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20 April 1995 In-line fiber demodulator for interrogation of Bragg grating sensors
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Optical fiber Bragg gratings, first demonstrated by Hill in 1978, will see increasing deployment as sensors in smart structure applications due to their minimal insertion loss and small profile. Bragg grating sensors provide narrowband reflections from a periodic index discontinuity. Strain and temperature changes occurring on the grating induce a shift in the reflected wavelength. Currently, the most basic Bragg grating demodulation system consists of monitoring the reflected wavelength with an optical spectrum analyzer, but use of these devices is limited due to high costs and poor frequency response. In this paper, we propose using dual-mode optical fiber as an intensity based interrogation system. The modal birefringence of the fiber is wavelength dependent and therefore, the phase relationship between two modes changes as a function of the Bragg grating reflected signal. We describe the optical architecture for this demodulation system and provide experimental data for temperature and vibration response. It is predicted that with an optical source operating at 300 microwatts, less than 1 microstrain resolution is achievable.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Mark E. Jones, Jonathan A. Greene, Vikram Bhatia, Kent A. Murphy, Richard O. Claus, Anne E. Miller, and Ashish M. Vengsarkar "In-line fiber demodulator for interrogation of Bragg grating sensors", Proc. SPIE 2444, Smart Structures and Materials 1995: Smart Sensing, Processing, and Instrumentation, (20 April 1995);

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