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Proceedings Paper

Advances in fiber gratings: technology, applications, and reliability
Author(s): Hans G. Limberger; Dimitris Varelas
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Paper Abstract

Basic components and devices for optical fiber sensor and telecommunication networks should exhibit survival times of 20 to 40 years. Fiber gratings are important basic devices for such networks. This demands good thermal and mechanical reliability of the grating itself. However, as it will be shown in this paper, both reliability aspects depend strongly on factors like grating fabrication conditions, the fiber used, a possible photosensitization process, etc. The thermal stability of fiber gratings is strongly linked to the fiber, its co-dopants and possible photosensitization by hydrogen loading. Determining the electron distribution of the involved defects can assess the reliability. To a first approximation the decay is determined by the decay frequency v0. Good thermal stability over 25 years at 40 °C can be predicted for germanosilicate fibers if the gratings are annealed for 110 hours at T≈120 °C. Higher operating temperatures demand higher annealing temperatures for reasonable annealing times and do need therefore special protections like polyimide coatings. The mechanical breaking strength of fiber gratings is related to the grating fabrication process and fiber preparation. For telecommunication applications, gratings are in general fabricated off-line. In this case, careful chemical fiber stripping and handling is needed. When gratings are written using pulsed KrF excimer laser irradiation a considerable mechanical degradation is observed, which depends on the irradiation conditions. In contrary, frequency doubled CW-Ar+ laser irradiation almost preserves the median breaking stress. Gratings fabricated by one single laser shot or written through the fiber coating show almost no degradation. However, due to their low reflectivity the use of single shot gratings is mostly restricted to sensor applications. The fabrication of grating devices by irradiation through the coating is still limited to index modulations of 10-4 due to coating degradation.

Paper Details

Date Published: 28 September 1999
PDF: 34 pages
Proc. SPIE 10295, Reliability of Optical Fibers and Optical Fiber Systems: A Critical Review, 1029508 (28 September 1999); doi: 10.1117/12.367127
Show Author Affiliations
Hans G. Limberger, Swiss Federal Institute of Technology/Lausanne (Switzerland)
Dimitris Varelas, Swiss Federal Institute of Technology/Lausanne (Switzerland)

Published in SPIE Proceedings Vol. 10295:
Reliability of Optical Fibers and Optical Fiber Systems: A Critical Review
Dilip K. Paul, Editor(s)

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