Bob Metcalfe

SAN DIEGO--Terabit Ethernet networks are coming, said Bob Metcalfe, a partner at Polaris Ventures who is credited with having invented Ethernet more than 35 years ago. But it’s not clear exactly when, he said. And it’s less clear what network architectures will be needed to enable them.

Addressing the OFC NFOEC show today, Metcalfe said terabit-per-second Ethernet networks might be deployed by 2015, adding, “I’m not sure.”

Network traffic is certainly escalating dramatically, he pointed out. This week futurist George Gilder predicted the Internet would carry a zetabyte of traffic annually by 2015. That’s a one followed by 21 zeroes.

To stay ahead of that increasing demand, carriers will eventually need to introduce dramatic and fundamental changes in the way optical networks are currently built, Metcalfe said.

“To get to terabit Ethernet, we’ll have to break out of a lot of constraints,” he said, including 1550-nanometer lasers and 15-GHz spacing between them. New modulation schemes will be needed for the coming network, he said, as well as “new fiber, new lasers, new everything.”

The need to replace existing technologies will create “chaos,” Metcalfe said, but also opportunity for equipment vendors. Future demand might be met by deploying fiber with vacuum cores, for example, or carbon fibers rather than silicon fibers. Carriers might deploy more all-optical gear or even more free-space optical gear, he said.

But a key technology in accommodating future traffic growth is one that emerged in the previous decade: dense wavelength division multiplexing. And it is far more complex than Ethernet. “Ethernet has to confront the fact that DWDM is inherently a harder problem, so the smart alecs in the Ethernet world have a comeuppance coming,” he said. “There are silver bullets, and DWDM is one of them.”

But even DWDM has room to improve to keep up with coming network demands, Metcalfe said. Addressing the crowd of optical engineers, he added, “Thanks for DWDM, but you’re not done. Please keep going.”