This Recommendation describes a dispersion-shifted, single-mode optical fibre and cable which has a nominal zero-dispersion wavelength close to1550 nm, and a dispersion coefficient which is monotonically increasing with wavelength. This fibre isoptimized for use in the 1550 nm region, but may also be used at around 1310 nm subject to the constraints outlined in this Recommendation. Some provisions are made to support transmission at higher wavelengths up to 1625 nm and lower wavelengths down to 1460 nm. Chromatic dispersion coefficient values at these wavelengths may be specified to support coarse wavelength division multiplexing (CWDM) systems that do not have significant impairment due to non-linear effects.