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Publications

Publications by Diana Viegas

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%.

2010

Miniature High-Temperature Fiber Bragg Grating Sensor Design Based on U-Shaped Lossless Taper for Thermal Mapping Applications

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

Publication
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract
A novel design for a miniature fiber Bragg grating-based temperature probe is presented. The sensor integrates a u-shaped lossless taper thus offering the advantages of a terminal temperature probe free from of strain cross-sensitivity and showing installation flexibility while enabling effective serial multiplexing. The experimental validation of the probe design is reported, being demonstrated lossless operation and effective elimination of strain cross-sensitivity up to 400 degrees C.

2011

Simultaneous Measurement of Humidity and Temperature Based on an SiO2-Nanospheres Film Deposited on a Long-Period Grating In-Line With a Fiber Bragg Grating

Authors
Viegas, D; Hernaez, M; Goicoechea, J; Santos, JL; Araujo, FM; Arregui, F; Matias, IR;

Publication
IEEE SENSORS JOURNAL

Abstract
A novel configuration able to measure simultaneously relative humidity and temperature is proposed. The sensing head is based on a long-period fiber grating (LPG) coated with silica nanospheres in-line with a fiber Bragg grating. The polymeric overlay that changes its optical properties when exposed to different humidity levels is deposited onto the LPG using the electrostatic self-assembly technique (ESA), resulting into a humidity-induced shift of the resonance wavelength of the LPG. Considering the humidity range from 20% to 50% RH, a system resolution of 1.6% RH and 2.5 degrees C was achieved. At higher humidity, from 50% to 80% RH, the corresponding resolution values were 2.4% RH and 0.4 degrees C.

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.

2008

Experimental results of antigliadin antibodies detection using long period fiber grating

Authors
Corres, JM; Matias, IR; Goicoechea, J; Arregui, FJ; Viegas, D; Araujo, FM; Santos, JL;

Publication
19TH INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS, PTS 1 AND 2

Abstract
In this work a new nano-biofilm is proposed for the detection of celiac disease (CD). A long-period fiber grating (LPFG) is used as a transducer and the surface of the fiber is coated with a precursor layer of SiO2-nanospheres using the electrostatic self-assembly technique (ESA). This layer has been designed in order to create a substrate of high porosity where the gliadins could be deposited. Under the presence of specific antibodies antigliadin antibodies (AGA) the refractive index of the overlay changes giving a detectable shift in the resonance wavelength of the LPFG. Concentrations as low as 5 ppm were detected.

2008

Humidity sensor based on a long-period fiber grating coated with a SiO2-nanospheres film - art. no. 70044O

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

Publication
19TH INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS, PTS 1 AND 2

Abstract
This work addresses a humidity sensor using long-period fiber gratings (LPG) coated with silica nanospheres film. SiO2-nanospheres coating is deposited onto the LPG using the electrostatic self-assembly technique (ESA). The polymeric overlay changes its optical properties when exposed to different humidity levels, resulting in a shift of the resonance wavelength of the LPG. The obtained results are accordant with the theoretical simulations. Wavelength shifts up to 12nm in a humidity range from 20% to 80% are reported, maintaining the same dependence at different temperatures.

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