Fiber Optic Flexural Disk Microphone

David A Brown; T. Hofler; S. L. Garrett

doi:10.1117/12.948847

1 February 1989 Fiber Optic Flexural Disk Microphone

David A Brown, T. Hofler, S. L. Garrett

Proceedings Volume 0985, Fiber Optic and Laser Sensors VI; (1989) https://doi.org/10.1117/12.948847
Event: O-E/Fiber LASE '88, 1988, Boston, MA, United States

Abstract

A microphone consisting of a hollow cylinder whose flexible, circular endplates are bonded to pairs of flat spiral wound coils of optical fiber is described. When the endplate/disk is deformed due to a pressure difference, the outer and inner fiber coils experience opposite strains resulting in a "push-pull" optical path length difference which is detected in an all-fiber Michelson interferometer. The close proximity of the interferometric fiber coils, separated by the thin thermally conducting end plate, rejects thermal gradient induced signals. The addition of a second identical endplate and fiber coil pair at the opposite end of the cylinder doubles the acoustic sensitivity while canceling acceleration induced signals. The calculated and measured optical strain of a single plate, single coil sensor using static pressure, acoustic pressure, and acceleration are in good agreement and yield a sensitivity of 21 milliradians per Pascal per meter of optical fiber for an 8.0 cm diameter, 3.0 mm thick plate below its resonance frequency of 3 KHz.

Citation Download Citation

David A Brown, T. Hofler, and S. L. Garrett "Fiber Optic Flexural Disk Microphone", Proc. SPIE 0985, Fiber Optic and Laser Sensors VI, (1 February 1989); https://doi.org/10.1117/12.948847

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