Examinando por Autor "Santos, J. L."

Mostrando 1 - 3 de 3

Restringido
A study of the optical properties of photopolymer Fabry-Perot microcavities by a dual-wavelength fibre optic architecture
(IOP Science Publishing, 2002-06-20) López Heredero, R.; Martín, S.; Fernández de Caleya, R. F.; Lobo Ribeiro, A. B.; Araújo, F. M.; Ferreira, L. A.; Santos, J. L.; Guerrero, H.; 0000-0002-7047-0273; 0000-0002-2988-1222; 0000-0003-2922-3489; 0000-0002-2197-8388; 0000-0002-0818-4268
We present a novel method to study the behaviour of the optical properties of photopolymer materials with temperature. The photopolymer is deposited on the tip of optical fibres by dip coating to fabricate low-finesse Fabry-Perot microcavities. The signal processing technique utilized to interrogate the cavity is based on the generation of two quadrature phase-shifted interferometric signals using two Bragg fibre gratings. This technique enables the determination of the values of the thermo-optical coefficient and the linear coefficient of thermal expansion of the photopolymer. The effectiveness of the processing technique is also exploited in the study of the dependence of the temperature sensitivity on the cavity thickness.
Restringido
Micromachined low-finesse Fabry-Perot interferometer for the measurement of DC and AC electrical currents
(Institute of Electrical and Electronics Engineers, 2003-04-22) López Heredero, R.; Santos, J. L.; Fernández de Caleya, R. F.; Guerrero, H.; López Heredero, R. [0000-0002-2197-8388]; Guerrero, H. [0000-0003-2922-3489]; Santos, J. L. [0000-0002-0818-4268]
A micromachined low finesse Fabry-Perot interferometer for measuring DC and AC electrical current is presented. Interrogation of the microcavity is achieved by a dual-wavelength fiber Bragg grating technique working in quadrature. A linear relation between the DC electrical current and the optical phase defined by the microcavity was detected. Large enhancement of the sensitivity of the microcavities is presented with the use of a planar coil instead of a power line. The sensitivity of the sensor with the planar coil configuration is 7.9 rad/A and resolution of ∼0.18 mA//spl radic/Hz is achieved when the distance between the planar coil and the transducer head is 2 mm. The response of the sensor for AC measurements is 0.14 V/A with a resolution of 6 mA//spl radic/Hz when the distance between the power line and the transducer head is 5.5 cm.
Restringido
Micromachined low-finesse Fabry-Perot interferometer for the measurement of low DC electrical currents
(Institute of Electrical and Electronics Engineers, 2002-05-10) López Heredero, R.; Santos, J. L.; Fernández de Caleya, R. F.; Araújo, F. M.; Ferreira, L. A.; Guerrero, H.; Guerrero, H. [0000-0003-2922-3489]; López Heredero, R. [0000-0002-2197-8388]
An optical fiber current sensor based on a permanent magnet fixed on the center of a micromachined Si membrane has been presented. The transducing operation principle is magneto-mechanical and has a linear response. A great improvement of the sensitivity of the microcavities was achieved by the use of a planar coil. Interrogation of the transducer has been carried out using a Fabry-Perot interferometer with an all-fiber detection system to avoid the influence of electromagnetic noise. The effectiveness of a fiber scheme based on the utilization of two fibre Bragg gratings to generate two quadrature phase-shifted interferometric signals has also been reported.