Abstract
In this work, two all-fibre interferometric configurations based on suspended core fibres (SCF) are investigated. A Fabry-Perot cavity made of SCF spliced in-between segments of single-mode and hollow-core fiber is proposed. An alternative sensing head configuration formed by the insertion of a length of SCF as a birefringence element in a Sagnac interferometer is also demonstrated. The sensitivity to pressure and temperature was determined for both configurations.

Abstract
In this work it is investigated the strain and temperature sensing characteristics of modal interferometers supported by two Bragg fibers with different cross-section cladding geometries. It is shown that the sensitivity to these measurands is different for the two fibers, which turns feasible the conception of several sensing configurations based on the combination of these two fiber types for simultaneous measurement of strain and temperature.

Abstract
This work describes a fibre optic sensing structure that is sensitive to curvature, and features a low temperature- and strain cross-sensitivity. It is based on multimode interference, and relies on a single mode - step index multimode - single mode fibre configuration. It was observed that the transmitted optical power in such layout becomes highly sensitive to the wavelength of operation and to the length of the multimode fibre. The optical spectrum entertains two dominant loss bands, at wavelengths that have similar responses both to temperature and strain, and different responses to curvature. Based on this result, an interrogation approach is proposed that permits substantial sensitivity to curvature (8.7 +/- 0.1 nm.m) and residual sensitivities to temperature and strain (0.3 +/- 0.1 pm/degrees C and -0.06 +/- 0.01 pm/mu epsilon, respectively).

Abstract
In this work the concept of long period based optical fibre sensors with the broadband light illumination generated just after the sensing structure is presented. This new approach allows the interrogation in transmission of the sensing head while integrated in a reflective configuration, which means the LPG sensor is seen in transmission by the optical source but in reflection by the measurement system. Also, it is shown that with this illumination layout the optical power balance is more favorable when compared with the standard configurations, allowing better sensor performances particularly when the sensing head is located far away from the photodetection and processing unit. This is demonstrated for the case of the LPG structure applied to measure strain and using ratiometric interrogation based on the readout of the optical power reflected by two fibre Bragg gratings spectrally located in each side of the LPG resonance.

Abstract
The interrogation of a suspended-core Fabry-Perot interferometric cavity through the illumination of a dual wavelength Raman fiber laser is reported. The proposed scheme is based on the use of a dual wavelength source for the generation of two quadrature phase-shifted signals that allows the recovery of the temperature change. The dual wavelength Raman fiber laser is based on fiber Bragg gratings combined with a virtual mirror. The use of this source allows a passive and accurate interrogation of the temperature variation, while taking advantage of the Rayleigh scattering growth as a virtual mirror in the laser.

Abstract
It is shown how the design possibilities offered by double-layer uniform-waist tapered optical fibers (DLUWTs) permit to move the wavelength detection range to adapt the response of the sensors to varied conditions. In particular, we have obtained very good experimental curves showing that we can achieve plasmon resonances in the C-band of the optical communications, around 1.5 mu m, for the range of refractive indices of aqueous media, highly interesting in the biosensors field. Also, we show results for other interesting wavelength region, around 500 nm, where we can take advantage of the absorption peaks of the analytes. Finally, we explore the possibilities of using InN as a dielectric material for the second layer of the deposition. These results contribute to considerably expand the applicability and performance of SPR fiber sensors.