IEC 60793-1-54:2012 outlines a method for measuring the steady state response of optical fibres and optical cables exposed to gamma radiation. It can be employed to determine the level of radiation induced attenuation produced in Class B single-mode or Class A, category A1 and A2 multimode optical fibres, in either cabled or uncabled form, due to exposure to gamma radiation. This second edition cancels and replaces the first edition, published in 2003. It constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: launching conditions and optical sources have been reviewed and are better defined.Keywords: gamma radiation, optical fibres, optical cables