400G is an important standard for high-capacity Ethernet client interfaces. Originally known as IEEE 802.3bs, 400G was officially approved in December of 2017 and is part of a broader family of related tec.
The standard specifies the geometrical, mechanical, and transmission attributes of a single-mode optical fibre as well as its cable. The fibre has zero-dispersion wavelength around 1310 nm as per how it was designed, however it can also be used in the 1550 nm wavelength region.