Distributed Bragg grating sensing technique for test article damage detection and monitoring

We report the use of a fiber-optic distributed sensing system to monitor structural fatigue on an aircraft undergoing a full scale fatigue test. This technique involves using optical frequency domain reflectometry to demodulate the reflected signals from multiplexed Bragg gratings that have been photoetched in the core of an optical fiber. The optical fibers, containing a high density of Bragg gratings, were applied along the surface of a Lockheed Martin P-3C Orion fatigue test article to assess the suitability of this technique for long-term structural damage detection and monitoring. Preliminary results indicate good agreement with quasi-collocated foil strain gauges and demonstrate great potential for supplementing or replacing conventional non-destructive evaluation techniques.