This part of IEC 60793 provides a practical method for evaluating fibre performance in a defined environment. The purpose of this standard is to define a test that determines the suitability of optical fibres (types A1a to A1d and B1 to B4) to withstand the environmental condition of changes in temperature which may occur in actual use@ storage and/or transport. The test is primarily intended to permit the observation of effects of change of temperature over a given period. This procedure is conducted in accordance with IEC 60068-2-14@ test Nb. NOTE The applicability of this test to other fibre types is under study.