Abstract
An all fibre Mach-Zehnder interferometric configuration based on a suspended twin-core fibre is described. Due to the birefringence of the fibre cores, two interferometers were obtained by illuminating the fibre with polarized light. Applying strain, curvature and temperature to the sensing head, different sensitivities were observed, which permits the use of the matrix method to discriminate these three measurands.

Abstract
In this work it is presented a novel in-fibre modal interferometer based on a non-adiabatic biconical fused taper that couples light between the cladding and the core, combined with the Fresnel reflection at the fibre end. It is observed that the returned liaht from this fibre structure shows a channelled spectrum similar to that of a two-wave Michelson interferometer. The application of this device as a fibre optic flowmeter sensor is demonstrated.

Abstract
Fibre optic modal interferometry has been around for long as a sensing concept. Initially mainly supported on the utilization of standard Hi-Bi fibres associated to polarimetric modal interferometry, later this sensing approach evolved to modal interference based on spatial modes propagating in the core, and on spatial modes propagating in the core and in the cladding, with coupling performed by fibre devices such as long period gratings and tapers. More recently the outcome of Photonic Crystal Fibres (PCF) originated a burst of activity around the concept of modal interferometry for sensing. The reasons for that viewed in a historic perspective are presented in this work.

Abstract
In this work, a multiwavelength Raman fiber laser based on a highly birefringent photonic crystal fiber is presented. A laser resonator is formed when the Raman amplification with cooperative Rayleigh scattering in a dispersion compensating fiber is used as a distributed mirror and combined with a highly birefringent photonic crystal fiber loop mirror. The multiwavelength Raman fiber laser presents 11 stable channels per nm with a peak power of similar to 1.5mW. Stable multiwavelength lasing at room temperature is achieved due to the low sensitivity to temperature and environmental noise of the highly birefringent photonic crystal fiber based fiber loop mirror.

Abstract
An inclinometer sensor based on optical fibre-taper-modal Michelson interferometer is demonstrated. The magnitude of the tilt (bending angle of the fibre taper interferometer) is obtained by passive interferometric interrogation based on the generation of two quadrature phase-shifted signals from two fibre Bragg gratings. Optical phase-to-rotation sensitivity of 1.13 rad/degree with a 14 mrad/root Hz resolution is achieved.

Abstract
In this study an optic fibre system for health monitoring of fibre reinforced plastics was developed. It is based on the detection of acoustic emission (AE) waves in a loaded material. A low-finesse Fabry-Perot interferometer sensor is used as alternative to the conventional piezoelectric transducers for AE waves sensing. An original procedure for optical fibre sensor interrogation is proposed.