NEW YORK -- Packet-Optical Transport Evolution -- Telecom operators need more flexible optical equipment to facilitate the migration to 100-Gbit/s networks and beyond, Glenn Wellbrock, director of backbone network architecture for Verizon Enterprise Solutions , said today.

Speaking at Light Reading's Packet-Optical Transport Evolution conference here today, Wellbrock said reconfigurable optical add/drop multiplexers, in particular, need to be "colorless, directionless, and contentionless" in order to enable rapid reconfiguration of network traffic without manual intervention.

Wellbrock also challenged telecom equipment vendors to sort out where the industry will go after 100 Gig is implemented, so that ROADMs being built today will be able to support that continued migration.

"I'm not saying what the next bit rate will be, it could be 400 Gig or more, but it definitely will be more than 100 Gig and will require more than the 50GHz channel spacing we use today," Wellbrock said. "We need to work out the modulation format, and part of that challenge is that the next generation is not necessarily centered on an ITU-T grid."

Today's ROADMs are limited in their flexibility, requiring manual intervention if channel (wavelength color) or signal direction is changed at the access or egress point of the network, Wellbrock noted, or if a signal needs to be routed around network congestion points. Since manual reconfigurations not only drive up operations costs but also introduce potential human errors or dirty connections, telecom network operations need more flexibility for automated reconfiguration.

The optimum circumstance would be the ability to do a "network defragmentation," just like a PC defragmentation, he said.

"Networks get built one or several links at a time. In New York, there are 200 nodes connected together. As soon as you turn up a node, you put traffic on it. Now when you install a new node with a more direct path, you'd like to be able to use that path. Today, that is a more manual operation, so it usually doesn't get done until you are in such a bind because of congestion that you have to do it."

But if ROADMs came with a big red "defrag" button that would enable the network to be periodically returned to its optimal state, Wellbrock observed, they could operate more efficiently and at a lower cost. Greater flexibility, he believes, would also enable better network maintenance and more efficient network restoration and bandwidth adjustments.

Wellbrock acknowledged that more flexible ROADMs would come with a higher price tag, adding that Verizon would like to start conversations with vendors as to what the cost might be.

He also cautioned the POTE audience not to expect Sonet equipment to disappear from the network anytime soon, as network operators continue to support TDM services, and lack some of the tools necessary to make the shift to Carrier Ethernet.

"We don't have the necessary tools to be able to provide proper Ethernet support -- things like fault management and alarms. Until we have full Ethernet capability across multiple vendors, we have to go over TDM."

— Carol Wilson, Chief Editor, Events, Light Reading