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400 results on '"Frazao, O."'

1. Microfiber Knot Resonators for Sensing Applications

Author

Gomes, A. D., Frazão, O., Adibi, Ali, Series Editor, Asakura, Toshimitsu, Series Editor, Hänsch, Theodor W., Series Editor, Krausz, Ferenc, Series Editor, Masters, Barry R., Series Editor, Venghaus, Herbert, Series Editor, Weber, Horst, Series Editor, Weinfurter, Harald, Series Editor, Midorikawa, Katsumi, Series Editor, Rhodes, William T., Editor-in-Chief, Ribeiro, Paulo, editor, Andrews, David L., editor, and Raposo, Maria, editor

Published
2019
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20. Simultaneous measurement of multiparameters using a Sagnac interferometer with polarization maintaining side-hole fiber

Author

Frazao, O., Silva, S.O., Baptista, J.M., Santos, J.L., Statkiewicz-Barabach, G., Urbanczyk, W., and Wojcik, J.

Subjects
Interferometers -- Usage, Polarization (Light) -- Research, Fiber optics -- Research, Diffraction patterns -- Research, Fiber optics, Astronomy, Physics
Abstract

A Sagnac interferometer with a section of a polarization maintaining side-hole fiber for multiparameter measurement is proposed. The sensor was experimentally demonstrated to be sensitive to torsion, temperature, and longitudinal strain, simultaneously. The birefringence in the investigated side-hole fiber is induced simultaneously by the elliptical shape of a germanium-doped core and by field overlap with the air holes surrounding the core. The latter effect is purely geometrical and causes high chromatic dispersion of the group birefringence in the long wavelength range, which results in a different period of spectral interference fringes. A different wavelength response is obtained for each interference fringe peak when the fiber is subjected to torsion, temperature, or longitudinal strain. A matrix equation for simultaneous measurement of the three parameters--torsion, temperature, and longitudinal strain is also proposed. OCIS codes: 060.0060, 060.2370, 060.2420.

Published
2008

23. Intensity-referenced and temperature-independent curvature-sensing concept based on chirped fiber Bragg gratings

Author

Romero, R., Frazao, O., Pereira, D.A., Salgado, H.M., Araujo, F.M., and Ferreira, L.A.

Subjects
Diffraction gratings -- Research, Optics -- Research, Fiber optics -- Equipment and supplies, Fiber optics -- Research, Astronomy, Physics
Abstract

An intensity-referenced temperature-independent curvature-measurement technique that uses a smart composite that comprises two chirped fiber Bragg gratings is demonstrated. The two gratings are embedded on opposite sides of the composite laminate and act simultaneously as curvature sensors and as wavelength discriminators, enabling a temperature-independent intensity-based scheme to measure radius of curvature. Also, the system's performance is independent of arbitrary power losses that are induced in the lead fibers to the sensing head. It is demonstrated that the measurement range depends on the relative positions of the chirped fiber Bragg gratings and on their spectral bandwidths. By using two chirped fiber Bragg gratings with bandwidths [W.sub.1] = 2.8 nm and [W.sub.2] = 3.7 nm and with central wavelengths at [[Angstrom].sub.01] = 1560.3 nm and [[Angstrom].sub.02] = 1563.7 nm, we obtained a resolution of 1.6 mm/[square root of Hz] for the measurement of the radius of curvature (~R = 350 mm) over the measurement range 190 mm < R < [infinity]. OCIS codes: 060.2370, 060.2340.

Published
2005

32. The angular momentum of vectorial non-paraxial fields and the role of radial charges in orbit-spin coupling.

Author

Michinel, H., Costa, M.F., Frazao, O., El Gawhary, Omar, and Urbach, Paul

Subjects
ANGULAR momentum (Mechanics), ELECTROMAGNETIC radiation, OPTICAL properties, OPTICAL elements, COMPUTED tomography
Abstract

Electromagnetic fields carry a linear and an angular momentum, the first being responsible for the existence of the radiation pressure and the second for the transfer of torque from electromagnetic radiation to matter. The angular momentum is considered to have two components, one due to the polarization state of the field, usually called Spin Angular Momentum (SAM), and one due to existence of topological azimuthal charges in the field phase profile, which leads to the Orbital Angular Momentum (OAM). For non-paraxial fields these two contributions are not independent of each other, something which is described as spin-orbit coupling. It has been recently proved that electromagnetic fields necessarily carry also invariant radial charges that, as discussed in this work, play a key role in the angular momentum. Here we show that the total angular momentum consists in fact of three components: one component only dependent on the spin of the field, another dependent on the azimuthal charges carried by the field and a third component dependent on the spin and the radial charges contained in the field. By properly controlling the number and coupling among these radial charges it is possible to design electromagnetic fields with a desired total angular momentum. In this way it is also possible to discover fields with no orbital angular momentum and a spin angular momentum typical of spin-3/2 objects, irrespective of the fact that photons are spin-1 particles. [ABSTRACT FROM AUTHOR]

Published
2020
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33. Introducing Full-Aperture FJP (faFJP), a Technique for Manufacturing Sub-Millimetre Aspheres.

Author

Michinel, H., Costa, M.F., Frazao, O., Messelink, W.A.C.M., and Meeder, M.

Subjects
AUTOMATION, PLASMA jets, ATMOSPHERIC pressure, OPTICAL properties, OPTICAL glass
Abstract

We propose a novel approach, "faFJP", to the computer controlled polishing (CCP) of mini aspheres down to 0:2 mm. The generation of locallytunable, full-aperture footprints is accomplished by applying a Fluid Jet Polishing (FJP) beam larger than the full aperture being polished and varying the incident angle. [ABSTRACT FROM AUTHOR]

Published
2020
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35. PanDao fabrication cost impact analysis software tool for optical designers.

Author

Michinel, H., Costa, M.F., Frazao, O., Tinner, Marco, Livshits, Irina, and Faehnle, Oliver

Subjects
OPTICAL properties, OPTICAL elements, KINEMATICS, ABRASIVE machining, METROLOGY
Abstract

A new software tool, called PanDao, for optical system designers is presented enabling during the design stage a simulation of the optimum fabrication chain and technologies needed as well as a fabrication cost impact analysis of design parameters and tolerances. [ABSTRACT FROM AUTHOR]

Published
2020
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39. Fabry-Perot refractometer based on an end-of-fiber polymer tip

Author

Frazao, O., Caldas, P., Santos, J.L., Turck, Colette, Lougnot, Daniel, Soppera, Olivier, Instituto de Engenharia de Sistemas e Computadores Investigação e Desenvolvimento em Lisboa (INESC-ID), Instituto Superior Técnico, Universidade Técnica de Lisboa (IST)-Instituto de Engenharia de Sistemas e Computadores (INESC), Departement de Photochimie Générale, Ecole Nationale Supérieure de Chimie de Mulhouse, and Turck, Colette

Subjects
[CHIM.MATE] Chemical Sciences/Material chemistry, [CHIM.POLY] Chemical Sciences/Polymers, [CHIM.POLY]Chemical Sciences/Polymers, [CHIM.MATE]Chemical Sciences/Material chemistry, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2009

40. Curvature Sensor based on a Fibre Loop Mirror using a Highly Birefringent Photonic Crystal Fibre with Assymetric Hole Regions

Author

Frazao, O., Baptista, J.M., Santos, J.L., Roy, Philippe, PHOTONIQUE, XLIM (XLIM), Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS)-Université de Limoges (UNILIM)-Centre National de la Recherche Scientifique (CNRS), and Lebraud, Sophie

Subjects
4225L, 0707D, Biréfringence, Physics::Optics, Capteur optique, Fibre optique, Méthode mesure, 4281P, Miroir, 0130C, Capteur fibre optique, Méthode optique, Déformation mécanique, Fibre microstructurée
Abstract

International audience; In this work, a curvature sensor based on a highly birefringent (Hi-Bi) photonic crystal fibre loop mirror is presented. For this purpose, a novel Hi-Bi photonic crystal fibre was designed and fabricated. Half of the microstructured region of the photonic crystal fibre was composed by holes with large diameter, while the other half contained holes with small diameter. Due to this geometry, the fibre core was shifted from the centre and high birefringence appears in the optical fibre. The Hi-Bi photonic crystal fibre loop mirror was demonstrated as a curvature sensor. The curvature was applied for three different fibre directions for the range of 0.6 - 5 metres-1. The configuration was also characterized for temperature and longitudinal strain, showing insensitivity for these two physical parameters.

Published
2008

48. Research of the optical communications groups at University of Aveiro and Institute of Telecommunications - Aveiro Pole

Author

Da Rocha, J. F., Tavares, P., Frazao, O., Monteiro, P., Andre, P. S., Teixeira, A., Lima, M., Pinto, A. N., Atilio Gameiro, Ribeiro, R., Ribeiro, L., Cunha, A., Pinto, J. L., Ferreira, M. R., and Pousa, M.

Subjects
EDFA, WDM, Clock Recovery, Equalizer, Optical receivers, DST, Timing Jitter, Solitons
Abstract

This paper summarizes the research activities of the optical communications group at University of Aveiro and Institute of Telecommunications – Aveiro pole. Several activities like clock recovery systems, both electrical and all optical, electrical equalizers for very high bit rate DST systems, post-detection filters for multigigabit optical receivers, soliton systems, simulation work on WDM, DST, EDFA and short pulse generation for high bit rate systems are presented.

Published
1999

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