A small ray of light

Optical devices are making inroads into corporate networks as companies look to multiplex a single fiber link into high-speed channels for applications such as disaster recovery, storage-area networks and high-bandwidth campus interconnects.

Pure optical switches or photonic switches were designed to handle heavy-duty traffic in service provider core networks. And most analysts agree that these wavelength switches, with their terabit capacity and seven-figure price tags, are overkill for corporate networks.

But optical equipment vendors have less-expensive optical-electrical-optical (OEO) switches in their arsenal that do dense wave division multiplexing (DWDM) or coarse wave division multiplexing (CWDM). And with the service provider market in a slump, vendors are focusing their attention on the enterprise market.

Select companies, especially those with large, distributed networks that approximate a small telephone company, are looking to optical switches to extend their private networks, according to optical consultant Ben Peek.

Other companies and educational institutions are going with optical multiplexers to provide high-bandwidth interconnects between buildings and across the metropolitan area. Other requirements that can lead companies to optical interconnects are disaster-recovery plans tied to SANs and "incredibly large data sets to move around," particularly in CAD and video production environments, Peek says.

GMU opts for DWDM

George Mason University in Virginia is using DWDM to help contain costs and provide adequate bandwidth for three campuses. The university recently outgrew the T-3 lines that connected the three sites and replaced them with leased fiber for about the same price.

The university then purchased three Nortel Optera Metro 5200 DWDM switches, which split a light beam into up to 32 protected channels at speeds up to 2.5G bit/sec.

"Putting in DWDM gear looked like an attractive way to get virtually unlimited bandwidth, while retaining our current costs. So we were looking at it as an investment in the future," says Randy Anderson, the school's director of network engineering and technology.

The university currently uses two Gigabit Ethernet channels for intercampus data traffic, an ATM OC-3 channel for videoconferencing, and there also are plans to put voice traffic on an ATM channel, he says.

The state-supported university, which receives an annual allocation for network hardware, spent a total of $260,000 for the three optical devices.

"We have greatly improved response times to central applications, decreased time required for remote backups, and improved videoconferencing reliability and performance," he says.

Pinnacle West, an energy company in Phoenix, also is using DWDM for a bandwidth boost. The company recently bought three Cisco ONS DWDM boxes, according to senior infrastructure engineer Mario Gomez. "We're using an [Enterprise Systems Connector] channel interface to the mainframe, and running Gigabit Ethernet between routers at different facilities," he says. "The idea was to extend mainframe connectivity. It was mainly for redundancy and business continuity through connection to a mirrored site."

Pinnacle also plans to increase its use of IP telephony and IP videoconferencing. Gomez says the DWDM switch provides virtually unlimited scalability. If bandwidth needs outstrip the existing capacity, "just buy another extension card and throw it in there. You go from one gig to 10 gigs," he says.

David Gross, an analyst with Communications Industry Researchers, says DWDM makes sense for customers with high-bandwidth demands. "At the enterprise level, think about why you have a switch or cross-connect in the first place. Ultimately, it's a multiplexing function."

Peek adds that corporate-level optical components offer the advantage of handling multiple line-rates and protocols, making it easier to adapt to changes and to isolate network segments.

Low-cost optical options

A lower-cost approach is to add an optical interface card onto a standard router.

Spring Independent School District in Houston is using Nortel Passport 8600 routing switches with fiber-optic interface cards at each of its 25 facilities. The buildings are linked by point-to-point Gigabit Ethernet connections, according to network engineer Chris Kent.

In addition to the data traffic generated by the district's 5,000 computers, Kent has added IP telephony, videoconferencing and video surveillance channels. The 8600 routing switches, with 64G- and 128G-bit/sec backplanes, average about $30,000 to $40,000, according to Kent.

For Kent's purposes, "optical switching would be wavelength division multiplexing," rather than wavelength switching. And the district is mapping out uses for DWDM and CWDM. CWDM offers bandwidth up to 2.5G bit/sec, while DWDM can scale up to 10G bit/sec.

Overall, CWDM is probably a better match for corporate needs than DWDM, Gross says. " You can buy an eight-channel box for around $35,000 or $40,000. And those prices have been dropping through the floor recently," he says. CWDM has a shorter reach than DWDM and fewer channels, "but for a lot of these enterprise applications, they're going between adjacent building,'' he says.

A small ray of light

Related Links