DWDM uses existing network: Seminole County secures quick, economical solution to outgrowing its municipal telecom infrastructure - Special focus: optical technologies - dense wavelength division multiplexing

Communications News, Dec, 2003 by Robert Pease

Seminole County, Fla., -- recently came to a crossroads with its telecommunication infrastructure. Its existing network could no longer support the growing requirements for bandwidth and speeds associated with new technologies for voice, data, video, LAN and WAN services. It was time to seek a solution that would be cost-effective, scalable and easily integrated with existing equipment.

Seminole County's existing network, installed in the early 1990s, consisted of a 10-node OC-3 (155 Mbps) ATM synchronous optical network (SONET). The system supported W-I voice and 10 Mbps Ethernet transport integration on one platform. A Nortel Networks Magellan Passport system provided the WAN backbone over the county's nearly 250 mites of fiber-optic cable. At each node, the data entered the LAN through Cisco Systems components.

The network serves approximately 5,000 users, including 1,400 county employees and various city and government offices. When new applications were demanding more of the network, county stall and officials decided to look into possible solutions for expanding network capabilities to meet and exceed the demands of its users.

The county strategically determined where the most need was for increasing bandwidth and connectivity and decided to focus the upgrade on three main locations. The county services building, the sheriff's office/public safety facility and the Oxford Library formed a fiber ring approximately 60 kilometers in diameter, and would provide centralization for the project. The "why" and "where" were now determined for the project but questions still remained for the "how" in creating a network that would meet the county's future communications needs.

"We were at a crossroads and didn't really know what to do," says Greg Holcomb, information technologies manager for Seminole County. "We knew that increasing the county's physical fiber plant was unrealistic considering the huge expense of deploying more fiber in the streets for direct connectivity.

"We'd already done some research and were kind of leaning toward a DWDM (dense wavelength division multiplexing) solution, but it was a brand new application for us. We were a little bit skeptical about some of the information we were getting back from different vendors and manufacturers.

"Our request for proposal actually left out any specific solutions and just stated that we wanted to increase our network and get more capabilities out of our existing fiber," adds Holcomb. "We received three proposals in response from Nortel Networks, Cisco Systems and ADVA Optical Networking."

"Only one proposal came back stating we could use exactly what already exists, interface with both the Cisco and Nortel equipment, and get more bandwidth out of our existing fiber plant," says Holcomb. "ADVA offered its FSP 3000 solution, a modular DWDM system, claiming it would slide nicely into our network and enable us to get the speed and bandwidth we required in minimal time."

"What we were able to do was to move off of some of the components," says Holcomb. "For example, our Ethernet connections on the Passports were 10 Mbps, so we quickly pushed our connectivity speed to gigabit. But we plugged it directly into the Cisco equipment, rather than through the Passport, because the Passport wouldn't support the Gigabit Ethernet connection. It enabled us to push some of the applications off the slower boxes to take' advantage of the higher bandwidth."

Although the key features of the ADVA solution were its expandability and low cost to implement, there were some challenges. The biggest obstacle faced in implementing the new platform was in having to use the existing fiber for the actual cutover operations.

"We were moving fiber strands between the street and the Nortel box to the ADVA box, and we had to keep the existing system running while implementing the new system," says Holcomb. "Establishing quality of service on the lower bandwidth sides was also challenging, since none of the previous applications required high speeds and true quality of service. All the transmission characteristics previously used in this part of the network were fairly sloppy prior to the upgrade."

The system never had to go offline during the entire cutover process. The original design of the Passport network used two fiber strands in every box, providing a redundant ring. Using the redundancy of the network, the ADVA nodes were brought online first, and then the Pass port system was connected to the ADVA nodes to ensure everything was communicating properly. Finally, everything was transitioned to the other strand to make the ADVA strand the primary link and the Passport strand the secondary link.

In terms of cost and return-on-investment issues, Holcomb says the upgrade paid for itself as soon as it began operating, when compared to the cost of installing roughly 60 kilometers of new fiber in the streets.

"From a time perspective, it was also advantageous," says Holcomb. "We were probably looking at two months to a year to lay 60 kilometers of fiber after all the front-end work, installation and purchase. But we literally implemented this solution in two weeks, which saved us a tremendous amount of time and allowed us to take advantage of the bandwidth right off the bat.