Abstract
A fibre Bragg grating structure arranged in a twisted configuration is proposed for sensing applications. The characteristics of the sensing head for measuring temperature, longitudinal strain and transverse load are analysed. It is shown that this configuration is particularly applicable for transverse load measurement. In this case a resolution of 0.002 N mm(-1)Hz(-1/2) was achieved.

Abstract
This work describes a fiber optic sensing structure that is sensitive to curvature, and features a low temperature-and strain cross-sensitivity. It is based on multimode interference, and relies on a singlemode-step index multimode-singlemode fiber structure. It was observed that the transmitted optical power in such a layout is highly sensitive to the wavelength of operation, and to the length of the multimode fiber. The optical spectrum exhibits two dominant loss bands, at wavelengths that have similar responses both to temperature and strain, but different responses to curvature. Based on this result, an interrogation approach is proposed that permits substantial sensitivity to curvature (8.7 +/- 0.1 nm m) and residual sensitivities to temperature and strain (0.3 +/- 0.1 pm degrees C(-1) and (-0.06 +/- 0.01) x 10(-6) m m(-1), respectively). The beam-propagation method was employed for modeling the propagation of light along the optical fiber sensing device proposed.

Abstract
A robust all-fibre interferometric interrogation technique based on the wavelength modulation of a pi-shifted fibre Bragg grating is proposed. The concept is demonstrated for strain measurement using a Bragg-grating-based Fabry-Perot interferometer. The strain-phase relationship is shown to be linear with a sensitivity slope of (2.19 +/- 0.02)degrees/mu epsilon. A strain resolution of approximate to 2.4 mu e is demonstrated.

Abstract
The paper presents the application of temperature acquisition systems integrating thermocouples, a thermographic camera and fibre Bragg grating (FBG) sensors in gas metal arc welding (GMAW) process, MIG ( metal inert gas) welding type. Efficient procedures to use FBG sensors and thermocouples were developed. The paper presents and compares measurements made in welded plates of aluminium alloy 6082-T6. Tests were performed in both plate surfaces and good agreement between the three techniques was found.

Abstract
This work shows the changes of bending curvature sensitivity when the same long- period fibre grating has different phase shifts. From the knowledge that the coupling constant is reduced as curvature increases, we theoretically and experimentally assess the possibility that the bend sensitivity follows the grating spectrum evolution during the point- to-point fabrication technique. We also show that control of bend sensitivity can be applied to the simultaneous measurement of bend and temperature.

Abstract
We used a pair of Bragg gratings written in high birefringence fibre optics to measure, simultaneously, longitudinal and transverse strain and temperature. The Bragg gratings are superimposed in the same position of the fibre optic, so as to behave as a punctual sensor. The sensitivity of the spectral response of the device to longitudinal strain, transverse strain and temperature are all characterized, and the results of its application as a three-parameter sensor are also presented.