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 fibre (types A1a to A1d and B1 to B4) to withstand the environmental condition of immersion in distilled or demineralized water which may occur in actual use@ storage and/or transport. The test is primarily intended to permit the observation of effects of immersion in water over a given period. This procedure is conducted in accordance with IEC 60068-2-18@ test Rc. NOTE The applicability of this test to other fibre types is under study.