6/3/2008 -- For years, ROADM -- that's shorthand for reconfigurable optical add-drop multiplexing -- was a long-haul network mainstay. Over the last few years, however, ROADM has started to trickle down into the metro core, thanks in part to an explosion in demand for packet-based services.

One upshot of this, according to market watcher Current Analysis, is that ROADM solutions have achieved surprising levels of maturity and market acceptance. They've progressed from two-degree wavelength blockers (developed for long-haul applications) to multi-degree solutions, which can support up to 10 directions of interconnection.

What's more, said Christina Howe Dietrich, senior analyst for optical infrastructure with Current Analysis, ROADM should continue to make, er, inroads into the metro space, such that ROADM devices should see widespread adoption over the next few years.

"One of the most notable changes is that WSS-based ROADMs have now become table stakes for vendors targeting the metro core ROADM market. Practically every vendor attempting to address this market has a generally available WSS-based, multi-degree ROADM," Dietrich said in a statement. "The reasons why are relatively common in the product development cycle. First, costs have come down. In addition, carriers are designing mesh metro networks with widespread interconnecting metro rings. Together these factors have driven carriers to indicate their preference for multi-degree ROADMs and the vendors have responded in turn."

Dietrich sees the ROADM push as a piece of another trend -- namely, feature and functionality density. Vendors are packing more features and functions than ever into their metro core offerings, including Layer 2 aggregation and switching capabilities, which Dietrich said have long been the provenance of centralized routers.

In addition, she continued, vendors are building management and control features into their metro core offerings. The upshot, according to Dietrich, is that the new crop of metro core devices actually consolidate the functionality of several different pieces of gear, "collapsing the metro network" and, in turn, reducing costs. --Stephen Swoyer