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Fiber Optic MicrophoneResearch into advanced pressure sensors using fiber-optic technology is aimed at developing compact size microphones. Fiber optic sensors are inherently immune to electromagnetic noise, and are very sensitive, light weight, and highly flexible. In FY 98, NASA researchers successfully designed and assembled a prototype fiber-optic microphone. The sensing technique employed was fiber optic Fabry-Perot interferometry. The sensing head is composed of an optical fiber terminated in a miniature ferrule with a thin, silicon-microfabricated diaphragm mounted on it. The optical fiber is a single mode fiber with a core diameter of 8 micron, with the cleaved end positioned 50 micron from the diaphragm surface. The diaphragm is made up of a 0.2 micron thick silicon nitride membrane whose inner surface is metallized with layers of 30 nm titanium, 30 nm platinum, and 0.2 micron gold for efficient reflection. The active sensing area is approximately 1.5 mm in diameter. The measured differential pressure tolerance of this diaphragm is more than 1 bar, yielding a dynamic range of more than 100 dB.
Document ID
20020080692
Acquisition Source
Ames Research Center
Document Type
Other
Authors
Cho, Y. C.
(NASA Ames Research Center Moffett Field, CA United States)
George, Thomas
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Norvig, Peter
Date Acquired
August 20, 2013
Publication Date
March 9, 1999
Subject Category
Optics
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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