IEC 60793-2-50:2012 is applicable to optical fibre categories B1.1, B1.2, B1.3, B2, B4, B5 and B6. A map illustrating the connection of IEC designations to ITU-T designations is shown in Annex I. These fibres are used or can be incorporated in information transmission equipment and optical fibre cables. This fourth edition cancels and replaces the third edition, published in 2008, and constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: - aligns the requirements with the relevant ITU-T Recommendations; - adds another option to the list of alternative primary coating diameter constructions in Table 2 and subsequent family specifications; - related modification of coating strip force in Tables 4 and 11; - removes the jumper cut-off wavelength in Table 5; - modifies B6 sub-categories; aligns B6-b MFD on B1.3 MFD. Keywords: information transmission equipment and optical fibre cables