Abstract
A self-referenced fibre optic intensity sensor supported by a multiple beam Sagnac configuration is investigated. Sensor linearity and sensitivity are analysed. Theoretical and experimental results are compared, being considered the sensor design and its optimisation.

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.

Abstract
The concept of time refraction is introduced to describe the effects of a sudden change of the optical properties of a dielectric medium. This can be seen as the most elementary process associated with photon acceleration and frequency upshifting. The quantum theory of such a process shows that the initial wave splits into time-transmitted and time-reflected waves propagating in opposite directions after the occurrence of a time discontinuity of the refractive index. The time refraction laws, analogous to the well known Fresnel formulas and Snell's law, are also derived. It is shown that, in quantum terms, time refraction is equivalent to a squeezing transformation.

Abstract
It is shown here that st straightforward procedure can be used to quantize the linearized equations for an electromagnetic field in a plasma. This leads to a definition of an effective mass for the transverse photons, and a different one far the longitudinal photons, or plasmons. Both masses are simply proportional to the electron plasma density. A nonlinear perturbative analysis can also be used to extend the quantization procedure, in order to include the ponderomotive force effects. This leads to the definition of a photon charge operator. The mean value of this operator, for a quantum state with a photon occupation number equal to 1, is the equivalent charge of the photon in a plasma.

Abstract

Abstract
The values of measured and calculated spectroscopic quantities of lithium niobate doped with rare earth and transition metal ions, such as polarized emission and absorption cross sections, variation of fluorescence life time with temperature and concentration of the dopant, Judd-Ofelt coefficients, non-radiative transition probabilities and energy levels are presented. Wherever published data is available, comparison with measured or calculated data presented in this work is carried out. The theories utilized in the interpretation of the experimental results, such as Judd-Ofelt theory, Fuchtbauer-Lademburg relation and McCumber theory are summarily presented.