Abstract
A single-mode non-adiabatic tapered optical fiber (NATOF) sensor was inserted into a Sagnac loop interferometer allowing tuning its sensitivity to refractive index (RI) by use of polarization control. By adjusting any polarization controllers inserted in the Sagnac loop interferometer, various cladding modes are selectively excited in each arm of the interferometric taper resulting into different phase changes for the clockwise and counterclockwise beams. By this method, sensitivity of the sensor for RI in the range from 1.3380 to 1.3510 was tuned between 876.24 RIU/nm to 1233.07 RIU/nm.

Abstract
A technique for the fabrication of luminescence based fiber optic optrodes with multiple analyte sensitivity is proposed. Combination of photosensitive polymers doped with different luminescent indicators was used to produce fiber probes, by self-guiding photopolymerization, having different geometries and sensing capabilities. Results demonstrating the method flexibility are shown with luminescent probes doped with CdSe/ZnS quantum dots and an organometalic ruthenium complex for simultaneous detection of oxygen and temperature.

Abstract
The implementation of refractometric based fiber optic sensors for environmental monitoring is discussed. Several sensing head configurations and interrogation schemes are presented and compared in the framework of different biochemical sensing applications. Results are presented demonstrating the suitability of this technology to monitor a diversity of chemical and biological parameters of environmental significance.

Abstract
This work describes the implementation of an optical fiber interferometric system for differential thermal analysis. The system is based on a white light Mach-Zehnder configuration, with serrodyne phase modulation, to interrogate two identical fiber Bragg gratings (FBG) in a differential scheme. Operation and signal processing with low cost digital instrumentation developed in Labview environment enabled FBG temperature measurement with a +/- 0.012 degrees C resolution nearly matching the performance of standard hardware. Preliminary results were obtained, where mixed samples of acetone and methanol could be successfully identified, indicating the suitability of the system for high accuracy differential thermal analysis using low cost instrumentation.

Abstract
A fiber optic FBG cladding modes based sensor, for simultaneous measurement of strain and temperature is presented. The FBG cladding modes are efficiently excited by the large core misalignment. This technique enables the possibility to readout simultaneously in reflection the cladding mode (lambda(cl)) and the core mode (lambda(co)). lambda(cl), lambda(co) depend on strain and temperature and show different sensibilities for each parameter, enabling their discrimination. The experimental result shows a good performance in terms of linearity and sensitivity.

Abstract
An optical fibre sensor for determination of acetic acid is presented. The sensing probe is based on a fiber Bragg grating (FBG) Fabry-Perot cavity, coated with a thin film of sol-gel-PVP (polyVynil Pirrolidone) composite material. The polymeric thin film renders interferometric output sensitive to the presence of carboxylic acid species. Results show that the wavelength of the interferometric peaks change with acetic acid concentration, enabling its quantification. Coupling the fibre probe with a serrodyne modulated readout interferometer enables pseudo-heterodyne interrogation and the detection of acetic acid with a sensitivity of 1 deg/0.01% and a resolution of 0.2% v/v. The results demonstrate the potential of the proposed scheme to operate as a sensitive chemical sensor platform. © 2009 SPIE.