Abstract
A fibre optic Fabry-Perot sensing structure based on suspended-core fibre is presented. The interferometric structure is formed when a small length of suspended-core fibre with three or four holes is spliced to the end of a standard single mode fibre. The sensing structure is implemented firstly for strain and temperature measurement, and secondly for refractive index measurement. The interrogation of the sensing structure is obtained for the first implementation by the wavelength variation, and for the second implementation through the fringe visibility and through the analysis of the fast Fourier transform. © 2009 SPIE.

Abstract
A fiber-optic sensor for torsion measurement, based on a two-LP-mode operation in ultra high birefringent photonic crystal fiber (PCF) is described. The structure of the photonic crystal fiber presents two large asymmetric holes adjacent to the core fiber. When linearly polarized light is injected in x or in y directions, respectively, two different interferometers can be obtained. In one of these cases, as torsion is applied to the ultra Hi-Bi PCF a beat between the two interferometers is formed due to the simultaneous excitation of the two polarization states. The detection technique to read the torsion sensor is based on the analysis of the Fast Fourier Transform (FFT), which is an alternative and simple solution. The sensor exhibited reduced sensitivity to temperature and also to strain. © 2009 SPIE.

Abstract
This presentation gives a review of the main concepts behind fibre optic sensing networks. Some important application areas are mentioned, such as the monitoring of oil fields, of large Civil Engineering structures, as well as of natural environments. Then, it will be addressed the potential relevance of this technology in domains of increasingly social importance, such as Health and Elderly Care, particularly in the development of Personal Health Systems.

Abstract
An optical refractometer based on a birefringent (Hi-Bi) fiber Bragg grating (FBG) written in a new H-shaped fiber structure is proposed. This structure is formed by opening the two holes of a side-hole fiber using chemical etching. When the Hi-Bi FBG is immersed in different liquids, different responses of the slow and fast wavelengths are obtained. The refractometer is also capable of simultaneous measurement of refractive index and temperature. (c) 2008 Optical Society of America OCIS codes: 060.2310, 060.3735, 060.2370.

Abstract
A Fabry-Perot refractometer based on the suspended core fibre is presented. The Fabry-Perot cavities are formed by a section of suspended core fibre between conventional single-mode fibres. This miniature refractive tip sensor is demonstrated for the measurement of the refractive index change by measuring the fringe visibility and through the analysis of the fast Fourier transform. The two methods are compared. The temperature dependence was also characterized. [DOI: 10.2971/jeos.2009.09041]

Abstract
In this paper, it is presented a brief review of the sensing applications using suspended core fibres. Since the first publication, several authors have studied their properties and possible applications in engineering. Due to their geometry, the great potential in optical sensing is in bio and gas sensing. Recently, with the possibility of inscribing Bragg grating structures on these fibres, it is possible to use them for other applications. Finally, this paper reviews the recent works with suspended core fibres for interferometry.