Applicable to optical fibre types B1.1, B1.2, B1.3, and categories B2 and B4. 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 standard and which are given in Clause 3; Particular requirements applicable to individual fibre types or specific applications, which are defined in the family specifications of Annexes A to E.