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 system employing optical fibres for electronic speckle pattern interferometry is demonstrated. Single mode optical fibres are used to provide a reference beam and illumination of the object. The Michelson interferometer formed by the reference fibre and the fibre illuminating the target is used to compensate for environmentally induced phase noise. This compensation is achieved by using an electronic servo and a piezoelectric phase modulator to lock the Michelson at its quadrature point.

Abstract
A scheme to frequency multiplex a group of sensors based on all-fiber Michelson interferometers is presented. Lead insensitivity is obtained by using the two fiber leads of the configuration as an extra Michelson interferometer whose differential phase is kept constant by active compensation. Topics concerning the system design, sensor sensitivity, and crosstalk between sensors are investigated. Experimental and numerical computational results are presented.

Abstract

Abstract
A theoretical and experimental investigation, which allows the quantification of the general error function relative to the synthetic-heterodyne signal processing in interferometric fibre-optic sensors, is performed. The implications on the performance of interferometric sensing arrays are addressed. Considering the decrease of the readout phase errors, potentially more favourable implementations of this processing technique are proposed and compared.