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Proceedings Paper

New technique for fabrication of low loss high temperature stable high reflectivity FBG sensor arrays
Author(s): Stephen J. Mihailov; Dan Grobnic; Robert B. Walker; Cyril A. Hnatovsky; Huimin Ding; David Coulas; Ping Lu
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Paper Abstract

Fiber Bragg gratings (FBG) arrays in silica based optical fibers are increasingly used in applications involving system monitoring in extreme high temperature environments. Where operational temperatures are < 600 °C, traditional UVlaser inscribed FBGs are not appropriate since the induced Type I index change is erased. Instead two competing FBG technologies exist: 1) regenerative FBGs resulting from high temperature annealing of a UV-laser written grating in a hydrogen loaded fiber and 2) FBGs written with femtosecond infrared pulse duration radiation (fs-IR), either using the point-by-point method or using the phase mask approach. Regenerative gratings possess low reflectivity and are cumbersome to produce, requiring high temperature processing in an oxygen free environment. Multiple pulse Type II femtosecond IR laser induced gratings made with a phase mask, while having very good thermal stability, also tend to have high insertion loss (~ 1dB/grating) limiting the number of gratings that can be concatenated in a sensor array. Recently it has been shown that during multiple pulse type II thermally stable fs-IR FBG production, two competing process occur: an initial induced fs-IR type I FBG followed by a thermally stable high insertion loss type II FBG. In this paper, we show that if only a type I FBG is written using type II intensity conditions but limited numbers of pulses and then annealed above 600 °C, the process results in a type II grating that is stable up to 1000 °C with very low insertion loss ideal for an FBG sensor array.

Paper Details

Date Published: 12 May 2016
PDF: 6 pages
Proc. SPIE 9852, Fiber Optic Sensors and Applications XIII, 98520F (12 May 2016); doi: 10.1117/12.2220789
Show Author Affiliations
Stephen J. Mihailov, National Research Council Canada (Canada)
Dan Grobnic, National Research Council Canada (Canada)
Robert B. Walker, National Research Council Canada (Canada)
Cyril A. Hnatovsky, National Research Council Canada (Canada)
Huimin Ding, National Research Council Canada (Canada)
David Coulas, National Research Council Canada (Canada)
Ping Lu, National Research Council Canada (Canada)

Published in SPIE Proceedings Vol. 9852:
Fiber Optic Sensors and Applications XIII
Eric Udd; Gary Pickrell; Henry H. Du, Editor(s)

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