652 is the global baseline standard for single-mode optical fiber. It defines the geometrical, optical, and transmission characteristics of SMF, particularly optimized for operation at 1310 nm with low attenuation. 652 fibre was originally optimized for use in the 1310 nm wavelength region, but can also be used in. This document outlines the specifications for a single-mode optical fiber and cable designed for use around the 1310 nm zero-dispersion wavelength, suitable for both the 1310 nm and 1550 nm regions, and compatible with analogue and digital transmission. 657, IEC 60793, IEC 60794, TIA-568.