Abstract
A highly birefringent photonic bandgap Bragg fiber loop mirror configuration for simultaneous measurement of strain and temperature is proposed. The group birefringence and the sharp loss peaks are observable in the spectral response. Because the sensing head presents different sensitivities for strain and temperature measurands, these physical parameters can be discriminated by using the matrix method. It should be noted that this Bragg fiber presents high sensitivity to temperature, of similar to 5.75 nm/degrees C, due to the group birefringence variation. The rms deviations obtained are +/- 19.32 mu e and +/- 0.5 degrees C, for strain and temperature measurements, respectively. (C) 2011 Optical Society of America

Abstract
In this work, a laser sensor is described that uses the multipath interference produced inside a ring cavity to measure the power loss induced by a moving taper intensity sensor. The laser is created due to the virtual distributed mirror formed by the Rayleigh scattering produced in a dispersion compensating fiber when pumped by a Raman laser. Two laser peaks were formed, one of them is obtained by the Raman gain (1555 nm) inside the ring and the second is created by the combination of the Raman gain and the Rayleigh scattering (1565 nm). A taper sensor is used as displacement sensor and when the losses is applied in the taper the second laser peak is reduced and the first peak is maintained constant and can be used as reference level.

Abstract
A fiber-optic curvature sensor based on a core offset single-mode fiber (SMF) combined with a fiber Bragg grating (FBG) is presented. The FBG cladding modes are efficiently excited by the large core misalignment. The curvature of the fiber can be obtained by the ratio between the recoupled cladding mode power and the reflected core mode power. These measurements are independent from temperature variation.

Abstract
A system to interrogate optical fiber interferometric sensors with digital control is presented. The system is based on a receiving white light Mach-Zehnder interferometer and is capable of operating with four distinct synthetic and pseudo-heterodyne signal detection schemes. A differential phase detection scheme was implemented and system performance with the different processing schemes was compared using fiber Bragg grating based Fabry-Perot cavity strain sensors. With a lock-in time constant of 1 s, most digital techniques were able to nearly match the performance of a standard hardware system, demonstrating the feasibility of low-cost high-resolution interferometric systems operated with virtual instrumentation.

Abstract
A fiber-optic sensor for simultaneous measurement of refractive index and temperature is described. The refractive index measurement is based on the visibility variations of a Fabry-Perot interferometer. It is formed with the interfering waves generated from a low reflectivity Bragg grating inscribed on a Panda fiber and from the fiber end tip (Fresnel reflection) in contact with the liquid. The sensor is characterized by immersing the fiber tip in distilled water with different concentrations of ethylene glycol. A linear relation of the interferometer fringe visibility with refractive index variation is observed. The temperature is determined by the wavelength shift of the FBG peaks. Results show the feasibility of simultaneous measurement of refractive index and temperature and also the possibility of adjusting fringe visibility via polarization control.

Abstract
In this paper, we present a novel smart composite based on single mode optical fibres embedded in a hybrid composite laminated. This smart composite comprehended three optical fibres: an optical fibre positioned between two layers of carbon fibres; other optical fibre embedded in two layers of glass fibres; and another optical fibre inserted between the two different composite laminates. Due to cure process using hot plate press, different optical attenuations were obtained for the three optical fibres. The optical fibre positioned between the two different layers (carbon/glass) presented higher losses when compared with the two other optical fibres embedded between equal types of layers. The losses result from the different diameter of carbon/glass and the different coefficient of thermal expansion of the composite material. The smart composite was characterised in terms of its sensitivity to temperature and pressure, independently. Using a matrix method, it was possible to discriminate the pressure and the temperature with only one measurement. Maximum errors of 2.45 degrees C and 0.6 kN/m(2) were found to 60 degrees C and 2500 kN/m(2) measurement ranges.