Abstract
An intensity curvature sensor using a Photonic Crystal Fiber (PCF) with three coupled cores is proposed. The three cores were aligned and there was an air hole between each two consecutive cores. The fiber had a low air filling fraction, which means that the cores remain coupled in the wavelength region studied. Due to this coupling, interference is obtained in the fiber output even if just a single core is illuminated. A configuration using reflection interrogation, which used a section fiber with 0.13 m as the sensing head, was characterized for curvature sensing. When the fiber is bended along the plane of the cores, one of the lateral cores will be stretched and the other compressed. This changes the coupling coefficient between the three cores, changing the output optical power intensity. The sensitivity of the sensing head was strongly dependent on the direction of bending, having its maximum when the bending direction was along the plane of the cores. A maximum curvature sensitivity of 2.0 dB/m(-1) was demonstrated between 0 m and 2.8 m.

Abstract
The synthesis of carbon nanoparticles obtained by direct laser ablation [UV pulsed laser irradiation (248 nm, KrF)] of carbon targets immersed in water is described. Laser ablation features were optimized to produce carbon nanoparticles with dimensions up to about 100 nm. After functionalization with NH2-polyethylene-glycol (PEG(200)) and N-acetyl-L-cysteine (NAC) the carbon nanoparticles become fluorescent with excitation and emission wavelengths at 340 and 450 nm, respectively. The fluorescence decay time was complex and a three-component decay time model originated a good fit (chi = 1.09) with the following lifetimes: tau(1) = 0.35 ns; tau(2) = 1.8 ns; and tau(3) = 4.39 ns. The fluorescence of the carbon dots is sensitive to pH with an apparent PKa = 4.2. The carbon dots were characterized by H-1 NMR and HSQC and the results show an interaction between PEG(200) and the carbon surface as well as a dependence of the chemical shift with the reaction time. The fluorescence intensity of the nanoparticles is quenched by the presence of Hg(II) and Cu(II) ions with a Stern-Volmer constant (pH = 6.8) of 1.3 x 10(5) and 5.6 x 10(4) M-1, respectively. As such the synthesis and application of a novel biocompatible nanosensor for measuring Hg(II) is presented.

Abstract
In the recent years, sol-gel films have been intensively used in optical sensors configurations. Due to its hydrophobic nature, ormosil films have been reported to be a promising supporting matrix for oxygen sensing dyes for measurements in aqueous media. In this work, the impact of the sol-gel host fabrication parameters in the characteristics of the resulting oxygen sensing membranes is thoroughly evaluated. Different combinations of organic-inorganic precursors, with different aging times, were tested as oxygen sensors. All the solution were doped with ruthenium complex Ru(II)-tris(4,7-diphenyl-1,10- phenanthroline) to introduce oxygen sensitivity. Thin films were produced by dip coating of glass slides. The oxygen sensitive films were tested in aqueous phase in equilibrium with different oxygen gas compositions, using a phase-modulation technique. Sensor performance parameters such as Stern-Volmer constant, quenching efficiency and lifetime response are reported. The data obtained clearly indicates that increased aging times and longer organic groups produce sensors with the highest sensitivity to dissolved oxygen. From all sol-gel films produced, the BTEOS:TEOS (1:1) mixture is the most promising for sensor construction. © (2010) Trans Tech Publications.

Abstract
The proposed sensing device relies on the self-imaging effect that occurs in a pure silica multimode fiber (coreless MMF) section of a single-mode-multimode-single-mode (SMS)-based fiber structure. The influence of the coreless-MMF diameter on the external refractive index (RI) variation permitted the sensing head with the lowest MMF diameter (i.e., 55 mu m) to exhibit the maximum sensitivity (2800 nm/RIU). This approach also implied an ultrahigh sensitivity of this fiber device to temperature variations in the liquid RI of 1.43: a maximum sensitivity of -1880 pm/degrees C was indeed attained. Therefore, the results produced were over 100-fold those of the typical value of approximately 13 pm/degrees C achieved in air using a similar device. Numerical analysis of an evanescent wave absorption sensor was performed, in order to extend the range of liquids with a detectable RI to above 1.43. The suggested model is an SMS fiber device where a polymer coating, with an RI as low as 1.3, is deposited over the coreless MMF; numerical results are presented pertaining to several polymer thicknesses in terms of external RI variation. (C) 2012 Optical Society of America

Abstract
In this paper an optofluidic chip for simultaneous determination of refractive index and acquisition of absorption or fluorescent spectra is described. The system comprises a microfluidic channel with multiple inlet/outlet for sample handling and a dual fiber optic probe, standing face to face across the channel, for the optical measurements. An FBG based Fabry Perot cavity, and a Braggmeter, allow for interferometric measurement of the refractive index while external illumination and a multimode fiber enable acquisition of the absorption/fluorescence spectra with a CCD spectrometer. Preliminary results showing the viability of simultaneous measurement are obtained from the characterization of mixed samples with distinct refractive index and dye concentrations.

Abstract
In this work a magnetic field sensor based on an FBG coated with a thin film of Terfenol-D is presented. The sensor was tested with two optical interrogation systems: one, a scanning laser system with a 1 pm resolution, and the other a differential white light interferometer (WLI). The results obtained in the magnetic field range of 20 mT to 100 mT, show the possibility of increasing the magnetic field measurement resolution, with temperature fluctuations invariance, by a factor of 4.5 when using the WLI system.