Nice article on metro dwdm from
DATA COMMUNICATIONS June 1999 By Andrew Cray
DWDM: In for the Short Haul?
The promise of just-in-time provisioning makes now the time to assess metro DWDMs
data.com
<thank's to ULYSSES at raging bull for finding this article>
Some highlights:
Right now, there are five vendors poised to take advantage of that market: Ciena Corp. (Linthicum, Md.), Ericsson AB (Stockholm, Sweden), Northern Telecom Ltd. (Nortel, Mississauga, Ontario), Sycamore, and Osicom Technologies Inc. (Santa Monica, Calif.) (see Table 1 data.com ). Long-haul DWDM vendors Alcatel S.A. (Paris) and Lucent Technologies Inc. (Murray Hill, N.J.) plan to ship metro devices later this year. And startup Optical Networks Inc. (ONI, San Jose, Calif.) says it has a DWDM product set for beta shipment in August.
....
Plug and Pay Less
As for provisioning services, carriers can tackle the task two ways. They can bring circuits to customers either directly on top of wavelengths, or they can carry them using current Sonet gear.
In the first scenario, customers just plug their equipment into the DWDM, and each of the services they use travels natively over a 2.5-Gbit/s wavelength, with multiple wavelengths used to provision multiple services. In the second scenario, carriers connect a DWDM to a
Sonet ADM. Customers plug their equipment into the ADM instead, using its multiplexing capabilities to break down the 2.5-Gbit/s wavelength into several lower-speed services, like T3s (45 Mbit/s) and OC3s.
Whether one approach is better depends on the service being sold. Splitting wavelengths means "you don't have to waste a whole wavelength for a relatively low-speed signal," explains Ron Mackey, Osicom's executive vice president of technology. But big-bandwidth apps work at such high speeds there's no need to multiplex them down, so they're better handled without additional Sonet equipment, says Steve Chaddick, Ciena's senior vice president of strategy and corporate development. He thinks any service above OC12 is delivered more efficiently on top of wavelengths. Then again, carriers might want to keep their Sonet add-drop multiplexers and use them in conjunction with a DWDM. "Sonet is something CLECs and RBOCs have lived and breathed for a long time, and they love it," Weingarten says. Most of today's DWDM products, he adds, don't offer nearly as much as Sonet in terms of configuration, restoration, or management.
Osicom, however, says its Gigamux may offer the best of both methods. It has so-called EPC (electrical photonic concentration) cards that split each wavelength into 16 lower-speed pipes supporting such services as DS-3, OC3, fast Ethernet, and FDDI. Baksheesh Ghuman, senior product manager at Electric Lightwave Inc. (Vancouver, Wash.), a CLEC that has been testing the product, says that's made for a 20 percent savings over a Sonet ADM. What's more, the Gigamux bundles everything in a single device, making it easier to manage. "Service providers like solutions," says Deb Mielke, an independent consultant at Treillage Network Strategies Inc. (McKinney, Texas). "They don't like to have to put everything together all the time." But Osicom's multiplexing scheme is different from Sonet's, so carriers may need to retrain their engineers in order to do that management. |
