Full-spectrum single-mode fibre in accordance with ITU-T G. D with optimised transmission characteristics. Suitable for the operating wavelengths in all FTTx networks. The IEC and ITU-T and under zero-dispersion wavelength and the resulting displacement of the cut-off wavelength single-mode fiber is divided into six types. 655, as required by telecom systems manufcturers and their customers. 652 (Tables A, B, C & D), IEC Specification 60793-2-50 Type B1. 3, TIA/EIA 492-CAAB and Telcordia Generic Requirements GR-20-CORE. A map illustrating the connection of IEC designations to ITU-T designations is shown in Annex I.