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 work a fiber optic interferometric system for differential refractive index measurement is described. The system is based on a white light Mach-Zehnder configuration, with serrodyne phase modulation, to interrogate two similar non-adiabatic tapered optical fiber sensors in a differential scheme. In this situation it is possible to measure the refractive index independent of temperature. Signal processing with low cost digital instrumentation developed in Labview environment allows a detectable change in refractive index of Delta n approximate to 2x10(-6), which is, from the best of our knowledge the highest resolution achieved using a fiber taper device. The results demonstrate the potential of the proposed scheme to operate as chemical and biological sensing platform.

Abstract
A fiber optic sensor for simultaneous measurement of refractive index and temperature is presented. The sensing probe is achieved by introducing multimode interference inside a high birefringence fiber loop mirror resulting in a configuration capable of refractive index and temperature discrimination. The multimode interference peak is sensitive to the surrounding refractive index (90 nm/RIU) and slightly responsive to the temperature (0.005 nm/degrees C). On the other hand, the birrefringent fiber loop mirror is highly sensitive to temperature (2.39 nm/degrees C) and has no response to refractive index. Therefore, a temperature independent refractive index measurement can be made with a resolution of +/- 2.5x10(-5).

Abstract
In this work a novel optical-fiber sensor for carbon dioxide measurement is presented. A polymeric sensitive layer based on the acid-base equilibrium of phenol and of its derivative 4-nitro-phenol is used for carbon dioxide determination. The sensitive material presents changes in color and in its refractive index. Colorimetric and refractometric measurements were performed. The results show the sensor is more sensitive for lower concentrations and a saturation effect occurs for higher levels. For the colorimetric response, a resolution of +/- 0.15% was estimated and a response time of 30s was measured. For the refractometric measurements, a resolution of +/- 0.50% could be estimated and a response time of 12s was measured. Reversibility and reproducibility were also demonstrated.

Abstract
An indicator free optical fiber sensor for determination of carbon dioxide is presented. The sensing layer is based on the acid-basic equilibrium of phenol and of its derivative p-nitro-phenol that, in the presence of CO2, are prone to protonation introducing refractive index changes. The new sensitive layer is characterized and tested in different refractometric fiber optic sensor configurations. Using a fiber based interferometric setup, a CO 2 dependent refractive index change of ~0.05 RIU is observed, in the 10%-90% CO2 concentration range, demonstrating the membrane viability. Preliminary results are presented for an all-fiber LPG-based carbon dioxide sensor.

Abstract
The intrinsic advantages of optical sensor technology are very appealing for high voltage applications and can become a valuable asset in a new generation of smart grids. In this paper the authors present a review of optical sensors technologies for electrical current metering in high voltage applications. A brief historical overview is given together with a more detailed focus on recent developments. Technologies addressed include all fiber sensors, bulk magneto-optical sensors, piezoelectric transducers, magnetic force sensors and hybrid sensors. The physical principles and main advantages and disadvantages are discussed. Configurations and strategies to overcome common problems, such as interference from external currents and magnetic fields induced linear birefringence and others are discussed. The state-of-the-art is presented including commercial available systems.