Digital demodulation scheme for wide-dynamic-range measurements with a fiber optic interferometer

Lisa C. Giulianelli; A. Bruce Buckman; Rodger M. Walser; Michael F. Becker

doi:10.1117/12.173961

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1 May 1994 Digital demodulation scheme for wide-dynamic-range measurements with a fiber optic interferometer

Lisa C. Giulianelli, A. Bruce Buckman, Rodger M. Walser, Michael F. Becker

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Proceedings Volume 2191, Smart Structures and Materials 1994: Smart Sensing, Processing, and Instrumentation; (1994) https://doi.org/10.1117/12.173961
Event: 1994 North American Conference on Smart Structures and Materials, 1994, Orlando, FL, United States

Abstract

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.

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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); https://doi.org/10.1117/12.173961

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