Plasmonics, associated with the possibility of materials nanostructuring which enables the access to metamaterials, has been strongly impacting many branches of optics such as imaging, data recording and sensing. This talk details the factors that turned the combination Plasmonics and Metamaterials a huge opportunity to optical sensing.© OSA 2014.

2014

Post-processing fibers for sensing applications

Autores
Frazao, O; Ferreira, MS; Andre, RM; Silva, SO; Marques, MB; Santos, JL;

Publicação
Optical Sensors, 2014

Abstract
A review in fiber post-processing for sensing applications is presented. The review is divided in three parts. Tapers devices, chemical etching for Fabry-Perot cavities and focused ion beam (FIB) as post-processing applied in optical fibers are considered. The most recent results as sensing elements are shown. © 2014 OSA.

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