Abstract
Semiconductor nano-particles, or quantum dots, with their relatively high quantum yields, narrow luminescence spectrum, outstanding photostability and the ability to tune their optical properties, are ideal for biological tagging applications and a very powerful tool for chemical sensors. In this paper an overview of this rapidly expanding area of research is presented. Additionally, some results are shown, in the framework of optical oxygen sensors, which establish quantum dots as suitable temperature and intensity references for application in luminescence based chemical sensors.

Abstract
We present, for the first time to our knowledge, results on the characterization of response of a dual resonance observed in the spectrum of a single long-period grating arcinduced in a B/Ge co-doped fiber to different physical parameters. The dual resonance is formed by two overlapping resonances corresponding to coupling of the core mode to symmetric and antisymmetric cladding modes. Therefore, these resonances may behave differently when strain, bending, torsion, or temperature is applied to the grating. We show that the bending, strain, and torsion sensitivities of the two resonances are very different, while the temperature sensitivities are almost the same. © 2008 IEEE.

Abstract
A novel in-fiber modal interferometer is presented that is based on a nonadiabatic biconical fused taper that couples light between the cladding and the core, combined with the Fresnel reflection at the fiber end. It is observed that the returned light from this fiber structure shows a channeled spectrum similar to that of a two-wave Michelson interferometer. The application of this device as a fiber optic flowmeter sensor is demonstrated. 2007 (c) Optical Society of America.

Abstract
A novel Mach-Zehnder interferometer based on a fiber multimode interference structure combined with a long-period fiber grating (LPG) is proposed. The multimode interference is achieved through the use of a MMF section spliced between two single-mode fibers, with a length adjusted to couple a fraction of light into the cladding modes. A LPG placed after the MMF couples light back into the fiber core, completing the Mach-Zehnder interferometer. This novel configuration was demonstrated as a bending sensor. (c) 2007 Optical Society ofAmerica.

Abstract
A micrometric Fabry-Perot refractometer based on an end-of-fiber polymer tip is proposed. The fiber tip, with a length of 36 mu m, was fabricated by self-guiding photopolymerization. The two-wave interferometric operation was achieved by combining the light waves generated at the interface between the single-mode fiber and the polymer tip, and at the fiber tip end (Fresnel reflection). The Fabry-Perot interferometer is coherence addressed and heterodyne interrogated, resulting into a liquid refractive index resolution of approximate to 7.5 x 10(-4). (C) 2009 Optical Society of America

Abstract
A long-period grating written in the SMF-28 fibre was heat treated at 1000 degrees C for 15 days. The spectrum of the grating shifted to longer wavelengths and the resonances depth decreased as a result of structural relaxation. The background loss increased considerably for times longer than 200 h, and this loss is caused by devitrification of the fibre.