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Publications

Publications by CAP

2002

Characterization of FBGs written in HiBi IEC fibre for multiparameter sensors

Authors
Abe, I; Schiller, MW; Nogueira, RN; Lopes, P; Frazao, O; Santos, JL; Pinto, JL; Kalinowski, HJ;

Publication
2002 IEEE/LEOS ANNUAL MEETING CONFERENCE PROCEEDINGS, VOLS 1 AND 2

Abstract
A simulation characterization with FEM was made, showing that the HiBi fibre was sensitive to different applied load angles. As such, the experimental data for transversal strain was assessed and the obtained sensibility values were in accordance with the simulation results. The collected data enable the complete characterization of the HiBi FBG, showing its capability to be used as a multiparameter sensor.

2002

Sampled fibre Bragg grating sensors for simultaneous strain and temperature measurement

Authors
Frazao, O; Romero, R; Rego, G; Marques, PVS; Salgado, HM; Santos, JL;

Publication
ELECTRONICS LETTERS

Abstract
A new scheme is presented for simultaneous measurement of strain and temperature using a sampled fibre Bragg grating based on a long period structure written using the electric are technique. The temperature and strain measurement resolutions are estimated to be +/-0.50degreesC/rootHz and +/-3.38 muepsilon/rootHz, respectively.

2002

Apodisation of uniform Fibre Bragg Gratings using electric arc discharges

Authors
Rego, G; Romero, R; Frazao, O; Marques, PVS; Salgado, HM;

Publication
PROCEEDINGS OF 2002 IEEE/LEOS WORKSHOP ON FIBRE AND OPTICAL PASSIVE COMPONENTS

Abstract
We report the use of the electric arc technique to apodise Fibre Bragg Gratings (FBG). Electric arc discharges applied at the ends of the grating produce a smoothing of the refractive index modulation profile which reduces the side lobes at longer wavelengths. Using this technique, a FBG was apodised with a side lobe reduction of 17 dB.

2002

Widely tunable L-band erbium doped fiber ring laser by means of induced cavity loss control

Authors
Melo, M; Teixeira, A; Frazao, O; Gomes, L; Lima, M; Santos, C; Pereira, D; Rocha, F; Salgado, HM;

Publication
2002 IEEE/LEOS ANNUAL MEETING CONFERENCE PROCEEDINGS, VOLS 1 AND 2

Abstract
We present and demonstrate a 20 nm tunable L-band fiber ring laser. Tunability is achieved by curving a simple taper which controls the intra-cavity loss.

2002

Simultaneous UV direct writing of channel waveguides and Bragg gratings in germanium-doped planar silica

Authors
Marques, PVS; Bonar, JR; Leite, AMP; Aitchison, JS;

Publication
IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS

Abstract
Channel waveguides incorporating photo-imprinted Bragg gratings were produced in germano-borosilicate glass layers fabricated by flame hydrolysis deposition, through single-and double-step exposure direct writing processes with UV laser irradiation. To our knowledge, this is the first time that UV exposure has been used to simultaneously realize both waveguiding and spectral selectivity functions.

2002

Optical biosensor based on nitrite reductase immobilised in controlled pore glass

Authors
Rosa, CC; Cruz, HJ; Vidal, M; Oliva, AG;

Publication
BIOSENSORS & BIOELECTRONICS

Abstract
The increasing concentration of nitrite in groundwater, rivers and lakes brings serious risks to the public health and to the environment. The aim of this work was the development of an optical biosensor for quantifying nitrite based on the activity of cytochrome cd(1) nitrite reductase immobilised in controlled pore glass (CPG) beads. The developed biosensor operates by measuring the optical reflectance of nitrite reductase, which shows spectroscopic changes when nitrite reversibly binds to the reduced form and oxidises the enzyme. The optimisation of the immobilisation procedure showed that the immobilisation efficiency is highly dependent on the pH, being very low at basic pH, and that the maximum capacity of the CPG for the immobilisation of cd(1) was estimated in 57 +/- 10 mg cd(1)/g CPG. The CPG/cd(1) specific activity remained stable at 4degreesC, decreasing only 10% in 15 days. No observed effects of the immobilisation on the enzyme characteristics were detected, regarding both the red/ox absorbance spectra and the enzyme specific activity, since the red/ox spectra are in good agreement with similar ones obtained for cd(1) in solution, and the specific activity at time zero (0.6 mu moles of NO2- reduced min(-1) mg of protein(-1)) is similar to that found for the soluble enzyme. The biosensor shows a sensitive response to increasing concentrations of nitrite in solution, especially at 460 nm, at which it showed higher sensitivity. The corresponding detection limit of 0.93 muM is well below the maximum admissible concentration imposed by European Community norms, of 2.2 muM.

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