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Proceedings Paper

Fundamental limits in fiber Bragg grating peak wavelength measurements (Invited Paper)
Author(s): Shellee D. Dyer; Paul A. Williams; R. Joseph Espejo; Jonathan D. Kofler; Shelley M. Etzel
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Paper Abstract

We discuss the fundamental limits of fiber Bragg grating (FBG) wavelength metrology. High-accuracy wavelength measurements are critical for FBG strain sensors because a wavelength measurement uncertainty as small as 1 pm leads to an uncertainty of nearly 1 microstrain. We compare the measurement uncertainties for several common wavelength measurement systems, including tunable laser, optical spectrum analyzer (OSA), and interferometric. We show that when using an OSA it is difficult to achieve a measurement uncertainty better than 10 pm, and if the OSA is not accurately calibrated to a known wavelength reference, then the wavelength measurement uncertainty can be as large as 1 nm. We describe the uncertainties involved in determining peak and/or centroid wavelength from a measured data set. We also discuss calibration references for FBG sensor interrogation units. Wavelength references that are based on molecular absorption lines are often an excellent choice for FBG sensor calibration. However, some interrogation units require a wavelength reference unit based on narrow reflection lines rather than absorption lines. We investigated the application of athermally packaged FBGs as wavelength references, but we found that their wavelengths will drift with time and can undergo large jumps. We concluded that it is difficult to achieve stability better than 4 pm/year in athermally packaged FBGs.

Paper Details

Date Published: 23 May 2005
PDF: 6 pages
Proc. SPIE 5855, 17th International Conference on Optical Fibre Sensors, (23 May 2005); doi: 10.1117/12.623444
Show Author Affiliations
Shellee D. Dyer, National Institute of Standards and Technology (United States)
Paul A. Williams, National Institute of Standards and Technology (United States)
R. Joseph Espejo, National Institute of Standards and Technology (United States)
Jonathan D. Kofler, National Institute of Standards and Technology (United States)
Shelley M. Etzel, National Institute of Standards and Technology (United States)


Published in SPIE Proceedings Vol. 5855:
17th International Conference on Optical Fibre Sensors
Marc Voet; Reinhardt Willsch; Wolfgang Ecke; Julian Jones; Brian Culshaw, Editor(s)

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