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Proceedings Paper

Optical microphone with fiber Bragg grating and signal processing techniques
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Paper Abstract

In this paper, we discuss the realization of an optical microphone array using fiber Bragg gratings as sensing elements. The wavelength shift induced by acoustic waves perturbing the sensing Bragg grating is transduced into an intensity modulation. The interrogation unit is based on a fixed-wavelength laser source and - as receiver - a photodetector with proper amplification; the system has been implemented using devices for standard optical communications, achieving a low-cost interrogator. One of the advantages of the proposed approach is that no voltage-to-strain calibration is required for tracking dynamic shifts. The optical sensor is complemented by signal processing tools, including a data-dependent frequency estimator and adaptive filters, in order to improve the frequency-domain analysis and mitigate the effects of disturbances. Feasibility and performances of the optical system have been tested measuring the output of a loudspeaker. With this configuration, the sensor is capable of correctly detecting sounds up to 3 kHz, with a frequency response that exhibits a top sensitivity within the range 200-500 Hz; single-frequency input sounds inducing an axial strain higher than ~10nε are correctly detected. The repeatability range is ~0.1%. The sensor has also been applied for the detection of pulsed stimuli generated from a metronome.

Paper Details

Date Published: 17 June 2008
PDF: 11 pages
Proc. SPIE 7098, Eighth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, 70981E (17 June 2008); doi: 10.1117/12.803184
Show Author Affiliations
Daniele Tosi, Politecnico di Torino (Italy)
Massimo Olivero, Politecnico di Torino (Italy)
Guido Perrone, Politecnico di Torino (Italy)

Published in SPIE Proceedings Vol. 7098:
Eighth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications
Enrico Primo Tomasini, Editor(s)

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