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1 May 1994 Digital demodulation scheme for wide-dynamic-range measurements with a fiber optic interferometer
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We model and experimentally demonstrate a Hilbert Transform-based signal processing scheme that maps optical phase shifts in a fiber optic interferometer into electrical phase shifts in the harmonics of an imposed modulation frequency. The interferometer is a two-loop Mach- Zehnder with only one loop exposed to the measurand. A phase modulation at a convenient carrier frequency is applied to the first loop, and its second harmonic is applied to the second loop. A 30 Hz measurand test signal is applied, upshifted, and demodulated using a simple digital signal processing algorithm. In contrast to the nonlinear dependence of transmittance on phase shift of conventional interferometric sensors, this digital signal processing scheme yields a demodulated output that is linear with phase shift, and is capable of extracting measurands with dynamic ranges much greater than 2 (pi) radians.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Lisa C. Giulianelli, A. Bruce Buckman, Rodger M. Walser, and Michael F. Becker "Digital demodulation scheme for wide-dynamic-range measurements with a fiber optic interferometer", Proc. SPIE 2191, Smart Structures and Materials 1994: Smart Sensing, Processing, and Instrumentation, (1 May 1994);

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