Sprint executives sever fiber cable to demonstrate self-healing network

Sprint executives sever fiber cable to demonstrate self-healing network

George Kotelly

To dramatically accentuate the nearly immediate restoration properties of a fiber-optic ring synchronous optical network, Sprint executives deliberately cut the long-distance carrier`s operational fiber cable in Chicago. This cable site was selected because it represents Sprint`s first Sonet ring network to enter commercial service.

Using an ax for emphasis, the executives split the cable, on cue, in front of media witnesses. The company`s 4-fiber, bidirectional, line-switched ring network blinked momentarily on an adjacent television monitor set up to electronically capture the disconnection. As expected, network service continued without noticeable interruption, despite the cut cable.

The seemingly instant restoration capability derives from the survivability properties of Sonet fiber-ring networks. In this network architecture, fiber cuts go unnoticed for voice calls. Even video transmissions experience only a quick flicker of a few tens of milliseconds in duration. Data transmissions generally run without any loss of information.

"Survivability is the key," declares George Fuciu, Sprint senior vice president, network and information services. "In the event of a fiber cut or an electronics outage, service is restored in milliseconds, not minutes." In fact, transmission traffic is rerouted in as fast as 60 milliseconds.

To demonstrate company confidence, Sprint is planning as many as 39 Sonet ring networks for operation throughout the United States by mid-1996. The entire nationwide network infrastructure will employ self-healing capability.

Sprint`s ring design markedly contrasts with linear Sonet networks. In linear networks, service halts when traffic traveling from point A to point B is interrupted. Network managers must resolve the problem and then administer the physical restoration process, which is a time-consuming effort. On the other hand, traffic on a survivable ring network is redirected automatically on a preplanned alternate route when a system failure occurs.

"Many customers will be running broadband mission-critical applications over distributed computer systems. The most reliable survivable network is a must for these customers," says Kevin Baker, president, Sprint business services group.

Fuciu contends that before the Sonet survivability ring design, customers had to endure delays in service restoration of five to 20 minutes. "The state-of-the-art in the telecommunications industry involves electronic restoration through preplanned alternate routing built into network management computers," he adds.

Of course, after a fiber cable is cut, it still must be manually repaired--this can take minutes or hours, depending on the installation circumstances. "We will repair any cut fiber as rapidly as possible, but customers will be able to continue their network operations undisturbed while repairs are made," says Fuciu.

The two major Sonet equipment suppliers for Sprint networks are NEC America Inc. in Melville, NY, and Alcatel Network Systems Inc. in Richardson, TX. q

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