1 May 1994 Digital demodulation scheme for wide-dynamic-range measurements with a fiber optic interferometer
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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, Lisa C. Giulianelli, A. Bruce Buckman, A. Bruce Buckman, Rodger M. Walser, Rodger M. Walser, Michael F. Becker, 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); doi: 10.1117/12.173961; https://doi.org/10.1117/12.173961
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