Publications

Publications by CRAS

2009

<title>Non-terminal miniature fiber Bragg grating temperature probe based in U-shape lossless taper</title>

Authors
Viegas, D; Abad, S; Santos, JL; Ferreira, LA; Araújo, FM;

Publication
20th International Conference on Optical Fibre Sensors

Abstract

2009

<title>Fibre Bragg gratings as interrogation elements for surface plasmon resonance sensors</title>

Authors
Díaz-Herrera, N; Viegas, D; Jorge, PAS; Navarrete, MC; Ferreira, LA; Araújo, FM; Santos, JL; González-Cano, A;

Publication
20th International Conference on Optical Fibre Sensors

Abstract

2009

Sensitivity Improvement of a Humidity Sensor Based on Silica Nanospheres on a Long-Period Fiber Grating

Authors
Viegas, D; Goicoechea, J; Santos, JL; Araujo, FM; Ferreira, LA; Arregui, FJ; Matias, IR;

Publication
SENSORS

Abstract
This work addresses a new configuration that improves the sensitivity of a humidity sensor based on a long-period fiber grating coated with a SiO(2)-nanospheres film. An intermediate higher refractive index overlay, deposited through Electrostatic Self-Assembly, is placed between the fiber cladding and the humidity sensitive film in order to increase the total effective refractive index of the coating. With this intermediate design, a three-fold improvement in the sensitivity was obtained. Wavelength shifts up to 15 nm against 5 nm were achieved in a humidity range from 20% to 80%.

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2009

A fibre optic humidity sensor based on a long-period fibre grating coated with a thin film of SiO2 nanospheres

Authors
Viegas, D; Goicoechea, J; Corres, JM; Santos, JL; Ferreira, LA; Araujo, FM; Matias, IR;

Publication
MEASUREMENT SCIENCE & TECHNOLOGY

Abstract
A novel sensing configuration for measuring humidity based on a long-period fibre grating coated with a thin film of silica nanospheres is proposed. The polymeric overlay is deposited on the grating using the electrostatic self-assembly technique. This thin film changes its optical properties when exposed to different humidity levels that translate into a shift of the resonance wavelength of the fibre grating. Wavelength shifts up to 12 nm in a relative humidity range from 20% to 80% are reported, and it is further demonstrated that such humidity sensitivity has negligible thermal dependence.

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2009

Non-terminal miniature fiber Bragg grating temperature probe based in U-shape lossless taper

Authors
Viegas, D; Abad, S; Santos, JL; Ferreira, LA; Araujo, FM;

Publication
Proceedings of SPIE - The International Society for Optical Engineering

Abstract
A novel miniature fiber Bragg grating (FBG) based temperature probe is presented. The sensor design integrates a ushape lossless taper thus offering the advantages of a terminal temperature probe while enabling effective serial multiplexing. We report on the experimental validation of the temperature probe design demonstrating lossless operation and effective elimination of strain cross-sensitivity. © 2009 SPIE.

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2009

Fibre Bragg gratings as interrogation elements for surface plasmon resonance sensors

Authors
Diaz Herrera, N; Viegas, D; Jorge, PAS; Navarrete, MC; Ferreira, LA; Araujo, FM; Santos, JL; Gonzalez Cano, A;

Publication
Proceedings of SPIE - The International Society for Optical Engineering

Abstract
A new interrogation method based on Fibre Bragg Gratings (FBG) for Surface Plamon Resonance (SPR) sensors in the region of refractive indices of aqueous solutions is described. Two FBGs are selected with their Bragg wavelengths at opposite sides of the plasmon resonance peak. The response of the system can be made independent of the fluctuations of the optical power source, and the linearity and the sensitivity of the sensor are improved. The use of the spectral selectivity of gratings for the interrogation of SPR sensors in different configurations is also promising in terms of multiplexing, temperature referencing or multiparameter detection. © 2009 SPIE.

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