Abstract
This paper presents a smart composite for structural monitorisation, based on fibre Bragg grating sensors. The sensor plate, a carbon fibre reinforced plastic laminate having an embedded optical strain gauge rosette, was designed, produced, and tested. These instrumented carbon fibre laminates can be used for monitoring of reinforcement and protection of structures, playing an important role in the control of repaired constructions. The smart structures developed are shown to have the ability of measuring temperature and strain.

Abstract
We have flattened the gain spectrum of a commercial Erbium-doped fibre amplifier, obtaining a curve with approximately 3 dB of ripple, from 1524 nm to 1551 nm, using long-period fibre gratings as equalising optical filters. The fabrication principle of the long-period fibre grating is based on the electric arc technique.

Abstract

Abstract
We report, for the first time to our knowledge, the excellent optical performance of long-period gratings written in three standard libers and in two nonstandard fibers, namely, S-doped and N-doped fibers, using the flexible and low-cost electric are technique. The fundamental mechanism for their formation is proposed. The gratings thermal behavior and the effect of fiber preannealing prior to writing have been investigated. We have demonstrated a good stability of these gratings at high temperatures.

Abstract
We propose to use nondegenerate cascaded four-wave mixing processes for efficient high order harmonic generation in plasmas and dielectrics. A simple model is used to estimate the temporal duration and maximum order of the generated harmonics for both a typical laser-produced plasma and a glass slide. In the plasma case, we expect considerable pulse compression, with the production of sub-femtosecond pulses starting from the 8th harmonic.

Abstract
A new method of high-harmonic generation by intense and short laser pulses is proposed. This method is based on the idea that, in quite general situations, a cascade of four-wave-mixing processes can occur. A theoretical model is established and exact analytic solutions are obtained. Examples of possible experiments in low-charged plasmas and in glass are discussed in detail, including the phase-matching conditions, the angular spread of the secondary beams and the pulse durations. Numerical examples of the possible generation of sub-femtosecond pulses are also given.