Alberto Vallan

Portable SPR refractometer for contamination analysis in a flowing liquid

The activity hereby presented is part of a project aimed at developing a compact all-fibre setup that exploits the Surface Plasmon Resonance (SPR) phenomenon to detect changes of chemical composition in a flowing liquid. The work has reached a lab prototype level, consisting of a plastic pipe with an embedded multi-mode optical fibre SPR sensor used as a refractometer. A demonstrator has been realised connecting the pipe to a water reservoir through a recirculating pump. Introduction of a contaminant into the flowing water produces a shift of the SPR. The system, tested with isopropyl/water mixtures, shows the capability to measure refractive index variations with a sensitivity of 2000 nm/RIU (RIU stands for Refractive Index Unit). The control unit is developed upon a commercial easy-to-use platform for demonstration and educational purposes.

Issues concerning intensity-based fiber sensors for non-contact vibration monitoring

The paper describes a simple fiber optic sensor for non-contact vibration measurements. The sensor is based on a couple of optical fibers placed in front of a vibrating target and derives the vibration amplitude from the changes of the reflected light intensity. A model of the optical sensor is introduced to predict the sensor behavior in different working conditions and for different sensor configurations. Then, issues concerning the sensor calibration in the presence of arbitrary targets, the choice of the sensor working distance, the strategies for sensitivity enhancement and the noise effects are investigated.