This part of IEC 60793 is applicable to optical fibre categories B-652, B-653, B-654, B-655, B-656 and B-657. A map illustrating the connection of IEC designations to ITU-T designations is shown in Table 1. These fibres are used or can be incorporated in information transmission equipment and optical fibre cables. 
Three types of requirements apply to these fibres: 
• general requirements, as defined in IEC 60793-2;  
• specific requirements common to the class B single-mode fibres covered in this document and which are given in Clause 5;  
• particular requirements applicable to individual fibre categories or specific applications, which are defined in Annexes A to F. 
For some fibre categories (shown in the relevant family specifications), there are sub-categories that are distinguished on the basis of difference in transmission attribute specifications. The designations for these sub-categories are documented in the individual family specifications. 
Table 1 shows a map from the IEC designations to the ITU-T recommendations. The table also provides the normative annex in this document that contains the detailed specification as well as the name used to describe this fibre type in IEC 60793-2-50:2015. The ITU-T recommendations as well as the IEC categories/sub-categories within each recommendation 
are given. In some cases, as for Recommendation G.652, a given IEC designation maps to multiple categories in the ITU-T because the ITU-T categories are distinguished by cabled fibre attribute (PMD ) performance which are not distinguished in the IEC fibre specifications. 
 93-2- 50:2015 designation................................................................................................................ 8 Table 2 – Dimensional attributes and measurement methods ................................................ 11 Table 3 – Dimensional requirements common to all category B fibres ................................... 11 Table 4 – Mechanical attributes and test methods ................................................................. 11 Table 5 – Mechanical requi