Lambdas on the loose: New DWDM hybrids take a shot at the metro market

Dense wave division multiplexing is an easy sell for long-haul services. But for short-haul metropolitan area networks, DWDM is not such an easy fit.

DWDM has won carriers' hearts as a transmission method with its proven ability to pump bandwidth over long distances. But the clogged metropolitan networks are not demonstrating to be as fruitful for DWDM for a variety of reasons - primarily cost and the technology itself. The major problem with bringing DWDM to metropolitan areas lies in DWDM's origin. Invented to increase bandwidth on long-haul networks, DWDM usually carries 2.5 Gb/s on each wavelength on point-to-point networks.

As with long-haul networks, every node in a metro ring must support DWDM even if only a few customers need additional bandwidth. That lack of flexible add/ drop configuration necessary to manage the dynamic metropolitan traffic patterns escalates re-engineering costs and potentially pushes providers to reconsider fiber outlays, according to Dawn Hogh, vice president of marketing for Kestral Solutions.

Vendors have spotted this void in bandwidth-hungry metropolitan areas and are developing hybrid or altered versions of DWDM that are tailored to the specific needs of the short-haul environment. The hybrid products are trying to address the pricing and technology constraints that leave the metropolitan market underserved.

"It can run $75,000 to in the hundreds of thousands to pull fiber through an area like Manhattan," said Peter Tierney, president and chief operating officer for Millennium Optical Networks, a New York-based competitive local ex-change carrier. Millennium is building a metro DWDM system in New York with the help of Sycamore Networks, instead of incurring the exorbitant expense of laying fiber for more Sonet rings. "If it were Las Vegas, it wouldn't make sense to go this route, but for areas like Boston, London and New York, it does," Tierney said.

Millennium will use Sycamore's SN 8000 intelligent optical add/ drop multiplexers (ADMs) to deliver capacity to carrier hotels on a timely basis. Millennium will provide "liquid bandwidth," which means that it will have high-capacity provisioning at a fast rate, Tierney said. Service providers will plug straight into Sycamore's DWDM platform, which provides transport, switching and routing all in one box. The Sycamore gear also is integrated with Sonet and SDH features, making it easy to bring into existing infrastructures, said Bill McCullen, director of product marketing for Sycamore. That capability will enable Millennium to serve European carriers when Millennium's network is turned up in about two weeks, Tierney said. "[European carriers] can maintain things such as performance management and protection switching, which they typically lose when they have to switch to a Sonet system at a local carrier."

But Sycamore is not alone in its efforts to serve the metropolitan market. Vendors such as Ciena, Corvis, Optical Networks, Osicom Technologies, Qeyton Systems, Quantum Bridge and Tellabs, as well as larger vendors such as Lucent Technologies and Nortel Networks (see sidebar), all have strong showings in the area - and more are coming.

Many companies are focusing on the metropolitan area, each with a slightly different way to solve the same problem, said Frank Dzubeck, president of Communications Network Architects. One start-up, Chromatis Networks, is developing a variation of DWDM called selective WDM (SWDM) (Telephony Sept. 27, page 32). Traditionally all nodes on the Sonet ring must upgrade to DWDM to support the service, but selective WDM will vary depending on need, and only the sites requiring more bandwidth will have to upgrade. High-bandwidth locations use a dedicated wavelength in the 1550 nm band, whereas low bandwidth sites will share the 1310 nm Sonet ring.

SWDM will create two rings on the same fiber, said Doug Green, vice president of marketing for Chromatis. "In the metropolitan area, unlike long haul, it is not just about passing wavelengths. Sonet just can't grow fast enough to keep up with demand," he said.

The growing trend is to add more functionality into less equipment, so Chromatis is collapsing the ATM, IP or time division multiplexing (TDM) router and WDM equipment into the same box. Chromatis' SWDM supports low and high bandwidth needs and the ability to upgrade to DWDM more cheaply, Green said. "As the network grows, this allows you to [add DWDM] when and where you need it - for less money."

Another start-up trying to pry open the metropolitan market is Kestrel Solutions. Kestrel is combining the elements of three different technologies to form one metropolitan hybrid, called optical frequency division multiplexing (FDM). The multiplexing technology uses a mixture of FDM, digital signal processing and optical modulation. Like the other players, Kestrel's solution will meet the high capacity needs of the metropolitan area while reducing costs, company officials say. Kestrel's optical FDM will work over essentially any fiber and any protocol, said Hogh. By doing that, Kestrel can address legacy environments along with newer technologies.

Hogh compared optical FDM with cars on a highway. "Where TDM increases capacity by increasing speed and WDM increases capacity by increasing the number of lanes to pass traffic through, optical FDM increases capacity by putting more passengers in each car and increasing traffic density."

Kestrel is developing an optical ADM, called the TalonMX, to be based on the optical FDM technology.

Start-up Astral Point Communications also is trying to clear the metropolitan clog. The company is focusing on helping carriers transition from S onet legacy networks to the converged world of IP without a forklift upgrade, said Bill Mitchell, vice president of marketing for Astral Point. By providing a multiservice network, Astral Point intends to lower the equipment's first cost and address power and space constraints.

While the lack of capacity in the metropolitan area appears to be food for start-ups and well-established companies, larger equipment vendors are trying to ensure that they don't get locked out.

Nortel Networks acquired Cambrian Systems in 1998 as an entry into the metropolitan market and is marketing its OPTera Metro products.

More recently, Cisco Systems' move into optical networks has been obvious with its acquisitions of Cerent and Monterey Networks. But Cisco has left a void in its metropolitan offering, which it currently fills through an agreement with Ciena.

Lucent Technologies is taking a multipronged approach to the metropolitan area to attempt to meet the different service needs, said Kathy Szelag, vice president of marketing for Lucent's optical networking group. It is offering several products under its WaveStar optical umbrella, such as the WaveStar MetroPoint, WaveStar AllMetro and OpticAir systems.

But Lucent has the upper hand in the market, Szelag said. "There are a lot of players in the market, and, in theory, any of us can deliver the same service - the question is at what cost. It really comes down to price," she said.

Products will sell based on their functionality and cost, which leaves the door open for smaller players, said Michael Howard, principal analyst at Infonetics. "The more functionality you put in the box the better," he said.