12 June 2000 Characterization and application of FMCW coherence-addressed quasi-distributed absorption sensors
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We report on the performance parameters and a specific system application for a quasi-distributed absorption based sensor system. Coherence addressing of a series of open-path micro- optic sensing cells using FMCW is achieved by the interferometric mixing of signal pairs originating from glass/air interfaces in each cell. The interference patterns of all sensor cells add up (incoherently) at the detector, and by arranging the cells to be of differing lengths, each individual cell may be identified by its unique power spectrum in the frequency domain. We show theoretically and experimentally how to avoid 'cross terms' arising from the undesired interference between signals from optical paths associated with more that one cell. Results on system parameters including dynamic range, output stability, resolution, temperature and fiber bend influences are presented. For the specific application to distributed gas detection, where absorption linewidths of approximately 5 GHz are involved, we present a comparison of system performance for broad- and narrow-band absorbers.
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Miha Zavrsnik, Miha Zavrsnik, George Stewart, George Stewart, "Characterization and application of FMCW coherence-addressed quasi-distributed absorption sensors", Proc. SPIE 3986, Smart Structures and Materials 2000: Sensory Phenomena and Measurement Instrumentation for Smart Structures and Materials, (12 June 2000); doi: 10.1117/12.388125; https://doi.org/10.1117/12.388125

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