Fiber bragg grating strain sensor demodulation with quadrature sampling of a mach-zehnder interferometer.
A simple and highly sensitive phase-demodulation technique is proposed, and its use for a fiber Bragg grating strain sensor is experimentally demonstrated. Sampling a phase-modulated Mach-Zehnder output with controlled time delay produced two quadrature data streams that have relative quadrature phase difference (90 degrees ). The Bragg wavelength-dependent phase information is extracted by application of digital arctangent function and phase unwrapping to the quadrature signals. By use of this technique with a reference grating, strain sensing at as much as a 30-kHz sampling rate was obtained with strain resolution of 3.5 microstrains and 6 nanostrains/[square root]Hz in quasi-static and dynamic strain measurements, respectively.
Song
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Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
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Ruffin
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