Provides a method for measuring the steady state response of optical fibres and optical cables exposed to gamma radiation. It can be used to determine the level of radiation-induced attenuation produced in single-mode or multimode optical fibres, in either cabled or uncabled form, due to exposure to gamma radiation. This procedure focuses on two regimes of interest: the low dose rate regime suitable for estimating the effect of environmental background radiation, and the high dose rate regime suitable for estimating the effect of adverse nuclear environments.