This part of IEC 60793 provides a practical method for evaluating fibre performance in a defined environment. The purpose of this standard is to determine the suitability of optical fibre (types A1a to A1d and B1 to B4) to withstand the environmental condition of high temperature (dry heat) which may occur in actual use, storage and/or transport. The test is primarily intended to permit the observation of effects of high temperature over a given period.