2012
Authors
Layeghi, A; Zibaii, MI; Sadeghi, J; Frazao, O; Jorge, PAS; Latifi, H;
Publication
22ND INTERNATIONAL CONFERENCE ON OPTICAL FIBER SENSORS, PTS 1-3
Abstract
A high-birefringent fiber (HBF) was tapered as adiabatic in sequence steps by utilizing a CO2 laser and its birefringence was measured in fiber loop mirror (FLM) setup. The birefringence of tapered section and total sensor was obtained to be -8.02x10(-2), and 2.46x10(-4), respectively. Then, refractive index (RI) sensitivity increased and temperature sensitivity of the tapered Hi-Bi fiber (THBF) decreased. The sensitivity of the proposed FLM interferometer for RI changes in the range from 1.3380 to 1.3470 was measured to be 389.85 nm/RIU. The temperature sensitivity in the range from 50 degrees C to 90 degrees C was measured to be -1.19nm/degrees C.
2012
Authors
Zibaii, MI; Nouri, S; Sadeghi, J; Latifi, H; Jorge, PAS; Schuster, K; Kobelke, J; Frazao, O;
Publication
22ND INTERNATIONAL CONFERENCE ON OPTICAL FIBER SENSORS, PTS 1-3
Abstract
In this work, fiber in-line Mach-Zehnder Interferometer (MZI) based on triangular-shape suspended core fibers (SCFs) is investigated. The sensitivity of the sensing head was determined for pressure and temperature, respectively. The sensitivities are 0.4 pm/psi and 13 pm/psi for longitudinal and radial pressure, respectively. The sensing head was also subjected to temperature and presented very low sensitivity.
2010
Authors
Queiros, RB; Silva, SO; Sales, MGF; Noronha, JP; Frazao, O; Jorge, PAS; Aguilar, GG;
Publication
FOURTH EUROPEAN WORKSHOP ON OPTICAL FIBRE SENSORS
Abstract
The deterioration of water quality by Cyanobacteria causes outbreaks and epidemics associated with harmful diseases in Humans and animals because of the released toxins. Microcystin-LR (mcyst) is one of the most widely studied hepatotoxin and World Health Organization recommends a maximum value of 1 mu g L-1 of mcyst in drinking-water. Therefore, there is a great demand for remote, real-time sensing techniques to detect and quantify the presence of mcyst. In this work a Fabry-Perot sensing probe based on a fibre tip coated with a mcyst sensitive thin film is presented. Highly specific recognition membranes, using sol-gel based Molecular Imprinted Polymers (MIPs), were developed to quantify microcystins in water, showing great potential in the analysis of this kind of samples. The fibre Fabry-Perot MIP sensor shows a linear response to mcyst concentration with a sensitivity of -13.2 +/- 0.4 nm L mu g(-1).
2010
Authors
Tafulo, PAR; Frazao, O; Jorge, PAS; Araujo, FM;
Publication
FOURTH EUROPEAN WORKSHOP ON OPTICAL FIBRE SENSORS
Abstract
An intrinsic Fabry-Perot cavity for high temperature and strain measurement is presented. The in-fibre cavity is formed by a chemical etched graded index optical fiber spliced to a single mode fiber. The intrinsic sensor obtained shows high sensitivity to strain (6.2 pm/mu epsilon) and rather low sensitivity to temperature (0.9 pm/degrees C), being suitable for applications as a strain gauge at high temperature.
2011
Authors
Zibaii, MI; Jorge, PAS; Frazao, O; Latifi, H;
Publication
INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS
Abstract
A single-mode non-adiabatic tapered optical fiber (NATOF) sensor was inserted into a Sagnac loop interferometer allowing tuning its sensitivity to refractive index (RI) by use of polarization control. By adjusting any polarization controllers inserted in the Sagnac loop interferometer, various cladding modes are selectively excited in each arm of the interferometric taper resulting into different phase changes for the clockwise and counterclockwise beams. By this method, sensitivity of the sensor for RI in the range from 1.3380 to 1.3510 was tuned between 876.24 RIU/nm to 1233.07 RIU/nm.
2000
Authors
Novo, C; Frazao, O; Costa, AN; Vieira, A; Correia, N; Dias, I; Araujo, FM; Marques, AT;
Publication
14TH INTERNATIONAL CONFERENCE ON OPTICAL FIBER SENSORS
Abstract
Monitoring and control of RTM process is essential to minimise trial and errors and optimise cycle productions. Hence a research programme was established to study different systems to control the process. In this paper, several experiments are described in which an on-line system based on fibre Bragg sensors was implemented.
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