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Publications

Publications by José Luís Santos

2011

Interferometric optical fiber inclinometer with dynamic FBG based interrogation

Authors
da Silveira, CR; Carvalho, JP; Jorge, PAS; Costa, JWA; Giraldi, MTR; Santos, JL; Carvalho Junior, EL; Figueredo, DO; Frazao, O;

Publication
INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS

Abstract
The development of an interferometric optical fiber inclinometer is described in this paper. A weak tapered region is induced in a standard single mode fiber in the vicinity of the cleaved fiber tip, using a standard fusion splicer. In this situation an in-fiber Michelson interferometer is constructed that is sensitive to curvature applied in the tapered region. It is shown that depending on the angular range, fringe visibility and/or peak position depend strongly on the applied curvature enabling low cost dielectric inclinometer to be setup that is suitable for high voltage applications. It is presented an analysis of the sensor response by means of experimental measurements and manipulation of these experimental data through computational simulations. The results coming from the numerical simulations indicate a good performance of the sensor within range of angular variation between 3 and 6 degrees and 10 and 14 degrees. A low cost strategy to interrogate the response of sensor using electrically modulated fiber Bragg gratings, a photodetector and frequency analysis is described. The results presented by this electric interrogation technique show a good sensitivity in the range 3.5 to 5.5 degrees.

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.

2007

Evaluation of coupling losses in hollow-core photonic crystal fibres - art. no. 66191V

Authors
Carvalho, JP; Magalhaes, F; Ivanov, OV; Frazao, O; Araujo, FM; Ferreira, LA; Santos, JL;

Publication
Third European Workshop on Optical Fibre Sensors

Abstract
Hollow-core photonic crystal fibres have a high potential for gas sensing applications, since large light-gas interaction lengths can be effectively attained. Nevertheless, in order to enhance effective diffusion of gas into the fibre hollow-core multi-coupling gaps are needed, which raise coupling loss issues that must be evaluated prior to the development of practical systems. In this communication we present a study on the coupling losses dependence on lateral and axial gap misalignment for single-mode fibre and two different types of hollow-core photonic crystal fibres. In addition, experimental results on the splicing of these fibres are also presented.

2007

In-fibre Mach-Zehnder configuration based on fibre multimode interference structure combined with a long period grating - art. no. 66192H

Authors
Frazao, O; Viegas, J; Caldas, P; Araujo, FM; Ferreira, LA; Santos, JL; Farahi, F;

Publication
Third European Workshop on Optical Fibre Sensors

Abstract
A novel Mach-Zehnder interferometer based on a fibre multimode interference structure combined with a long period fibre grating is proposed. The multimode interference is achieved through the use of a multimode fibre section splices between two sin-le-mode fibres, with a length adjusted to couple a fraction of light into the cladding modes. A LP placed after the multimode fibre couples light back into the fibre core completing the Mach-Zehnder interferometer. The novel configuration was demonstrated as a bending sensor.

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.

2010

Simultaneous Measurement of Strain and Temperature using Modal Interferometry in Bragg Fibers

Authors
Frazao, O; Amaral, LMN; Santos, JL; Roy, P; Jamier, R; Fevrier, S;

Publication
2ND WORKSHOP ON SPECIALTY OPTICAL FIBERS AND THEIR APPLICATIONS WSOF-2

Abstract
In this work it is investigated the strain and temperature sensing characteristics of modal interferometers supported by two Bragg fibers with different cross-section cladding geometries. It is shown that the sensitivity to these measurands is different for the two fibers, which turns feasible the conception of several sensing configurations based on the combination of these two fiber types for simultaneous measurement of strain and temperature.

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