This Recommendation describes two categories of single-mode optical fibre cable which are suitable for use in access networks, including inside buildings at the end of these networks. Both categories A and B contain two subcategories which differ in macrobending loss.

Category A fibres are optimized for reduced macrobending loss and tighter dimensional specifications compared to ITU-T G.652.D fibres and can be deployed throughout the access network. These fibres are suitable to be used in the O, E, S, C and L-band (i.e., throughout the 1260 to 1625 nm range). Fibres and requirements in this category are a subset of ITU-T G.652.D and therefore compliant1 with ITU-T G.652.D fibres and have the same transmission and interconnection properties.

Subcategory ITU-T G.657.A1 fibres are appropriate for a minimum design radius of 10 mm.

Subcategory ITU-T G.657.A2 fibres are appropriate for a minimum design radius of 7.5 mm.

Category B fibres are optimized for further reduced macrobending loss and therefore are capable of being used at very low values of bend radius. These fibres are for short reach distances (less than 1000 m) at the end of access networks, in particular inside buildings or near buildings (e.g., outside building riser cabling). The application length of ITU-T G.657.B fibre depends on the deployment strategy of each network operator. These fibres are suitable for use in the O, E, S, C and L-band (i.e., throughout the 1260 to 1625 nm range). Category B fibres are not necessarily compliant with ITU-T G.652.D in terms of chromatic dispersion coefficient and PMD specifications. These fibres however, are system compatible2 with ITU-T G.657.A (and ITU-T G.652.D) fibres in access networks.

Subcategory ITU-T G.657.B2 fibres are appropriate for a minimum design radius of 7.5 mm.

Subcategory ITU-T G.657.B3 fibres are appropriate for a minimum design radius of 5 mm.

The meaning of the terms used in this Recommendation and the guidelines to be followed in the measurement to verify the various characteristics are given in [ITU-T G.650.1] and [ITU-T G.650.2]. The characteristics of these fibre categories, including the definitions of the relevant parameters, their test methods and relevant values, will be refined as studies and experience progress.