IXC Goes Long with OC-192 DWDM; Transponder Solutions on the Way

The future of IXC Communications Inc. (Austin, TX) is not all OC-192, even as it lays claim to the longest deployment of 8-channel OC-192 DWDM. Unlike some of its rivals, the carrier plans to continue deploying transponder-based DWDM equipment alongside its embedded OC-192 architecture to run Internet protocol (IP) over DWDM.

"We like the transponder technology, especially for the express architecture," says Mike Vent, IXC's executive vice president of network operations and engineering, referring to routes with few stops. Sweetening the deal are speedy optical interfaces on IP routers, which eliminate the need for a SONET add/drop multiplexers (ADM) and terminals altogether.

OC-192 router interfaces are on the way, but IXC isn't holding out. "OC-48 light pipes across the country are a low-cost transport solution," Vent says, "much cheaper than OC-192 ADMs and terminals."

Rather than take what he calls a bandwidth-solves-everything approach, Vent believes in carefully engineering the network. "I have a lot of fiber. It's just a matter of matching up IP customer requirements with cost optimization for distribution."

Alternative view
IXC's dual OC-48 and OC-192 platforms are somewhat unique among similar-generation rival carriers (OC-192 is a popular option for new fiber builds). "No one could compete on an OC-48 level with an OC-192 network—it can't happen and it won't happen," says Larry Seese, executive vice president of network engineering and operations at Qwest Communications (Englewood, CO).

Seese maintains that beyond a total capacity of 10 Gbps, OC-48 equipment becomes 35 to 50% more expensive than OC-192. Even with the OC-48 interfaces on IP routers, he's not buying it, because he says an IP-over-DWDM architecture predicates mesh routing, point-to-point links, and complex techniques to ensure reliability that drive up cost.

But Seese and Vent do agree on the virtues of OC-192, and IXC's OC-48 DWDM transport deployment will not preclude ramping up OC-192 facilities. With the OC-192 DWDM hardware in place, Vent reports that the software to handle 16-channel DWDM should be ready by early next year.

Configuring OC-192
For now, IXC is running up to eight channels of OC-192, including what it believes is the longest such route at 2,000 miles connecting New York City and Dallas. "A lot of carriers are talking about [deploying OC-192 DWDM], but they haven't been doing it over long network segments," Vent says, adding that the distance does not require any dispersion management beyond that inherent in the system riding over IXC's non-zero dispersion shifted fiber.

Click here to see Block Diagram.

IXC runs four channels of Nortel's (Brampton, ON) OC-192 and DWDM in each direction on the long route. Some 68% of the traffic is live—the rest of the capacity is allocated for backlog and an unnamed Internet service provider (ISP) with which IXC scored a major contract earlier this year, Vent says.

Using fixed add/drop points of presence, IXC typically configures two or three wavelengths as express routes (comprising a drop or two) and one local route with several drops. "There's a much bigger demand for coast-to-coast 'OC-' products than distribution," Vent notes, adding that the situation may change with the evolving needs of competitive local exchange carrier and ISP customers. "But now, the demand is for the five major cities. We don't have to break the traffic down below the optical levels."

But breaking down the traffic is what the embedded OC-192 configuration does well, Vent continues. "Most of our big contracts are for OC-3 and OC-12," which suits the granularity of OC-192. IXC has configured four fibers on its network for bidirectional lineswitched rings (BLSR) and 16-channel OC-192 DWDM. Another four fibers are slated for transponder-based DWDM systems, Vent says.

Different vendors, different platforms
Nortel equipment currently dominates IXC's network in a 70/30 split with second vendor Alcatel (Richardson, TX), Vent reports, after Nortel won the bid to help IXC in the carrier's rush to complete a coast-to-coast network segment. The win put Nortel OC-192 equipment in the western region of IXC's network, which was previously the domain of Alcatel.

Tipping the balance of the bidding war was a lot of pre-outfitting of provisioning technology on Nortel's part, Vent reports. He estimates that the price of a full suite of OC-192 SONET equipment, DWDM filters, and optical amplifiers has dropped nearly 50% in the last year. Meanwhile, IXC is still trialing Alcatel OC-192 equipment, reports Daryl Chaires, manager of new business development at Alcatel.

IXC is now negotiating price points for more transponder-based DWDM. IXC plans to activate 13,000 route miles of fiber in the first quarter of 1999. Having recently completed a segment linking New York, Washington, D.C., Atlanta, Houston and Dallas, some 9,300 miles will be active by the end of September 1998.