Abstract
This work presents an extensive, comparative study of the gamma and electron radiation effects on the behaviour of femtosecond laser-inscribed fibre Bragg gratings (FBGs) using the point-by-point and plane-by-plane inscription methods. The FBGs were inscribed in standard telecommunication single mode silica fibre (SMF28) and exposed to a total accumulated radiation dose of 15 kGy for both gamma and electron radiation. The gratings’ spectra were measured and analysed before and after the exposure to radiation, with complementary material characterisation using Fourier transform infrared (FTIR) spectroscopy. Changes in the response of the FBGs’ temperature coefficients were analysed on exposure to the different types of radiation, and we consider which of the two inscription methods result in gratings that are more robust in such harsh environments. Moreover, we used the FTIR spectroscopy to locate which chemical bonds are responsible for the changes on temperature coefficients and which are related with the optical characteristics of the FBGs.
Highlights
Fibre Bragg gratings (FBGs) are widely used in many applications as sensing elements [1,2]
We analysed the samples in terms of reflectivity, full width at half maximum (FWHM) bandwidth, coupling coefficient (k), refractive index modification (∆nmod ), and resonance wavelength with respect to the equation below, π∆nmod ηL
It seems that this area is not related with the temperature coefficient of the fibre Bragg gratings (FBGs), since similar changes were observed for either sample exposed to electron or to gamma radiation
Summary
Fibre Bragg gratings (FBGs) are widely used in many applications as sensing elements [1,2]. They are often preferred to electrical sensors due their small size and flexible design, offering immunity to electromagnetic interference and their unique multiplexing capabilities. Where ne f f is the effective refractive index and Λ is the modulation period. These optical components are intended to be used either as radiation or temperature sensors in harsh radiation-ionising environments. The temperature response of the FBGs is denoted as creativecommons.org/licenses/by/
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