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Standardizing Flexibility

For fiber optics to infiltrate a significant number of homes, telephone companies need to settle on technical standards. Just such an effort is under way. Representatives of 20 companies-including British Telecom, BellSouth, France Telecom, Nippon Telegraph and Telephone, GTE and SBC-have teamed to devise a Full Service Access Network (FSAN) running from telephone-company facilities to homes and businesses. FSAN has already been accepted by the International Telecommunications Union and could accelerate the deployment of fiber to the home by providing a set of standards for mass-produced transmission equipment. The FSAN architecture covers a range of fiber uses, from carrying signals to neighborhood nodes and business customers to serving individual homes. FSAN could therefore allow fiber to infiltrate the network piece by piece.

That’s important, because fiber is inching its way toward the home. SBC Communications’ $6 billion Project Pronto will bring more than 20,000 kilometers of new fiber cable, extending the optical network to within 2.7 kilometers of most of the homes the company serves. SBC isn’t alone; US West is laying fiber to within 1.2 kilometers and Bell Canada to within 900 meters, says Claude Roman, an analyst at market research firm RHK in South San Francisco.

And even before Dunwoody, BellSouth was routinely running fiber down every street in new developments. By the end of last year, the company had installed a hybrid fiber/copper service for half a million homes. Buried fiber cables run to service boxes that sit like fat, square fire hydrants along the curb, and copper wires fan out from each box to several homes. In Dunwoody, the company is “overlaying” fiber-stringing it in parallel with existing copper wires to homes.

FSAN makes this expansion easier with a design called a “passive optical network.” The idea is to keep costly and sensitive active components, such as transmitters and receivers, on the ends of the system. Instead of directing signals through intermediate switches, the system simply divides the light among as many as 32 output fibers. No components between the central switch and the end of the fiber require electrical power, helping reduce construction and maintenance costs.

Upgrades to an FSAN system should be easy, generally entailing changes only of the equipment at the ends of the fiber. Data speeds can be boosted by dividing fiber capacity among fewer customers. In the longer term, each fiber might carry one wavelength channel per customer-a technique known as wavelength multiplexing (see “Wavelength Division Multiplexing,” TR March/April 1999).

The companies that developed the FSAN standard-among them Lucent Technologies, NEC and Hewlett-Packard-stress its adaptability. Some already are designing products. “We’re developing a system that will provide low-cost fiber access for small to medium business because we think that’s where the most obvious prove-in is for fiber all the way to customers,” says Ed Harstead, who manages fiber-to-the-home research at Lucent. Indeed, fiber-to-the-business sales will help drive down prices of hardware for more cost-sensitive applications-a key to launching home fiber systems. British Telecom and France Telecom, two of the companies behind the standard, are eager to apply FSAN to business subscribers; BT plans to run fibers to commercial districts, with fibers branching among businesses as they would among homes. Nippon Telegraph and Telephone, which has tested fiber to the home and is cooperating with BellSouth, is now concentrating on business customers as well. From a technical standpoint, “it’s difficult to distinguish fiber to the business from fiber to the home,” says Kenji Okada, supervisor of NTT Access Network Service Systems Labs.

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