Abstract
A fiber-sensing scheme with controlled sensitivity comprising a fiber Bragg grating (FBG) and a mechanically induced long-period fiber grating (MLPFG) is presented. The FBG was written by exposing the fiber to 248-nm UV laser radiation such that the Bragg wavelength is localized on the slope of a resonant band of a mechanical grating, which was produced by winding a nylon string around a fiber/grooved tube set. The strength of that resonant band was altered by applying loads to the MLPFG. For different loads, the FBG was submitted to strain values of up to 2200 mu epsilon, in steps of 200 mu epsilon, during which the Bragg wavelength and the respective transmitted peak power through the MLPFG were recorded. It was demonstrated that by applying a weight with a value of 0.78 kg to the MLPFG, the sensitivity of the FBG interrogation technique to strain variations increased from 2.23 (without load) to 3.20 pW/mu epsilon.

Abstract
We have investigated the polarization properties of long-period fibre gratings fabricated using the electric arc technique. It was found that the choice of the fabrication parameters (electric current, arc duration and pulling tension) affects the polarization dependent loss of the produced gratings. In particular, a non-monotonic dependence on the external pulling tension was obtained.

Abstract
The underlying formation mechanisms and the properties of long-period gratings produced through arc discharges are intrinsically related to the temperature reached by the fibre during arc exposure. In this work, the determination of the fibre temperature was based on Plank's blackbody radiation law. The radiation emitted by the optical fibre during heating due to an electric arc discharge, detected using a Cronin spectrometer, was fitted to the emission spectrum of the blackbody radiation, allowing the estimation of the temperature range attained by the fibre. A peak temperature of 1400 +/- 50 degrees C was obtained.

Abstract
We have investigated the sensitivity of arc-induced long-period gratings to changes of ambient refractive index. Two pure-silica-core fibres with different cladding diameters and a standard fibre were used in this study. For a 6 x 10(-3) change of the refractive index, a 240 pm shift of the resonant wavelength was achieved with long-period gratings written in the 125 mu m cladding diameter pure-silica-core fibre.

Abstract
The accompanying of civil infrastructures behavior during their whole life cycle is growing within the last few years. This fact is due to several problems detected in such structures, which is the main reason for the dispended budget by owners in their maintenance, being even higher than other costs. In another way, traditional surveillance techniques, although important are expensive, slow in time and subjective. Considering such panorama, within a national research project - SMARTE project - a new technique for management and maintenance of structures was developed and implemented in a real structure, a pre-stressed concrete bridge (Sorraia River Bridge). The developed technique, long term structural health monitoring, has as a final purpose the execution of structural maintenance in an objective and efficient way. The evaluation of the structural behavior during whole life cycle is performed in an "on line" continuous way, allowing the on time detection of existent damages. Civil infrastructures health monitoring should have the potential for the on time detection of possible anomalies or critical situations, diminishing costs related to inspections and simultaneously growing structural and users' security. Inserted in a research project - SMARTE project - a new surveillance technique for the prevention and support of civil infrastructures maintenance and management was applied into a real prototype structure - Sorraia River Bridge (Perdigão et al. 2004). The developed long term structural health monitoring is composed by a sensory, a data acquisition, a communication, a data processing and archiving and damage detection and modelling system (Figueiras et al. 2004, Matos et al. 2005). Figure 1 presents a simple and illustrative scheme of it. SMARTE project has two main objectives. The first one is related to the installation of the sensory system in the bridge, during it execution phase, which should be liable and robust. In Fig. 2 it is possible to observe the used cantilever constructive process and utilized instrumentation devices (Figueiras et al. 2004). This respective component, based on sensors that were placed in special locations according to a previously established criteria, will allow the readings and storage of most important parameters for a correct interpretation of the structure behaviour during it whole life cycle. The second main objective is related to the development of a component for data processing and archiving. Such system should translate the obtained data in more objective information that could be used as decision criteria for civil infrastructures management. In this article it is presented the SMARTE project and respective main objectives. A brief description of each system of the developed and implemented long term structural health monitoring scheme is also executed. The initially proposed objectives were achieved and new research themes appeared with this project. A new project was so initialized which aim is to continue the Sorraia River Bridge long term monitoring and to develop the previous identified investigation subjects. (Figure Presented) © 2006 Taylor & Francis Group.

Abstract
The objective of this work was to study, understand and evaluate the effect of different geometric configurations of carbon plies, in the reflected wavelength spectrum of Bragg grating structure together with the effect of the recoating process of the sensor. The different possibilities depend upon the orientation and location of the optical fibre relative to the composite reinforcement orientation and the presence/absence of recoating. The material stacking sequence and the cure conditions were are also studied and the influence of the different possibilities was considered. The optical spectrum response obtained by the interaction of the optical fibre with the host material is shown.