Going the distance: MCI mulls Pirelli technology for optical extension

As part of its quest toward creating an all-optical network, MCI is testing a technology developed by Pirelli Cables and Systems to help alleviate lightwave dispersion and reduce carriers' reliance on electrical regeneration equipment.

The test is based on Pirelli's soliton technology. In optical networking parlance, solitons are pulses of light that retain their shape as they travel along fiber, helping network operators overcome lightwave dispersion and transport optical signals over longer distances.

In recent trials, MCI sent a single data traffic stream at speeds of 10 Gb/s more than 900 km over existing fiber without regeneration. Using dense wavelength division multiplexing, the carrier transmitted four 10 Gb/s data streams more than 450 km without using regenerators.

"Solitons allow us to go longer distances without requiring us to put regenerators in the spans," said Jack Wimmer, executive director of network technology and planning at MCI. "The regenerators are one of the things that stand in the way of the transparency option."

Having a completely transparent optical network means no electrical conversion or regeneration is required throughout the network, which can have significant cost advantages.

"When I come to a regeneration point, I need a separate regenerator for each wavelength," Wimmer said. "There's a big economic incentive in removing them from the network."

"The longer you can go in a network without regenerating, the more money it saves you," said Matt Steinberg, director of optical networking at Ryan, Hankin and Kent.

Pirelli's WDM systems feature soliton transmitters that generate pulses shaped and powered to eliminate lightwave dispersion over long-distance fiber transport.

"We are narrowing the pulse and increasing the power so much that the non-linear effects disappear," said Neal Stoker, director of marketing for Pirelli Telecom Systems.

Controlling dispersion becomes more important as desired transport speeds increase, Steinberg noted. "With the current generation of fiber, as you go further, dispersion becomes more critical," he said. "At OC-48 you might not have to manage dispersion, but at OC-192 you do."

Despite the successful trial results, Wimmer estimated that MCI is still 18 to 24 months away from large-scale deployment.