The purpose of this document is to define a test that determines the suitability of optical fibre (Types A1a to A1d and B1 and B4) to withstand the environmental condition of change in temperature which may occur in actual use, store and/or transport. The test is primarily intended to permit the observation of effects of change in temperature over a given period. This procedure is conducted in accordance with IEC 60068-2-14, Test Nb.