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
The major achievements in the field of optical sensors in the past two decades have remained mostly limited to the laboratory demonstrations. There are very few examples of optical sensors, which have been reduced to practice, and have established themselves in major markets. The main bottleneck in this field is the issue of manufacturability. In this paper we present optical sensors based on slotted multimode interference waveguides. We show that the sensitivity increases proportionally to the number of slots. The sensor can be tuned to highest sensitivity in the refractive index ranges necessary to detect protein-based molecules or other water-soluble chemical or biological materials. The material of choice is a sol-gel (ORMOCER) matrix that after completion of the process becomes mostly glass and it is highly stable. Sensors made with this technology are suited to high volume manufacturing.

Abstract
An all-optical scheme for simultaneous determination of oxygen and temperature is presented. A ruthenium complex immobilized in a non-hydrolytic sol-gel matrix is used as oxygen sensor. Temperature information is provided by CdSe quantum dots immobilized in the same material. While the dye luminescence is quenched by oxygen and temperature, the nanocrystals luminescence depends only on temperature. Results presented demonstrate that the combined luminescence response allows to simultaneously assess both parameters using a single optical fiber system.

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.