New technique for fabrication of low loss high temperature stable high reflectivity FBG sensor arrays

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DOIResolve DOI: http://doi.org/10.1117/12.2220789
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TypeArticle
Proceedings titleFiber Optic Sensors and Applications XIII
Series titleProceedings of SPIE; no. 9852
ConferenceFiber Optic Sensors and Applications XIII, 12 May 2016
ISSN9781510600935
Article number98520F-1
Subjectfiber optic sensor; fiber Bragg grating; femtosecond laser machining; photosensitivity
AbstractFiber 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.
Publication date
PublisherSPIE
LanguageEnglish
AffiliationNational Research Council Canada; Security and Disruptive Technologies
Peer reviewedYes
NPARC number23000246
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Record identifierb08a2003-4584-42a0-941f-8508e8960a8d
Record created2016-06-28
Record modified2017-09-13
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