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Using Dual-wavelength Fiber Bragg Gratings for Temperature and Strain Sensing at Cryogenic TemperatureBy using dual-wavelength fiber-optic Bragg gratings, a new technique has been developed for sensing both temperature and strain simultaneously in cryogenic temperature range. Two Bragg gratings with different wavelengths were inscribed at the same location in an optical fiber to form a dual-wavelength sensor. By measuring the wavelength shifts that resulted from the fiber being subjected to different temperatures and strains, the wavelength-dependent thermo-optic coefficients and photoelastic coefficients of the fiber were determined. These coefficients were used to construct the elements of the K matrix, which enables to determine inversely the strain and temperature changes by measuring the wavelength shifts of the dual-wavelength Bragg grating. In this study, measurements were made over the temperature range from room temperature down to about 10 K, addressing much of the low temperature range of cryogenic tanks. A structure transition of the optical fiber during the temperature change was found from about 70 K to 140 K. This transition caused splitting of the waveforms characterizing the Bragg gratings, and the determination of wavelength shifts was consequently complicated. Several alternatives are proposed to resolve this problem. The effectiveness and sensitivities of these measurements in different temperature ranges are discussed. The separation of two wavelengths for the dual-wavelength Bragg grating has been widened to increase the sensitivities of measurement; however, this separation can still be covered in the scanning range from single scanning laser.
Document ID
20040008889
Acquisition Source
Langley Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Wu, Meng-Chou
(NASA Langley Research Center Hampton, VA, United States)
Prosser, William H.
(NASA Langley Research Center Hampton, VA, United States)
Rogowski, Robert S.
(NASA Langley Research Center Hampton, VA, United States)
DeHaven, Stanton L.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 7, 2013
Publication Date
January 1, 2003
Subject Category
Optics
Meeting Information
Meeting: JANNAF 39th Combustion/27th Airbreathing Propulsion/21st Propulsion Systems Harzards/3rd Modeling and Simulation Joint Subcommittee Meeting
Location: Colorado Springs, CO
Country: United States
Start Date: December 1, 2003
End Date: December 5, 2003
Sponsors: Department of the Navy, Department of the Army, NASA Headquarters, Department of the Air Force
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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