General purpose fiber optic hydrophone made of castable epoxy

Steven L. Garrett; David A. Brown; Brian L. Beaton; Kevin Wetterskog; John Serocki

doi:10.1117/12.24725

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1 February 1991 General purpose fiber optic hydrophone made of castable epoxy

Steven L. Garrett; David A. Brown; Brian L. Beaton; Kevin Wetterskog; John Serocki

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Proceedings Volume 1367, Fiber Optic and Laser Sensors VIII; (1991) https://doi.org/10.1117/12.24725
Event: SPIE Microelectronic Interconnect and Integrated Processing Symposium, 1990, San Jose, United States

Abstract

A fiber-optic, interferometric, flexural disk hydrophone cast from an epoxy resin is described. This hydrophone is designed in the shape of an enclosed, hollow cylinder with pairs of flat, spiral wound coils of optical fiber embedded in each sensing plate. An all-fiber Michelson interferometer is used to detect the optical phase shift which results from pressure induced strains in the optical fiber. The sensing coils are positioned in the plates in a manner to enhance the acoustic response and provide cancelation of acceleration induced signals. An epoxy resin was chosen for its relatively high tensile strength, its low Young's modulus, and its ability to cure at room temperature. The acoustic sensitivity of this sensor in both air and water was measured to be 0.277 0.005 rad/Pa (-131.2 dB re rad/μPa) which corresponds to a normalized sensitivity (formula available in paper)re 1 μPa^-1 below 1 .0 kHz. This measured result is in excellent agreement with simple elastic theory and the measured epoxy elastic constants. The normalized acceleration sensitivity is (formula available in paper)dB re g^-1. The acceleration-to-acoustic sensitivity ratio (figure-of-merit) of -134 dB re g4tPa is the largest reported to date for any fiber-optic hydrophone.

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Steven L. Garrett, David A. Brown, Brian L. Beaton, Kevin Wetterskog, and John Serocki "General purpose fiber optic hydrophone made of castable epoxy", Proc. SPIE 1367, Fiber Optic and Laser Sensors VIII, (1 February 1991); https://doi.org/10.1117/12.24725

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