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Publications

Publications by Orlando Frazão

2013

High birefringence triangular optical nanowire in suspended-core fiber for temperature sensing

Authors
Andre, RM; Becker, M; Schuster, K; Rothhardt, M; Bartelt, H; Marques, MB; Frazao, O;

Publication
JOURNAL OF NANOPHOTONICS

Abstract
Triangular nanowires that present a high birefringence and a very strong confinement were fabricated by tapering suspended-core fibers (SCFs) down to core diameters below 1000 nm. Each nanowire presented a high birefringence with an order of magnitude of 10(-3). As the spectra of the SCF tapers inserted in fiber loop mirrors can be used to generate a sinusoidal interference pattern from the two main modes (fast and slow axis), a nanowire was employed as a sensing element in a Sagnac interferometer for measuring temperature. Temperature sensitivity was determined to be -56.2 pm/K using a triangular nanowire of 810 nm in-circle diameter when compared with that of a conventional untapered SCF whose temperature sensitivity is -2.1 pm/K. (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE)

2014

High-sensitivity dispersive Mach -Zehnder interferometer based on a dissimilar-doping dual-core fiber for sensing applications

Authors
Martins, HF; Bierlich, J; Wondraczek, K; Unger, S; Kobelke, J; Schuster, K; Marques, MB; Gonzalez Herraez, M; Frazao, O;

Publication
OPTICS LETTERS

Abstract
A dual-core fiber in which one of the cores is doped with germanium and the other with phosphorus is used as an in-line Mach-Zehnder dispersive interferometer. By ensuring an equal length but with different dispersion dependencies in the interferometer arms (the two cores), high-sensitivity strain and temperature sensing are achieved. Opposite sensitivities for high and low wavelength peaks were also demonstrated when strain and temperature was applied. To our knowledge this is the first time that such behavior is demonstrated using this type of in-line interferometer based on a dual-core fiber. A sensitivity of (0.102 +/- 0.0020 nm/mu epsilon, between 0 and 800 mu epsilon) and (-4.2 +/- 0.2 nm/degrees C between 47 degrees C and 62 degrees C) is demonstrated. (C) 2014 Optical Society of America

2014

In vivo measurement of the pressure signal in the intervertebral disc of an anesthetized sheep

Authors
Roriz, P; Ferreira, JMC; Potes, JC; Oliveira, MT; Frazao, O; Santos, JL; de Oliveira Simoes, JAD;

Publication
JOURNAL OF BIOMEDICAL OPTICS

Abstract
The purpose of the present study was to measure the intradiscal pressure signal of an anesthetized sheep under spontaneous breathing. An ultra-miniature fiber optic high-pressure sensor was implanted into the nucleus pulposus of the fifth lumbar intervertebral using a dorsolateral transforaminal approach. Results suggested the periodicity of the intradiscal pressure signal was similar to the mean respiratory rate of the animal. The average resting intradiscal pressure was also calculated and compared to available data. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)

2014

In-line Mach-Zehnder interferometer based on a dissimilar-doping dual-core fiber for high sensitivity strain and temperature sensing

Authors
Martins, HF; Bierlich, J; Wondraczek, K; Unger, S; Kobelke, J; Schuster, K; Marques, MB; Gonzalez Herraez, M; Frazao, O;

Publication
23RD INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS

Abstract
A dual-core fiber in which one of the cores is doped with Germanium and the other with Phosphorus is used as an in-line Mach-Zehnder (MZ) interferometer to perform high sensitivity strain and temperature sensing. Opposite sensitivities for high and low wavelength peaks were demonstrated when strain was applied. To our knowledge this is the first time that such behavior is demonstrated using this type of in-line MZ interferometer based on a dual-core fiber. A sensitivity of (78 +/- 2) pm/mu epsilon, between 0-950 mu epsilon and (1380 +/- 20) pm/degrees C between 45 and 80 degrees C is demonstrated. It was also demonstrated that it is possible to use this configuration for simultaneous measurement of strain and temperature and a matrix equation to calculate them was given.

2014

INTERROGATION AND MULTIPLEXING SYSTEM FOR FIBER LOOP MIRROR COUPLED INTENSITY SENSORS USING OTDR

Authors
Rocco Giraldi, MTMR; Fernandes, CS; Ferreira, MS; de Sousa, MJ; Jorge, P; Costa, JCWA; Santos, JL; Frazao, O;

Publication
MICROWAVE AND OPTICAL TECHNOLOGY LETTERS

Abstract
In this article, it is proposed an interrogation and multiplexing system based on optical time domain reflectometer for fiber loop mirror coupled intensity sensors. Pulse width of approximately 100 ns enabled to attain a dynamic range of approximately 18 dB. Good linearity was achieved with a -13.3 dB/mm slope. The resolution of the sensing head was 0.027 mm. The proposed interrogation system showed to be an alternative technique for multiplexing and remote sensing. (C) 2014 Wiley Periodicals, Inc.

2013

Interrogation Sensing Scheme Based on a Figure-of-Eight Fiber Loop Mirror

Authors
Silva, RM; Layeghi, A; Zibaii, MI; Latifi, H; Santos, JL; Ribeiro, ABL; Frazao, O;

Publication
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract
A fiber optic interrogation sensor scheme based on a "figure-of-eight" configuration created from a single directional 3 x 3 fiber optic coupler is proposed. Two loops are formed in each arm and one of them contains the sensing head and the other is used as reference signal. A theoretical study based on Jones matrix analysis of this fiber loop mirror combination is reported. The optical configuration is tested as an interrogation scheme for a fiber strain sensor where the spectral response arises from the combination of the reference signal modulated by the sensor signal. The strain sensor configuration shows a phase sensitivity of 6.7 +/- 4.38 x 10(-2) mrad/mu strain by linear regression.

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