Abstract
A fiber sensing system is presented that allows simultaneous measurement of both refractive index and temperature while providing passive referencing to intensity fluctuations. © 2006 OSA/OFS 2006.

Abstract
The measurement of micro-displacement or bending using a long-period fibre grating (LPG) in a self-referenced fibre optic intensity sensor is presented. The sensing head is based on a LPG whose attenuation peak changes as a function of its micro-displacement or bending and the fibre optic intensity sensor is referenced in frequency. Two other LPGs were used as rejection filters. located at the output of the optical source to shorten its spectral width. The implemented experimental set-up is described and, the results are presented being considered the measurement range and the intrinsic resolution.

Abstract
A quasi-distributed displacement sensor for structural monitoring using an optical time domain reflectometer is demonstrated. Four displacement sensing heads are placed along a standard single mode optical fibre in several locations with different intervals. Their configurations introduce power loss through the decrease of their fibre loop radius when displacement is applied. The decrease of the light intensity with displacement variation is reported. Losses of 9 dB for a similar to 120 mm displacement with a sensitivity of similar to 0.027 dB/mm are reported. The quasi-distributed configuration is able to address sensors with similar to 1 m distance resolution between them.

Abstract
This work presents an alternative solution for simultaneous measurement of strain and temperature. The sensing head is formed by a long-period fiber grating combined with a high-birefringence fiber loop mirror resulting in a configuration capable of temperature and strain discrimination. These optical devices have opposite sensitivity responses when a variation of temperature and/or strain is applied. Maximum errors of +/- 0.8 degrees C and +/- 21 mu epsilon are reported over 60 degrees C and 700-mu epsilon measurement ranges, respectively.

Abstract
A refractometric sensor based on a phase-shifted long-period fiber grating written by electric-arc discharges is presented. Transmission and reflective configurations for refractive index measurements are studied. It is observed that the reflective topology permits better performance compared with the transmission one, which is the approach normally utilized in the context of long-period fiber sensing. The resolution achieved in the measurement of refractive index enables the application of this sensing head structure in demanding situations, such as the measurement of the level of salinity of water. (c) 2006 Optical Society of America.

Abstract
A new concept to measure rotation angles based on a fiber-optic modal Mach-Zehnder interferometer is demonstrated by using a nonadiabatic taper cascaded with a long-period fiber grating. Information about the magnitude of the rotation angle can be obtained from the measurement of the interference pattern visibility, and under certain conditions it is also possible to obtain the sign of the rotation angle from the induced phase variation in the fiber interferometer. (c) 2006 Optical Society of America.