Abstract
This paper presents a sensing head based on a Bragg grating written in an elliptical cladding Hi-Bi fibre partially exposed to chemical etching for reduction of the cladding diameter. With this sensing head geometry different strain and similar temperature sensitivities are achieved.

Abstract
An analysis is performed of the degradation of the signal readout of fiber optic Bragg grating sensors demodulated using the serrodyne interferometric technique. Experimental results are presented that validate the analysis. It is also shown that synchronous detection of the interferometric signal referenced to the serrodyne waveform that modulates the phase of the readout interferometer allows the elimination of the system do offset introduced by the serrodyne flyback, (C) 2000 Society of Photo-Optical Instrumentation Engineers.

Abstract
Theoretical and experimental results were presented which validated a new dual interferometric configuration with serrodyne processing for the remote sensing of electrical current. Linearity and waveform reproduction at 50 Hz were observed and a current resolution (˜22.4 ArmsHz- 1/2) was obtained. The utilization of the proposed interferometric concept to simultaneously perform metering and relaying current measurements was also addressed. © 2002 IEEE.

Abstract
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. © 2002 IEEE.

Abstract
Optical fibers are used to provide object and reference illumination in the context of the electronic speckle-pattern interferometry technique. An all-fiber Michelson interferometer is used, with an electronic servo and a piezoelectric phase modulator, to obtain compensation for environmentally induced phase coupling into the fiber arms. © 1990 Optical Society of America.

Abstract
The application of hollow-core photonic crystal fibers for gas sensing is reviewed and discussed. Some problems with splicing to standard fibers and gas diffusion into the core are addressed. Current work at INESC Porto in the development of sensing heads and interrogation units is also reported.