Papers by Author: Massimo Olivero

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Authors: Daniele Tosi, Massimo Olivero, Guido Perrone
Abstract: In the present work we report on the development of a low cost interrogation system of fiber Bragg grating sensors for structural health monitoring. The developed scheme uses two gratings and a directional coupler as sensing point, and it includes self-compensation of temperature effects. The reading equipment consists of a standard photodiode for telecom applications with custom signal-conditioning electronics. The characterization of multiplexed sensors, carried out in real framework conditions, shows that the system can work in a temperature range of -20÷+40°C, making strain measurements up to at least 320με with an accuracy of ~3% and an acquisition rate of 12 samples/min. Further, a budget evaluation is drawn to asses the feasibility of our interrogation system as a low cost solution to increase the extent of structural health monitoring in funds-limited applications.
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Authors: Massimo Olivero, Guido Perrone, Alberto Vallan, Silvio Abrate
Abstract: In the following we present a low-cost optical system for cracks evolution monitoring. The transducer principle is based on the variation of light transmitted between two facing fibers with their axial distance, exploiting the unique light-collecting capabilities of large-core polymer optical fibers. The characterization shows that the working range of the transducer is up to 3.5cm, with a resolution of 10$m and a repeatability of 5$m. With our current custom-developed control unit, up to four transducers can be arranged to provide a multi-axial displacement sensor or to simultaneously monitor four points for distributed sensing. A closed-loop light modulation/detection scheme is implemented to reduce the environmental noise sensitivity. The control unit is interfaced to a PC via USB port or via GSM/GPRS modem to automatically send periodical reports of the measurements and to issue warnings in case of displacements above a given threshold. Extensive tests in an environmental chamber have been carried out in order to extract calibration curves and to compensate for day-night and summer-winter temperature fluctuations.
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Authors: Daniele Tosi, Massimo Olivero, Alberto Vallan, Guido Perrone
Abstract: The paper analyzes the feasibility of cost-effective fiber sensors for the measurement of small vibrations, from low to medium-high frequencies, in which the complexity of the measurement is moved from expensive optics to cheap electronics without losing too much performance thanks to signal processing algorithms. Two optical approaches are considered: Bragg gratings in standard telecom fibers, which represent the most common type of commercial fiber sensors, and specifically developed sensors made with plastic optical fibers. In both cases, to keep the overall cost low, vibrations are converted into variations of the light intensity, although this makes the received signal more sensitive to noise. Then, adaptive filters and advanced spectral estimation techniques are used to mitigate noise and improve the sensitivity. Preliminary results have demonstrated that the combined effect of these techniques can yield to a signal-to-noise improvement of about 30 dB, bringing the proposed approaches to the level of the most performing sensors for the measurement of vibrations.
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