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Publicações

Publicações por CAP

2015

Arc-Induced Gratings in the Turning Points

Autores
Colaco, C; Caldas, P; Chibante, R; Rego, G;

Publicação
24TH INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS

Abstract
We demonstrated the inscription of arc-induced long-period fiber gratings (LPFGs) in the B/Ge co-doped fiber and in the SMF28 fiber by using grating periods shorter than 150 mu m and 200 mu m, respectively. This achievement was a result of the development of a high voltage power supply that allows for a constant and stable electric current ranging from 10.5 mA up to 21 mA. The fabricated LPFGs were characterized as a function of the external refractive index from 1.333 up to 1.420 and a refractive index sensitivity of the order of 1000 nm/RIU was obtained without further optimization.

2015

Simulation of Long Period Fibre Gratings and Applications

Autores
Baptista, FD; Guerreiro, A; Gomes, LA; Caldas, P;

Publicação
PROCEEDINGS OF THE INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2014 (ICNAAM-2014)

Abstract
Long-period gratings is class of fiber gratings, in which the period of the refractive index modulation is such that it satisfies a phase matching condition between the fundamental core mode and forward propagating cladding modes of an optical fiber. Many applications in optical communications and optical fiber sensing have been reported along the last years. In this work we present a simulation tool for determining LPG transmission spectrum and the coupling curve. The simulation tool uses MatLab code. The software produces also estimations of the resonant wavelength displacement due to changes in external parameters like temperature or external refractive index. A simple comparison between the simulation and the experimental result show that exist a good agreement with results obtain.

2015

A fiber optic buckle transducer for measurement of in vitro tendon strain

Autores
Roriz, P; Ramos, A; Marques, MB; Simoes, JA; Frazao, O;

Publicação
24TH INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS

Abstract
The purpose of the present study is to present a prototype of a fiber optic based buckle transducer suitable for measuring strain caused by stretching of a tendon. The device has an E-shape and its central arm is instrumented with a fiber Bragg grating (FBG) sensor. The tendon adjusts to the E-form in a fashion that when it is stretched the central arm bends causing a shift of the Bragg's wavelength (lambda(B)) that is proportional to the amount of strain. This prototype is presented as an alternative to conventional strain gauge (SG) buckle transducers.

2015

Acetone evaporation monitoring using a caterpillar-like microstructured fiber

Autores
Gomes, AD; Ferreira, MFS; Moura, JP; Andre, RM; Silva, SO; Kobelke, J; Bierlich, J; Wondraczek, K; Schuster, K; Frazao, O;

Publicação
24TH INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS

Abstract
A new microstructured optical fiber is demonstrated to detect acetone evaporation by observing the time response of the reflected signal at 1550nm. The sensor consists on a caterpillar-like fiber, with a transversal microfluidic channel created with a Focused Ion Beam technique, spliced to a single-mode fiber. Different stages were visible between the dipping and the evaporation of acetone and of a mixture of water and acetone. It was also possible to detect the presence of water vapor.

2015

Bragg Grating Fabrication on Tapered Fiber Tips based on Focused Ion Beam Milling

Autores
Andre, RM; Becker, M; Dellith, J; Rothhardt, M; Zibaii, MI; Latifi, H; Marques, MB; Bartelt, H; Frazao, O;

Publicação
24TH INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS

Abstract
Focused ion beam milling is used on chemically etched tapered fiber tips to create fiber Bragg gratings. These fiber Bragg gratings are based on a modulation of silica and external medium. This leads to a wide and structured spectrum obtained due to imperfections and the inherent structure of the tip. The fiber Bragg gratings presented are very short and have a length of 27 mu m and 43 mu m and are milled on the tapered fiber tip. They are characterized in the high temperature range 350-850 degrees C and a sensitivity of 14.4 pm/K is determined.

2015

Centre of mass determination based on an optical weighing machine using fiber Bragg gratings

Autores
Oliveira, R; Roriz, P; Marques, MB; Frazao, O;

Publicação
24TH INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS

Abstract
The purpose of the present work was to construct a weighing machine based on fiber Bragg gratings (FBGs) for the location of the 2D coordinates of the center of gravity (COG) of objects with complex geometry and density distribution. The apparatus consisted of a rigid equilateral triangular platform mounted on three supports at its vertices, two of them having cantilevers instrumented with FBGs. As an example, two femur bone models, one with and one without a hip stem prosthesis, are used to discuss the changing of the COM caused by the implementation of the prosthesis.

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