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18 May 2011 Resonant hydrophones based on coated fiber Bragg gratings. Part I: numerical analysis
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Proceedings Volume 7753, 21st International Conference on Optical Fiber Sensors; 775384 (2011)
Event: 21st International Conference on Optical Fibre Sensors (OFS21), 2011, Ottawa, Canada
In this work, we report the first evidence of the resonant behavior of underwater acoustic sensors constituted by a Fiber Bragg Grating (FBG) coated by a ring shaped overlay. The complex opto-acousto-mechanical interaction among an incident acoustic wave travelling in water, the optical fiber surrounded by the ring shaped coating and the FBG inscribed in an optical fiber is numerically analyzed by means of a commercial multiphysics software (COMSOLtm) implementing the finite element method. The numerical analysis has been performed in the frequency range 0.5-30 kHz, typically used in sonar applications. The retrieved numerical results, describing the opto-acoustic response of the optical hydrophone, highlighted that the coating is able to notably improve the sensitivity of the hydrophone, in the whole investigated frequency range, when compared to a FBG without coating. Furthermore, the hydrophone sensitivity versus the frequency presents characteristic resonances, which strongly improve the hydrophone opto-acoustic sensitivity with respect to the sensitivity background far from the resonances. As ascertained by means of a three-dimensional modal analysis of the hydrophone, the composite cylindrical structure of the sensor acts as an acoustic resonator accorded to the frequencies of the longitudinal vibration modes of the composite structure. In order to provide a full description of the sensor performances, we carried out also a parametric analysis by varying the geometrical and mechanical properties of the coating. The numerical results, besides outlining the resonant behavior of the coated FBG, also provided a tool for the design and optimization of the sensor performances which in turn can be tailored for specific Sonar applications.
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Massimo Moccia, Marco Pisco, Antonello Cutolo, Vincenzo Galdi, and Andrea Cusano "Resonant hydrophones based on coated fiber Bragg gratings. Part I: numerical analysis", Proc. SPIE 7753, 21st International Conference on Optical Fiber Sensors, 775384 (18 May 2011);

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