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Proceedings Paper

Study of the sapphire Bragg gratings probed with multimode and single mode signal from fiber collimators amd evanescent fiber tapers
Author(s): Dan Grobnic; Stephen J. Mihailov; Christopher W. Smelser; Huimin Ding
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Paper Abstract

Fiber Bragg gratings inscribed in sapphire fiber (SFBG) using IR femtosecond radiation and the phase mask method are potential sensors for very high temperature applications (⪆ 1200 °C) where silica based fiber sensors cannot operate due to the low silica glass transition temperature. Sapphire fiber is stable up to 2000 °C and the induced grating structures are stable above 1500 °C. The main difficulty of using the femtosecond IR laser induced sapphire fiber grating sensors is related to the probing of the sensor. Since the sapphire fiber is an air-clad rod, propagating probe light is highly multimode for the commercially available fiber diameters of between 60 and 200 μm. The interrogation of the Bragg grating sensor has to be made either in a multimode regime or an attempt to propagate a single mode signal in the multimode sapphire fiber is required. A study of the probing signal coupling to the SFBG and its influence on the spectral response of the sapphire grating is presented. High-order retro-reflective FBGs were fabricated in crystalline sapphire fibers with diameters in the 60 to 200 μm range. The sapphire Bragg gratings was probed with signals from a tuneable laser launched through a single-mode fiber into the input port of multimode fiber couplers made from 60 and 105 μm core diameter fiber. In the single mode regime, the excitation of the sapphire fiber was made with fiber collimators and fiber tapers.

Paper Details

Date Published: 30 October 2007
PDF: 8 pages
Proc. SPIE 6796, Photonics North 2007, 67961J (30 October 2007); doi: 10.1117/12.778896
Show Author Affiliations
Dan Grobnic, Communications Research Ctr. (Canada)
Stephen J. Mihailov, Communications Research Ctr. (Canada)
Christopher W. Smelser, Communications Research Ctr. (Canada)
Huimin Ding, Communications Research Ctr. (Canada)

Published in SPIE Proceedings Vol. 6796:
Photonics North 2007
John Armitage, Editor(s)

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