Abstract
In this work, sensitivity to strain, temperature and curvature of a sensor relying on modal interferometry in hollow-core photonic crystal fibre is studied. The sensing structure is simply a piece of hollow-core fibre connected in both ends to standard single mode fibre. An interference pattern that is associated to the interference of the light that propagates in the hollow core fundamental mode with light that propagates in other modes is observed. The phase of this interference pattern changes with the measurand interaction, which is the basis for considering this structure for sensing. The phase recovery is performed using a white light interferometric technique. © 2009 SPIE.

Abstract
A new interrogation method based on Fibre Bragg Gratings (FBG) for Surface Plamon Resonance (SPR) sensors in the region of refractive indices of aqueous solutions is described. Two FBGs are selected with their Bragg wavelengths at opposite sides of the plasmon resonance peak. The response of the system can be made independent of the fluctuations of the optical power source, and the linearity and the sensitivity of the sensor are improved. The use of the spectral selectivity of gratings for the interrogation of SPR sensors in different configurations is also promising in terms of multiplexing, temperature referencing or multiparameter detection. © 2009 SPIE.

Abstract
We present and demonstrate a high-resolution absolute-distance measurement system based on multiple-wavelength interferometry. The information on a cavity length is obtained by sampling a fringe of its spectral response at different wavelengths. This is achieved by simultaneously tuning multiple fiber Bragg gratings. For a two wavelength system, an unambiguous measurement range of 262 µm was obtained with a resolution of 14.3 nm.

Abstract
An all fiber interrogation technique for Bragg sensors is presented. It is based on generation of an electric carrier by modulating the coupling length of a wavelength division multiplexer. Results are given when both serrodyne and sinusoidal modulation formats are considered.

Abstract
An all fiber technique for interrogation of interferometric low-finesse Fabry-Perot cavities is presented. It is based on the modulation of the spectral transfer function of a wavelength division multiplexer. Results are given when both serrodyne and sinusoidal modulation formats are considered.

Abstract
A sensor based on a Sagnac topology in reflection is described. The sensor uses the properties of its frequency response in order to obtain a self-referenced signal proportional to the measured signal. The sensor is a versatile structure for the monitoring of static and dynamic physical parameters, which require a small number of optical components and simple signal processing.