High marks VDSL runs through its initial trials over carrier's local loops >BY SANDRA GUY, News Editor

Results from the first field tests of very high bit rate digital subscriber line show that the technology passed with flying colors. Although much has yet to be learned, Bell Canada's trials of Orckit Communications' VDSL modem prototypes show that the high-frequency technology works over local loops without interfering with other services.

"VDSL may soon become a practical option," said Nigel Cole, vice president of business development at Orckit.

Bell Canada's tests on half a dozen local loops indicate that VDSL "can work over real loops, provided that [the loops'] conditions respect the tolerance level of the VDSL system for a given bit rate," said Pierre Ferland, the carrier's associate director of network technology planning, in a statement issued last week.

Germany's Deutsche Telekom, Sweden's Telia and BT also have reported positive results from lab tests they've conducted on Orckit's CopperTrunk ORspeed I VDSL modem prototypes.

"We are studying VDSL as one of the keys to providing broadband access in Germany since most of our customers are within the reach capabilities of VDSL," said Bruno Orth, manager of components development for Deutsche Telekom's Access Networks.

The findings should help allay the concerns of standards and technical bodies that VDSL might cause radio frequency interference with services such as ISDN, high-bit-rate digital subscriber line or T-1, which would be deployed alongside it.

Many carriers appear likely to mix VDSL with asymmetrical digital subscriber line technology, giving them an extra service-provisioning option, Cole said.

As its name implies, the technology offers much higher bandwidth-downstream data rates as high as 52 Mb/s over copper twisted pair-than ADSL, which tops out at 6 Mb/s. That means it is likely to be a big hit with the private enterprise market by playing a key role in the provisioning of transparent local area network, frame relay and asynchronous transfer mode services, said Kieran Taylor, broadband consultant for TeleChoice, Verona, N.J.

Orckit's ORspeed modem can transmit at 13, 26 or 52 Mb/s downstream and 2 Mb/s upstream over distances of 4500, 3000 and 1000 feet, respectively.

The technology also is considered the most viable to deliver multimedia services such as high-speed Internet access, videoconferencing, video-on-demand and broadcast digital TV.

But VDSL also poses challenges. It requires a fiber-to-the-curb infrastructure and the ability to manage remote stations, Cole said. That means the technology must be extremely low-power and very densely integrated.

Orckit is working with Harris Corp.-a leader in low-noise data conversion technology-to develop a highly integrated chipset designed to meet those standards.