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.

Abstract
An optical fibre sensor for simultaneous measurement of refractive index and temperature is presented. The refractive index measurement is based on the visibility variations of a Fabry- Perot interferometer with interfering waves generated in a low reflectivity Bragg grating inscribed on a Panda fibre and in the fibre tip (Fresnel reflection) in contact with the liquid. The temperature measurement is based on the wavelength shift of the FBG peaks. Results obtained show the feasibility of simultaneous measurement of refractive index and temperature and also the possibility of adjusting fringe visibility via polarization control.

Abstract
A novel fiber optic curvature sensor based on a core-offset single-mode fiber (SMF) and on a fiber Bragg grating (FBG) is presented. The FBG cladding modes are efficiently excited by the large core misalignment. The curvature of the beam can be obtained by the reflected power of the core mode and the recoupled cladding mode.

Abstract
In this work, we present a fiber Bragg grating interrogation based on high-birefringence fiber loop mirror for strain-temperature discrimination. Due to spectral response of the optical filters it is possible to determine the variation of the wavelength and the optical power of the Bragg grating sensor when subject to strain or temperature. Maximum errors of +/- 0.4 degrees C and 12 mu epsilon are reported over 80 degrees C and 2000 mu epsilon measurement ranges. (c) 2006 Wiley Periodicals, Inc.

Abstract
An optical current sensor based on a metal coated Hi-Bi fiber loop mirror is reported. This current sensor quantifies the current through the measurement of the temperature which varies accordingly with the magnitude of the electrical current. The temperature change is analyzed through the variation of the wavelength shift of a fringe minimum of a Hi-Bi fiber loop mirror. The minimum current detection was found to be approximately 10 A. (c) 2008 Wiley Periodicals, Inc.

Abstract
In the present paper, the influence of the fiber Bragg grating (FBG) length and its coating on embedded FBGs in polymers is evaluated. Different FBG lengths and coatings, uncoated and acrylate-recoated, are used. The evolution of their spectra is also followed during laminate curing on a hot-plate press. The Bragg gratings are used as optical fiber sensors, and their sensitivity and reliability are analyzed. The resulting sensor signal characteristics and the strain answers to different loading modes, i.e. tensile, flexural and through-thickness compression, are also studied.