Abstract
In this work, a phase-shifted fiber Bragg grating is proposed for strain sensing at extreme temperatures. The grating structure is written in bare standard single mode fiber, using the point-by-point femtosecond laser technique. Strain measurements are performed at temperatures ranging from room temperature up to 900°C. By subjecting the sensor to such extreme conditions, the wavelength of the grating increases. © 2014 OSA.

Abstract
The possibility of using polymer fiber as a refractive index sensor is presented. The sensor is based on a Fabry-Perot interferometer formed at the tip of the polymer fiber. The interference is granted due to reflections between a fiber Bragg grating and the fiber end-face. The sensor was characterized to refractive index changes at constant temperature using a fast Fourier transform analysis of the interference signal. A sensitivity of -1.94 RIU-1 was achieved with a resolution of 1 x 10(-3) RIU and a cross sensitivity to temperature of 1 x 10(-4) RIU/degrees C

Abstract
Optical fibre Bragg grating (FBG) sensors are now quite established and widely used in strain measurements in composites. However, insufficient understanding of the limitations of the embedment and measuring techniques often leads to inaccurate results. This work is a continuation of a novel method to improve the reliability and accuracy of the strain measurements on unidirectional composites using embedded FBG sensors [1]. A new combination of the pair host material/sensor was studied and characterized. Test specimens were manufactured with longitudinally embedded FBG sensors, using a glass/epoxy prepreg system, in order to compare with a carbon/epoxy prepreg system. The combined behaviour of the sensors and the host material was characterized and a procedure to obtain a more accurate strain was defined for this new chosen material.

Abstract
A Fabry-Perot interferometer based on an array of soda-lime glass microspheres is proposed for temperature sensing. The microspheres are introduced in a hollow-core silica tube using a tapered fiber tip. After the insertion of each microsphere the sensor is subjected to temperature measurements. The sensor exhibits non-linear behavior and a dependence on the number of microspheres is observed. A maximum sensitivity of 11.13 pm/degrees C is achieved, when there is only one microsphere inside the capillary structure.

Abstract
In this work a numerical model related to an optical inclinometer is presented. This model is based on a fused fiber taper monitored in the transmitted power. Comparisons are made between the numerical and experimental results and it is demonstrated good agreement with them. Thus, the model is proven to be suitable to simulate variation of parameters in order to obtain better performance of the sensor response. The numerical results demonstrate that is possible to enhance the inclinometer sensitivity by varying the legnth and waist of the taper. It is obtained a sensitivity of about 0,7 dB/degree using a taper length and waist of 1200 mu m and 30 mu m, respectively, at an angular range of 35 to 45 degrees.

Abstract
A smart material using fibre Bragg gratings (FBGs) embedded into carbon fibre-reinforced polymer for simultaneous measurement of physical parameters was designed, tested, and validated. Two FBGs were embedded in different sections of the composite sample, one fully unidirectional and the other bidirectional, which produced different sensitivities for each FBG sensor. The composite structure was characterized for strain/temperature and curvature/temperature measurements. The experimental results were compared with and agreed with finite element simulations.