Quad-WDM technology hikes MCIs network capacity

Quad-WDM technology hikes MCI`s network capacity


Deployment of four-wavelength, wavelength-division multiplexing (quad-WDM) fiber-optic technology by MCI Communications Corp., Washington, DC, quadruples the capacity of existing backbone networks. Currently, MCI`s backbone network operates at 2.5 Gbits/sec, but quad-WDM increases that capacity to 10 Gbits/sec, enabling 64,500 simultaneous transmissions.

Quad-WDM technology is expected to be deployed in the third quarter of 1996 on an MCI-network route between Washington, DC, and Richmond, VA. With quad-WDM, a single optical fiber accommodates four light signals, instead of one, and routes them at different wavelengths through the use of narrowband WDM equipment.

This technology resulted from a collaboration between MCI and Marlborough, MA-based Optical Corp. of America (OCA), which provides quad-WDM devices. MCI is using quad-WDM technology to quadruple its network capacity without the expense of adding fiber-optic lines.

Fred Briggs, chief engineering officer at MCI, says, "Quad-WDM increases the power of our network engine by addressing these capacity needs without the additional cost of new fiber. This technology is particularly valuable in major metropolitan areas where the company is experiencing growth in voice and data traffic."

With this technology, lightwaves can be transmitted in two directions over a single fiber. Two signals are sent through a single fiber at 1533- and 1541-nm wavelengths to their destination, where they are separated and sent to receivers. From the receivers at the opposite end, two signals are transmitted back at 1549 and 1557 nm. Transmitting two wavelengths in each fiber increases total capacity (see figure).

Multimedia applications

The additional bandwidth provided through quad-WDM, allows MCI to offer an array of multimedia applications, including those developed through its HyperMedia product line. One HyperMedia service targets the television-broadcast industry. Currently being tested by NBC, the service enables affiliates to access video content on-demand through servers based in MCI`s network.

As the quad-WDM project is deployed along major traffic corridors, MCI is expected to be able to offer users more wide-area bandwidth at lower rates, introduce high-capacity services and provide additional emergency back-up capacity. MCI has been installing self-healing fiber-optic Synchronous Optical Network (Sonet) rings around major cities for the extra capacity it needs to handle major network outages (see Lightwave, June 1996, page 3). The MCI network upgrade with quad-WDM technology should also help satisfy the exploding need for high-speed Internet access. In April, the company upgraded its Internet backbone from 45 to 155 Mbits/sec.

An industry analyst sees quad-WDM as a solution for network traffic jams. Joseph Blaylock, vice president and research area director for the Gartner Group in San Jose, CA, also views what MCI is doing with quad-WDM as half of the solution. The other half of the solution "is for MCI to have back-up capacity to recover from fiber cuts," Blaylock says. "For the past two years, MCI has been dealing with the lack of capacity in its network. Quad-WDM is a move in the right direction."

Grant Draper, marketing services director at Probe Research in Cedar Knolls, NJ, thinks WDM promises to slash transport costs and impact every carrier`s competitive positioning. "It was Probe`s experience before the MCI announcement that Asian and European optical component manufacturers and system integrators were positioning themselves to be the first to capitalize on the fundamental technology advancement WDM offers," Draper says.

"Many of them indicated that they were or would be aiming their sights directly upon AT&T and Northern Telecom`s lucrative OC-12 and OC-48 markets," he recalls. Draper says that WDM has the promise to fundamentally shift the economics of transport, by driving down the costs of delivering multimedia and video-transmission services by as much as 75%. q

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