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Proceedings Paper

Pickup suppression in Sagnac-based fiber-optic acoustic sensor array
Author(s): Stéphane Blin; Michael Bishop; Krishnan Parameswaran; Michel J.F. Digonnet; Gordon S. Kino
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Paper Abstract

Large-scale acoustic fiber sensor arrays consisting of hundreds of hydrophones distributed along kilometers-long fiber buses are required for applications such as undersea oil exploration. Sagnac-based Sensor Arrays (SSAs) exhibit attractive performance; however the acoustic wave incident on the buses generates a pickup signal that can swamp the signals from the hydrophones. We propose, model, and demonstrate a simple technique for reducing this unwanted pickup by periodically inserting null sensors in the buses instead of hydrophones, so the pickup signal is measured at different locations along the buses. The signal from the null sensor (pickup only) is then subtracted from the signal seen by the adjacent hydrophone (true signal and pickup) to recover the true hydrophone signal. This paper describes in detail the signal processing steps used to perform this recovery. Applied to an experimental two-rung SSA, this technique produced a -18.6 dB pickup suppression for a pickup amplitude as large as 0.44 rad and signal amplitudes up to 0.44 rad, and -15 dB for a signal as large as 0.88 rad. These values are limited by the accuracy of the 8-bit data acquisition and/or electronic noise. With a low-noise 12-bit data acquisition, the pickup suppression for small signal amplitudes is predicted to be -35 dB. This work makes headway towards practical SSAs.

Paper Details

Date Published: 10 November 2005
PDF: 11 pages
Proc. SPIE 6004, Fiber Optic Sensor Technology and Applications IV, 600407 (10 November 2005); doi: 10.1117/12.633773
Show Author Affiliations
Stéphane Blin, Stanford Univ. (United States)
Michael Bishop, Stanford Univ. (United States)
Krishnan Parameswaran, Stanford Univ. (United States)
JDS Uniphase (United States)
Michel J.F. Digonnet, Stanford Univ. (United States)
Gordon S. Kino, Stanford Univ. (United States)

Published in SPIE Proceedings Vol. 6004:
Fiber Optic Sensor Technology and Applications IV
Michael A. Marcus; Brian Culshaw; John P. Dakin, Editor(s)

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