Distributed Fiber Optic Laser Ultrasonic System
Patent, Filed 2 Dec 1998, Patented 8 Aug 2000
DEPARTMENT OF THE NAVY WASHINGTON DC
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An optical fiber coupled to a high power laser carries laser energy to laser-activated sound generating materials disposed at intervals along its length. The sound-generating materials are acoustically coupled to an object or objects to be monitored. Acoustic reflections from the objects modulate the periods of Bragg gratings formed in a separate core of the fiber, or in the core of a separate fiber. The modulation of a Bragg grating period is detected as a Doppler shift in an interrogation beam reflected by the grating.