Abstract
We present optical sensors based on slotted multimode interference waveguides. 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 low-loss silicon oxynitride (SiON) which is highly stable to the reactivity with biological agents and processing chemicals. Sensors made with this technology are suited to high volume manufacturing. Copyright © 2009 M. Mayeh et al.

Abstract

Abstract

Abstract
A novel self-referencing parameter for electro-optical WDM networks in reflective configuration for remote fiber-optic intensity sensors is reported and experimentally tested. In this configuration electrical delay lines are deployed at the processing unit, instead of long delay fiber coils in each measuring point; providing a more compact sensor-head and an easy-reconfigurable operation point. The measurement parameter is defined as the ratio between voltage values at the reception stage for different electrical phase-shifts and it is analyzed following the Z-transform formalism. Measurements validating the theoretical model are reported and self-referencing and crosstalk properties of the network are analyzed. © 2009 SPIE.

Abstract
A fibre optic Fabry-Perot sensing structure based on suspended-core fibre is presented. The interferometric structure is formed when a small length of suspended-core fibre with three or four holes is spliced to the end of a standard single mode fibre. The sensing structure is implemented firstly for strain and temperature measurement, and secondly for refractive index measurement. The interrogation of the sensing structure is obtained for the first implementation by the wavelength variation, and for the second implementation through the fringe visibility and through the analysis of the fast Fourier transform. © 2009 SPIE.

Abstract
A fiber-optic sensor for torsion measurement, based on a two-LP-mode operation in ultra high birefringent photonic crystal fiber (PCF) is described. The structure of the photonic crystal fiber presents two large asymmetric holes adjacent to the core fiber. When linearly polarized light is injected in x or in y directions, respectively, two different interferometers can be obtained. In one of these cases, as torsion is applied to the ultra Hi-Bi PCF a beat between the two interferometers is formed due to the simultaneous excitation of the two polarization states. The detection technique to read the torsion sensor is based on the analysis of the Fast Fourier Transform (FFT), which is an alternative and simple solution. The sensor exhibited reduced sensitivity to temperature and also to strain. © 2009 SPIE.