Lucent unveils terabit dwdm system

By STEPHEN HARDY

Are you ready for another buzzword? Lucent Technologies, Murray Hill, NJ, hopes it has added "ultra-dense wavelength-division multiplexing" to the fiber-optics lexicon through the announcement of a dense wavelength-division multiplexing (dwdm) system with a maximum capacity of 3.2 Tbits/sec. The system, dubbed WaveStar ols 400G, delivers five times the bandwidth of other presently available systems, claims the company.

The WaveStar ols 400G, the latest in Lucent`s family of Optical Line System (ols) products, will transmit 400 Gbits/sec--the per-second traffic of the entire Internet, according to Lucent`s estimates--over a single fiber. As initially offered, the system will accommodate up to eight fibers running at that rate.

The Bell Laboratories-developed dwdm system will enable carriers to upgrade capacity from one channel to eighty in increments of two, according to Harry Bosco, chief operating officer of Lucent`s Optical Networking Group. The high- capacity resident within the system, combined with this flexible upgrade ability, translates into a potential savings of 40% in equipment costs over the use of lower-capacity, less flexible systems, he says.

In addition to the wide range of channels, the system also presents other unique advantages, according to Lucent. These include the ability to mix 2.5- and 10-Gbit/sec Synchronous Optical Network/Synchronous Digital Hierarchy (sonet/sdh) traffic over a single fiber and to support sonet/sdh equipment from multiple vendors operating at these mixed rates (see figure on page 1). The system also will accommodate Asynchronous Transfer Mode and Internet protocol traffic.

Carriers will be able to add and drop traffic in both fixed and selectable increments.

The key to achieving the high bandwidth is maintaining wavelength integrity within the confines of 50-GHz channel spacings within the C band, an amount half that of the 100 GHz recommended by International Telecommunication Union standards. Lucent sources cited planar waveguide and externally modulated laser technology developed by Bell Labs and fielded for the last two years as contributors to the new dwdm capacity standard the system represents. In addition, the ability of the system`s wideband amplifier to accommodate the 2.5- to 10-Gbit/sec spectrum enables the mixed-rate transmissions that promise to be one of the system`s major selling points. The optical amplifiers that are part of the system feature automatic gain control, which enables carriers to add wavelengths without having to manually adjust the amplifiers.

The system is designed to be as open as possible to accommodate a variety of network configurations. This openness includes fiber. "This is designed to work on standard fiber, which is 90% of the fiber out there globally, or on high-performance dispersion-compensated fiber like TrueWave Positive. No dwdm system works very well on the very old dispersion-shifted fiber--but there`s very little of that out there," according to Kathy Szelag, director of strategy at Lucent`s Optical Networking Business.

The system`s terabit capacity represents more than technological one-upmanship, according to Bosco. "There`s a lot of capacity here, but carriers know they`ll need it," he says. "They`re asking for it. For example, ISPs [Internet service providers] are reporting traffic growth today of more than 15% a month. On carrier networks, this 15% translates to 80% growth in data traffic per year." Bosco predicts that the adoption of digital subscriber line technology in copper-based local access networks also will lead to further demands on the backbone networks in which the WaveStar dwdm system should see its first applications.

Those initial applications could come as early as the first half of 1999, as at&t has already announced its intention to trial the new dwdm equipment in its test facilities during the fourth quarter of this year (see "at&t pushes sonet and dwdm network upgrades," page 22). These trials will coincide with Lucent`s plans to make the WaveStar ols 400G commercially available at roughly the same time.

Besides testing the system`s basic operation, at&t will face the challenge of integrating the system with other equipment already in its network, as well as with its network management system. Integrating the new dwdm system with sonet/sdh equipment of other vendors is a "no brainer," in the words of Szelag, as such interoperability has already been demonstrated with Lucent`s previously released 16-channel ols. However, while the WaveStar system will be compatible with other Lucent ols equipment (in fact, the 16-channel system will be able to be upgraded to 40 and 80 channels, to equal the WaveStar wavelength capacity), it will not be interoperable with dwdm equipment from other vendors.

In differentiating the WaveStar system from the offerings of other vendors, Szelag says that nearly all commercial systems available today operate at a maximum of 80 Gbits/sec over a single fiber. This 80-Gbit/sec total usually is achieved either by a combination of eight 10-Gbit/sec streams or thirty-two channels of 2.5 Gbits/sec. Some vendors have announced systems that will provide thirty-two channels transmitting at 10 Gbits/sec. However, Szelag pointed out that this equipment still will not match the 400 Gbits/sec offered by the WaveStar.

The dwdm system represents the first of what is anticipated to be a family of WaveStar products. Subsequent systems, expected to be announced in the first quarter of this year, will focus on bandwidth management and reducing the number of elements in a typical network, according to Lucent sources. q