City Research Online

Abstract

This paper presents radiation resistant characteristics of fibre Bragg grating (FBG) sensors written in a photosensitive fiber and connected to a silica core radiation resistant optical fibre, aiming to develop a sensor system suitable for both sensing and data transmission in harsh environment. The silica core fluorine-down-doped clad optical fibre has been specifically designed and fabricated for this study using the modified chemical vapor deposition technique. Key waveguide parameters, including the width of the fluorine doped inner cladding have been optimized to obtain a low loss (<;0.2 dB/km) at the operating wavelength region of 1550 nm. The fibre fabrication process, mainly the deposition condition, has also been optimized to achieve smooth deposition and sintering of silica core layers, to minimize radiation induced absorption. As a result, radiation induced absorption of ~2.2 dB/km at 1550 nm under accumulated dose of 25 MRad at dose rate of 0.39 MRad/hr has been successfully achieved. To create an effective sensor system for harsh environmental conditions, this specialty fibre is connected to a number of FBGs (sensors) fabricated in photosensitive fibres prior to their extensive evaluations by being exposed to different accumulated dose of gamma radiation. Their corresponding Bragg wavelength shifts (BWS) and peak amplitudes were continuously monitored. It was found that the radiation induced BWS can be greatly reduced by shielding the sensors using stainless steel tubing. The temperature sensitivity and peak amplitude were found to be largely unchanged before and after exposure to Gamma radiation of 25 MRad which shows their potential use for temperature measurements in radiation environments with an uncertainty of around 0.1 °C.

Publication Type:	Article
Additional Information:	© 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
Publisher Keywords:	Fibre Bragg gratings, Gamma-ray effects, optical fibre, optical sensors, radiation effects, sensor system, silica core fibre
Subjects:	T Technology > TK Electrical engineering. Electronics Nuclear engineering
Departments:	School of Science & Technology > Engineering
SWORD Depositor:	Symplectic Administrator

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