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27 November 1996 Multiplexed fiber optic Bragg grating strain sensor system for use in marine vehicle testing
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A novel approach for the interrogation of multiplexed fiber optic Bragg-grating strain sensors is presented. It is a time domain multiplexing technique based on using pulsed radio frequency modulation combined with slow wavelength tuning of a distributed feedback laser diode. A derivative- type signal for each sensor is generated in the receiver and the instantaneous Bragg-wavelength, proportional to the applied strain, is determined from the timing of the zero- crossing of the derivative signal. The Bragg-gratings, all with the same Bragg wavelength, are coupled to the output of a 1 x N fiber optic coupler with appropriate relative fiber delays between each sensor to enable time-division multiplexing. A four channel system has been designed, implemented, and tested in a laboratory environment, and later mounted on the hull of a scaled catamaran model and tested at a ship testing facility. The strain measurements were compared to measurements using standard strain gauges. The system had a dynamic range of about 680 microstrain, limited by the laser diode current tuning, and a resolution of approximately 1 microstrain, limited by interferometric background signals. The bandwidth was limited to about 50 Hz due to the laser diode tuning response.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Dag Roar Hjelme, Bjorn Bakke, Jan S. Rambech, and Steinar Neegaard "Multiplexed fiber optic Bragg grating strain sensor system for use in marine vehicle testing", Proc. SPIE 2838, Distributed and Multiplexed Fiber Optic Sensors VI, (27 November 1996);

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