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Proceedings Paper

Factors influencing the temperature sensitivity of PMMA based optical fiber Bragg gratings
Author(s): Wei Zhang; David J. Webb
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Paper Abstract

The Bragg wavelength of a PMMA based fiber grating is determined by the effective core index and the grating pitch, which, in temperature sensing, depend on the thermo-optic and thermal expansion coefficients of PMMA. These two coefficients are a function of surrounding temperature and humidity. Amorphous polymers including PMMA exhibit a certain degree of anisotropic thermal expansion. The anisotropic nature of expansion mainly depends on the polymer processing history. The expansion coefficient is believed to be lower in the direction of the molecular orientation than in the direction perpendicular to the draw direction. Such anisotropic behavior of polymers can be expected in drawn PMMA based optical fiber, and will lead to a reduced thermal expansion coefficient and larger temperature sensitivity than would be the case were the fiber to be isotropic. Extensive work has been carried out to identify these factors. The temperature responses of gratings have been measured at different relative humidity. Gratings fabricated on annealed and non-annealed PMMA optical fibers are used to compare the sensitivity performance as annealing is considered to be able to mitigate the anisotropic effect in PMMA optical fiber. Furthermore an experiment has been designed to eliminate the thermal expansion contribution to the grating wavelength change, leading to increased temperature sensitivity and improved response linearity.

Paper Details

Date Published: 2 May 2014
PDF: 7 pages
Proc. SPIE 9128, Micro-structured and Specialty Optical Fibres III, 91280M (2 May 2014); doi: 10.1117/12.2054210
Show Author Affiliations
Wei Zhang, Aston Univ. (United Kingdom)
David J. Webb, Aston Univ. (United Kingdom)

Published in SPIE Proceedings Vol. 9128:
Micro-structured and Specialty Optical Fibres III
Kyriacos Kalli; Alexis Mendez, Editor(s)

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