Irradiation studies of multimode optical fibres for use in ATLAS front-endlinks

The radiation tolerance of three multimode optical fibres has been investig ated to establish their suitability for the use in the front-end data links of the ATLAS experiment. Both gamma and neutron irradiation studies are re ported. A step-index fibre with a pure silica core showed an induced attenu ation of similar to 0.05 dB/m at 330 kGy(Si) and 1 x 10(15) n(1 MeV Si)/cm( 2) and is suitable for use with the inner detector links which operate at 4 0-80 Mb/s. A graded-index fibre with a predominantly germanium-doped core e xhibits an induced attenuation of similar to 0.1 dB/m at 800 Gy(Si) and 2 x 10(13) n(1 MeV Si)/cm(2) and is suitable for the calorimeter links which o perate at 1.6 Gb/s. Measurements of the dose rate dependence of the induced attenuation indicate that the attenuation in ATLAS will be lower. (C) 2000 Elsevier Science B.V. All rights reserved.