IEC 60793-2-50:2008 is applicable to optical fibre types B1.1, B1.2, B1.3, and categories 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. The main technical changes of this edition include: - aligns the requirements with the relevant ITU-T Recommendations, including tightening the tolerances of many parameters - adds a new category, B5, which corresponds to the fibres defined in ITU-T Recommendation G.656 and - adds a new category, B6, which corresponds to the fibres defined in ITU-T Recommendation G.657.