HR: 16:20h
AN: U32C-02 INVITED     [PDF]
TI: An Optical Fiber Sensor for Low-frequency Acoustics
AU: * Zumberge, M
EM: zumberge@ucsd.edu
AF: IGPP, Scripps Instn. of Oceanography Univ. of California, San Diego, La Jolla, CA 92093-0225 United States
AU: Berger, J
EM: jberger@ucsd.edu
AF: IGPP, Scripps Instn. of Oceanography Univ. of California, San Diego, La Jolla, CA 92093-0225 United States
AU: Blum, J
EM: johnblum@ucsd.edu
AF: IGPP, Scripps Instn. of Oceanography Univ. of California, San Diego, La Jolla, CA 92093-0225 United States
AB: We have developed a new distributed sensor for detecting pressure variations in the atmosphere. The instrument reduces noise due to air turbulence by averaging pressure along a line by means of monitoring strain in a long, sealed, tubular diaphragm with an optical fiber interferometer. A pair of optical fibers is wrapped in a spiral along the length of the tube. As the air pressure outside the tube changes, the associated strain in the tube (and fibers) is sensed by means of a Mach-Zender interferometer. Above 1 Hz, the optical fiber infrasound sensor (OFIS) is less noisy than microbarometers relying on mechanical filters. The records we have collected from an 89 m long OFIS indicate a new low noise limit in the band from 1 Hz to 10 Hz. At frequencies above the range of microbarometers, the OFIS is quieter than the best low-frequency microphones. Because the OFIS integrates pressure variations at light-speed rather than sound-speed, phase delays inside the sensor are negligible.
DE: 0350 Pressure, density, and temperature
DE: 0394 Instruments and techniques
SC: U
MN: 2003 Fall Meeting