nec trials 32-channel dwdm system with carrier

By GRACE F. MURPHY

Nec America Inc., Herndon, VA, has deployed a 32-channel dense wavelength-division multiplexing (dwdm) system with optical add/drop capabilities in a customer lab for trial evaluation.

The company would not name names, but says a "major" interexchange carrier began testing its SpectralWave dwdm equipment in September 1997. nec America claims to be one of the first companies to enter a fully configured 32-channel dwdm system for exclusive customer evaluation.

The trial SpectralWave system is scheduled for network deployment in the first quarter of 1998, provided tests are successful, according to Steve Cortez, the product planning manager for the transport product management division of nec`s wavelength-division multiplexing (wdm) product line.

Cortez says the product`s biggest value is that carriers can remotely access 100% of the 32 wavelengths and provide add/drop capabilities at selected sites. Cortez compares the architecture to what nec is implementing for wdm in Rochester, NY-based Frontier Corp.`s telecommunications network but with the addition of add/drop functionality.

The SpectralWave system is designed to work with standard singlemode fiber and can be used to build a large-capacity, long-distance optical transmission system for carrier applications. The system multiplexes and demultiplexes up to 32 OC-48 (2.5-Gbit/sec) channels into a single optical fiber using narrowband wdm technology. The result is 80 Gbits/sec of throughput.

In accordance with emerging International Telecommunication Union recommendations and application codes for optical networking, the system multiplexes an optical signal, "boosts" it to a transmission line rate, then transmits it up to 80 km without amplification. With the deployment of up to four inline optical amplifiers, the SpectralWave system allows up to 400 km of long-distance transmission.

Cortez says that nec chose an open architecture design so that the system can interoperate with any Synchronous Optical Network multiplexing system that provides an OC-48 signal.

"We`re going after markets with embedded products already there," he says in further explaining the company`s choice of open architecture design. "Customer requirements mean being able to provide a more open architecture and more flexibility."

The add/drop capabilities are intended to allow carriers to drop or add channels at an optical amplifier site without interrupting the other channels.

Robert Gadient, a senior consultant at the market analyst firm Ryan, Hankin, Kent in San Francisco, CA, says 32-channel dwdm systems with add/drop capabilities are already being offered by some companies and will become increasingly common. Besides being efficient, such systems also reduce terminal equipment costs.

"I think every company that builds a dwdm system is going to have to provide fiber-optic add/drop multiplexers," he says.

ciena Corp., Linthicum, MD, made a splash at the February 1997 Conference on Optical Fiber Communication with its MultiWave 1600 Optical Add/Drop Multiplexer. Other companies have followed suit.

Cortez anticipates that dwdm technology will continue its evolution from first-generation, point-to-point systems whose main purpose was to meet increasing demands while dealing with limited fiber-pair availability. With the add/drop component, the systems are more active in the network architecture, and the next step will be evolution to provide other ring services, he says.

Gadient sees the dwdm optical add/drop multiplexing systems becoming more flexible in the future. Rather than having to drop the first four or six channels of traffic, carriers will have more precise selection ability once optical switching comes to the fore, he says. q