ROADM Map

At this year's Supercomm, like the year before it, a raft of equipment vendors introduced new reconfigurable optical add/drop multiplexers. Or ROADM modules. Or enhancements to existing ROADMs. Or gear with ROADM capabilities.

For example, ECI Telecom added a wavelength-selective ROADM module to its multiservice provisioning platform. Meriton Networks added a 320 Gb/s card to its ROADM. Movaz Networks and NEC America introduced new ROADMs. Nortel Networks announced plans to include a ROADM module in its Common Photonic Layer platform. As perhaps the most popular and talked about technology in big optical networks, ROADMs have become a must for equipment vendors. But once on the bandwagon, they must navigate some fundamental choices in the way ROADMs are used and confront the high cost issues that plague the sector.

Though long-haul and metro optical networks stagnated for years following the hefty investments made during the telecom bubble days, they've begun to percolate again, as widespread broadband deployments (both wireless and wireline) load up networks with new traffic, forcing upgrades upstream in the metros and cores. And perhaps the most chosen technology for improving metro and core infrastructure is the ROADM.

ROADMs got their start in long-haul wavelength-division multiplexing networks, offering remote reconfigurability of wavelengths so that network operators didn't have to manually adjust the physical hardware of their networks onsite every time they wanted a change. ROADMs also granted network operators more flexibility, freeing them from the previously standard practice of having to plan networks very carefully and meticulously beforehand and committing faithfully to that plan.

ROADMs next appeared in regional and metro networks, using “wavelength blockers” to add or remove wavelengths from a ring — typically inexpensive liquid crystal devices that simply blocked signals selected for removal.

This year a more scalable method gained popularity: Wavelength-selective switches (WSSs) allowed more choices than just adding or dropping a given wavelength from a ring (see Telephony, April 25, page 28). Often using small angled mirrors, WSSs could switch a signal optically to one of perhaps three other rings. Some equipment vendors announced WSS ROADMs this year, including Fujitsu Network Communications, which dominated the North American metro ROADM market last year, and ECI. Other vendors, however, have described WSS as either too immature (as Tropic Networks told Telephony last spring), too expensive or both.

In fact, high costs have been a particular problem for ROADM technology in general. And participants in the ROADM space are trying all sorts of ways to shrink the economics of their already admired technology. At Supercomm this summer, Movaz Networks introduced a low-cost pizza-box-size ROADM to appease cost concerns. In late September, JDS Uniphase boasted having shipped its 1200th ROADM module, knowing that observers expect volume shipments to lower costs. At the European Conference on Optical Communications last month, WSS module manufacturer Metconnex demonstrated a cascade of 16 WSS ROADM modules at 40 Gb/s, claiming lower cost of ownership for carriers.

“There's more than one way to skin the cat,” said Infonetics principal analyst Michael Howard, referring to attempts to drive ROADM costs down.