ITU releases coarse WDM standards

The International Telecommunications Union, which was in the forefront of defining channel spacing for dense wave-division multiplexing networks, has approved a new set of standards this week for coarse WDM.

ITU-T Recommendation G.695 was approved under the organization's fast-track approval process. It was given a accelerated schedule when members of ITU Study Group 15 recognized the fast pace at which CWDM was being adopted for Ethernet and storage-area networks.

Peter Wery, chairman of ITU-T Study Group 15, said the spec should be of interest to large and medium-sized carriers as well as to cable TV multisystem operators and enterprise network managers. Support for bit rates of both 2.5 and 1.25 Gbps were specified, with the latter added specifically for Gigabit Ethernet applications.

The spec also allows for unidirectional and bidirectional implementations, with target distances of 40 and 80 km.

The standard specifies the transmitter and multiplexer characteristics at the generating end of a CWDM link, along with the demux/receiver characteristics at the receiving end. It also defines the wavelength grid to be used for separating WDM channels, specifying 20-nm channel spacing that includes 18 wavelengths between 1271 nm and 1611 nm.

In the earlier G.694.2 specification for DWDM, channel "grids" were one of the key aspects of the standard. ITU created regular grids for 100, 50, 25, 12.5, and 6.25 GHz spacing.

- Loring Wirbel

EE Times