Showing papers by "Pietro Ferraro published in 1995"

Embedded optical sensor capable of strain and temperature measurement using a single diffraction grating

Abstract: An embedded optical sensor has a plurality of layers (10-20) and an optical fiber (21) with a fiber grating (28), disposed between the layers (14, 16). The layers (10-20) comprise filaments (22) and resin (24) which have different thermal expansion coefficients and the filaments (22) are oriented so as to create unequal transverse residual stresses that act through the geometry of a resin-rich region that surrounds on the grating (28) in the fiber (21). The unequal transverse residual stresses cause birefringence in the grating (28), thereby causing the grating (28) to reflect light (32) having two wavelengths with a predetermined separation, each along a different polarization axis. The wavelength separation and average wavelength between such separation have different sensitivities to temperature and strain, thereby allowing independent temperature and strain measurements using only a single grating. The birefringence is maximized when the filaments (22) of the adjacent layers (10, 12) are oriented at 90 degrees with respect to the longitudinal (Z-axis) of the fiber (21).

Wavelength dependence of the phase retardation of a quarter-wave plate

Abstract: We describe an optical heterodyne polarization interferometer that can be efficiently used for the precision measurement of the change in the state of polarization of a light wave induced by polarizing optical devices. This technique is used to measure the change with wavelength of the phase retardation of a quarter-wave plate. A theoretical derivation is presented to permit computation of the wavelength dependence of the phase shift induced by a quarter-wave plate.

A method for the determination of three-dimensional velocity fields from holographic images

Abstract: A simple general method is reported for particle tracking and velocity field determination from the reconstruction of holographic images. A preliminary experimental application is reported.

Capteur optique integre pouvant mesurer les contraintes et la temperature a l'aide d'un seul reseau de diffraction

Abstract: Un capteur optique integre presente une pluralite de couches (10-20), et une fibre optique dotee d'un reseau de fibre (28) et prevue entre les couches (14-16). Les couches (10-20) sont constituees de filaments (22) et de resine (24) presentant des coefficients de dilatation thermique differents, les filaments etant orientes de sorte que des efforts residuels transversaux inegaux agissant a travers la geometrie d'une region riche en resine entourant le reseau (28) dans la fibre (21) soient crees. Les efforts residuels transversaux inegaux provoquent une birefringence dans le reseau (28), lequel reflechit alors de la lumiere (32) a deux longueurs d'onde a separation predeterminee, chacune le long d'un axe de polarisation different. La separation des longueurs d'onde et la longueur d'onde moyenne de chaque cote de ladite separation presentent des sensibilites differentes a la temperature et aux contraintes, ce qui permet une mesure separee de la temperature et des contraintes au moyen d'un seul reseau. La birefringence est maximisee lorsque les filaments (22) des couches adjacentes (10, 12) sont orientes a 90° par rapport a l'axe longitudinal (axe des Z) de la fibre (21).