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Proceedings Paper

Digital spatial wavelength domain multiplexing (DSWDM) using a prism-grating-prism (PGP) and a CMOS imager: implementation and initial testing
Author(s): Martin B. Christiansen; Steve Chen; Christopher S. Baldwin; John B. Niemczuk; Jason S. Kiddy; Peter C. Chen; Harri K. Kopola; Mauri Aikio; Pekka Suopajarvi; Steven G. Buckley
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Paper Abstract

A CMOS imager-based spectrometer is used to interrogate a network containing a large number of Bragg grating sensors on multiple fibers as part of a proprietary structural health monitoring system. The spectrometer uses a Prism-Grating-Prism (PGP) to spectrally separate serially multiplexed Bragg reflections on a single fiber. As a result, each Bragg grating produces a discrete spot on the CMOS imager that shifts horizontally as the Bragg grating experiences changes in strain or temperature. The reflected wavelength of the Bragg grating can be determined by finding the center of the spot produced. The use of a random addressing CMOS imager enables a flexible sampling rate. Some fibers can be interrogated at a high sampling rate while others can be interrogated at a lower sampling rate. However, the use of a CMOS camera brings several specific problems in terms of signal processing. These include a logarithmic pixel response, a low signal-to-noise ratio, the long pixel time constant, obtaining sufficient process priority for the control program, and proper selection of the window of interest. In this paper we investigate computer algorithms and hardware solutions to address these problems. We also present experimental data to validate these solutions including calibration data and initial field-testing data with 24 sensors on 4 fibers.

Paper Details

Date Published: 6 August 2001
PDF: 8 pages
Proc. SPIE 4328, Smart Structures and Materials 2001: Sensory Phenomena and Measurement Instrumentation for Smart Structures and Materials, (6 August 2001); doi: 10.1117/12.435513
Show Author Affiliations
Martin B. Christiansen, Univ. of Maryland/College Park (United States)
Steve Chen, Univ. of Maryland/College Park (United States)
Christopher S. Baldwin, Systems Planning and Analysis, Inc. (United States)
John B. Niemczuk, Systems Planning and Analysis, Inc. (United States)
Jason S. Kiddy, Systems Planning and Analysis, Inc. (United States)
Peter C. Chen, Systems Planning and Analysis, Inc. (United States)
Harri K. Kopola, VTT Electronics (Finland)
Mauri Aikio, VTT Electronics (Finland)
Pekka Suopajarvi, VTT Electronics (Finland)
Steven G. Buckley, Univ. of Maryland/College Park (United States)


Published in SPIE Proceedings Vol. 4328:
Smart Structures and Materials 2001: Sensory Phenomena and Measurement Instrumentation for Smart Structures and Materials
Eric Udd; Daniele Inaudi, Editor(s)

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