From the ITU-T Newslog: A new standard from ITU-T's Study Group 15 gives network operators the ability to deploy multi-vendor dense wave division multiplexing (DWDM) systems in a metro environment. Defining specifications for interoperability in this field is seen as a ground-breaking achievement, where previously there has been domination by proprietary systems.
WDM technology is used by the owners of optical fibres to maximise their capacity. The technology achieves this by simultaneously operating an optical fibre pair at more than one wavelength. Since operators wish to maximize their cable plant investments and deploy increasingly bandwidth hungry services in a multi-vendor environment, standards development in this field is seen as crucial.
Until now DWDM systems, which have the capability of carrying a high number of channels (up to 80) on a single optical fibre pair, have been deployed in core fibre networks that cover great distances. A different WDM technology CWDM (the C stands for coarse) was the first standardised solution for metropolitan areas, but CWDM systems only have the capability of carrying a limited number of channels (up to 12 now, but in the future 16).
This standard (ITU-T Recommendation G.698.1) has been driven by operators and allows them to benefit from the greater capacity of DWDM systems in metropolitan environments while being able to deploy system elements from multiple vendors. The current version of this Recommendation covers distances in the range of 30 - 80 km.
These new specifications have been made possible by the use of a fundamentally different methodology to that used previously according to the experts who developed it. The so-called 'black-link'-approach is seen as a new direction in the standardization of WDM systems, providing a powerful tool to enable agreement on multi-vendor interoperability in a previously proprietary environment.