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
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.