2009
Authors
Amaral, LMN; Pereira, DA; Frazao, O; Marques, MB; Lima, MJN; Teixeira, ALJ;
Publication
ICTON: 2009 11TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS, VOLS 1 AND 2
Abstract
An interferometric setup for measuring Polarization Mode Dispersion (PMD) setup was tested. Using a low-coherence technique with a Michelson interferometer, it was possible to measure values of PMD from detected Differential Group Delay (DGD) values in two reels. The low-coherence source bounds the minimum value of DGD detected to 0.13 ps, leading to a minimum value detected around 0.14 ps. The mean value of PMD measured over a period of several days for one reel was 0.0405 +/- 0.0007 ps/km(1/2), and 0.0463 +/- 0.0044 ps/km(1/2) for the other. Stochastic and random behavior of PMD was observed.
2006
Authors
Pinto, NMP; Frazao, O; Romero, R; Costa, A;
Publication
ICTON 2006: 8th International Conference on Transparent Optical Networks, Vol 4, Proceedings: CONFERENCE & COST P 11 TRAINING SCHOOL POSTERS
Abstract
A polarization mode dispersion (PMD) emulator and compensator device is proposed. The PMD device is obtained using a Hi-Bi Fibre Bragg Grating (Hi-Bi FBG) and a stress induced bireffingence in a uniform FBG. This birefringence is achieved by applying transverse and uniform distributed force on the uniform fibre Bragg grating creating a tuneable differential group delay (DGD). Maximum and minimum slopes of 377 ps/nm and 0 ps/mn in the DGD is obtained for the PMD emulator/compensator device, respectively.
2003
Authors
Abe, I; Abe, I; Kalinowski, H; Nogueira, R; Pinto, J; Frazao, O;
Publication
IEE PROCEEDINGS-CIRCUITS DEVICES AND SYSTEMS
Abstract
Bragg gratings written in high-birefringence fibre optics are a key element in the simultaneous measurement of transversal strain components and temperature, and they have several applications as single polarisation optical filters for wavelength division multiplexing (WDM) applications. Precise determination of grating characteristics is needed to aid device design, particularly taking into account the polarisation of the illuminating light. The authors report results concerning the production and characterisation of Bragg gratings in high birefringence fibre. Birefringence is measured by the wavelength dependence of the beat length, and from the Bragg grating reflection bands, for three common high birefringence fibres. Characterisation of the gratings when subjected to transversal strain and temperature is described, as well as results of the use of the grating to measure, simultaneously, those two parameters.
2012
Authors
Silva, RM; Ferreira, MS; Frazao, O;
Publication
OPTICS COMMUNICATIONS
Abstract
A high-birefringent (Hi-Bi) Sagnac loop interferometer for torsion measurement is demonstrated. The sensing head is formed by a section of standard single mode fiber spliced between the output ports of a Hi-Bi coupler at 3 dB. The sensing configuration is characterized in torsion, temperature and strain. The results obtained indicate the viability of a torsion sensor independent of the temperature and strain cross-sensitivity effects. Additionally, in the proposed configuration all measurements are performed without the need of a polarization controller, a device most often required in standard Sagnac loops applied for sensing.
2012
Authors
Ponmozhi, J; Frias, C; Marques, T; Frazao, O;
Publication
MEASUREMENT
Abstract
This paper reflects on review of smart sensor activities for biomedical applications. The rise of biotechnology has provided innovative development of new therapies and detection methods for life threatening diseases. As a worldwide research focus, there is especially a strong interest in the use of microsystems in health care, particularly as smart implantable devices. Recent years have seen an increasing activity of hip and knee replacement and other type of implants, which are some of the most frequently performed surgical procedures in the world. Loosening of hip prosthesis is the dominant issue for many patients who undergo a hip arthroplasty. Artificial joints are subject to chronic infections associated with bacterial biofilms, which only can be eradicated by the traumatic removal of the implant followed by sustained intravenous antibiotic therapy. This review focuses on the clinical experience using all kinds of smart implants like orthopedic implants instrumented with strain gauges, retina implant system using image sensors. Technical design improvements will enhance function, quality of life, and longevity of total knee arthroplasty and all other kind of implants. Application of biocompatible nanomaterials in implantable biosensors for continuous monitoring of metabolites is an area of sustained scientific and technological interests. Crown Copyright
2010
Authors
Frias, C; Faria, H; Frazao, O; Vieira, P; Marques, AT;
Publication
MATERIALS & DESIGN
Abstract
In this research programme, methodologies for structural health monitoring (SHM) of composite over-wrapped pressure vessels (COPV) were addressed. So, this work is part of the development of a COPV laboratorial prototype incorporated with non-destructive sensing technologies. The aim is to detect and identify critical aspects that can happen during operation, in order to reduce possible safety problems. Fibre Bragg grating (FBG) optical sensors and polyvinylidene fluoride (PVDF) polymeric piezoelectric were the selected sensing technologies. These sensors were embedded in the liner-composite interface during its manufacturing and monitored the prototype while tested under cyclic internal pressure loading. The measurements collected from the sensors were compiled with the analysis of test data and are presented in this paper. Also, the suitability of the two sensing technologies, issues related to sensor embedding and the monitoring strategy are discussed.
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