French fiber-optic network trials gain definition

French fiber-optic network trials gain definition


France Telecom has tapped four fiber-optic access network suppliers for its 1997 trials of fiber-to-the-building/curb, or FTTB/C: Alcatel, SAT, MET (Matra-Ericsson) and Siemens S.A., all based in Paris. Details of the suppliers` proposals are becoming defined. Dominique Chapelain of France Telecom, responsible for optical access networks in these upcoming trials, cautions that because the contracts are not completely defined or signed, the France Telecom technical selections are not "immutable" and could evolve.

The trials, known as DORA in French, are for fiber-optic deployment in the access network. The goal, emphasizes Chapelain, is "to experiment with the introduction of multimedia services and to measure the operational impact of a certain number of lines on the organizational operations of France Telecom." The results may determine the best architectures to use in a full-scale deployment.

DORA is one of the projects named by the French government as a "first tier" information superhighway project, and is therefore receiving substantial government support. It is expected to serve as the basis for multimedia services and video-on-demand up to Motion Picture Experts Group-2 rates of 6 megabits per second, as well as telecommunications and cable-TV services for residential and small business customers (see Lightwave, November 1995, page 1).

While precise information on the costs is not available, an unconfirmed estimate is 550 million French francs (US$100 million). Other estimates include US$200 million in pilot services based on fiber-optic network technology.

"In France, as in the rest of Europe, the fabric of the land is fundamentally different from the United States, with a primarily urban component for residential housing, as opposed to large residential estates in North America," notes Chapelain. "This may have a significant impact on the selection of optimum architectures. Moreover--again as a result of the housing structure in France--small businesses such as those belonging to shopkeepers and doctors are entirely accommodated in residential areas, making it necessary to consider their needs at the architectural stage."

Another challenge to implementing a new architecture is the history of cable TV in France. Originally, France Telecom was charged with developing cable TV. Now, other operators can build networks and offer cable-TV services as well. However, France Telecom still owns a substantial percentage of the networks and in many places is both the owner of the infrastructure and the service provider. This means it has to develop an architecture that can accommodate both areas in which it holds the cable-TV franchise and others where it is strictly a telecommunications provider.

Four lightwave networks

The DORA trials cover fiber-to-the-building/curb networks in four cities: the Left Bank of Paris, Bourges, Narbonne and Rennes. Each supplier will be assigned a city, and each city`s trial will cover 10,000 subscribers (with a possible extension to an additional 10,000 subscribers per city). But which supplier gets which city is a closely guarded secret.

Fiber-network deployment is expected to take place in 1997, following a short pre-trial approval process. Although the overall solutions are similar, they vary not only in the equipment supplied by the different groups, but also in the upstream and downstream bit rates employed. Furthermore, whereas Alcatel, SAT and MET may provide solutions incorporating both broadband telecommmunications and cable TV, Siemens can provide only a broadband telecommunications solution.

This decision was made by France Telecom not because Siemens is unable to provide cable-TV service but to allow Siemens to explore solutions in areas where it only offers telecommunications services.

The four suppliers have disclosed some preliminary information about their proposals. MET`s solution may cover 10,000 to 20,000 subscribers per switch center, explains Daniel Friedman, the company`s director of fiber-optic access networks.

In the MET network, signals received from the multimedia server and the telephony switch will be merged with an asynchronous transfer mode, or ATM, crossconnect switch. The fiber structure from the switch to the building may split a single fiber in a 1:16 branching switch. Downstream and upstream signals will run over two different fibers, with a downstream passive optical network bit rate of 1 gigabit per second and an upstream rate of 190 Mbits/sec. ATM cells sent over the fiber-optic network to the optical network unit may be extracted and converted to electrical signals for delivery to the building. Video distribution is provided through amplitude modulation-vestigial side- band transmission over fiber (with the same cable and split ratio as telephony and multimedia) to another optical unit in the building.

Future-proof solutions

"France Telecom has accepted a solution that should be future-proof," Friedman explains. The fiber-optic cable will be supplied by Acome and installed by Entreprise Industrielle.

The SAT solution is based on the fiber loop access technology developed with Broadband Technologies. But while this system has been supplied to U.S. customers such as Bell Atlantic and SBC Communications Inc., SAT has reworked the system to observe European standards and to develop additional functionality, explains Guy de Passoz, executive vice president of marketing and strategy for the telecommunications division.

Under the SAT solution, each optical line terminator can handle 16 fibers, and each fiber can be split-divided into eight lines. Depending on the geographic dispersion of the subscribers, 12 to 60 lines can be served by each of the 128 optical network units, for a total of 2000 subscribers.

Downstream bit rates may run to 51 Mbits/sec; upstream rates may be 1.62 Mbits/sec. Silec, which is a sister company to SAT under the Sagem group, may supply its special "microgain" fiber, which the company says is specially adapted for access networks.

The product architecture proposed under the Alcatel solution, known as 1000AN, can serve 12,000 to 15,000 subscribers per optical distribution access node, explains Bernard Vaslin, sales manager at Alcatel CIT. It is a fully ATM solution from the access node down to the customer premises, where the final drop uses copper in the building for multimedia services. Downstream data rates will run to 25.6 Mbits/sec, with large upstream capacity in the range of 1 Mbit/sec. Cable TV will be run over separate cables. This platform expands the scope of earlier developments put into service in several countries. Great Britain and Germany employ scales of a few hundred lines--as in the BT-IMS and the Baden Wurtenberg and Berlin multimedia trials--to several hundred thousand lines--as in the Hytas/OPAL telephony-only trials. However, France is the first to experiment on this level," Vaslin says.

The Siemens solution for telecommunications and multimedia marks the company`s first major win with France Telecom. "It`s a great achievement," says Francois Gerin, director of the French subsidiary`s telecommunications division. The challenge was to design a system that could act as an interface with the existing network for integrated services digital network and "plain old telephone service" and support leased lines and future multimedia applications. The Siemens system will enable a personal computer with a high-speed modem to send and receive data using the Digital Audio-Visual Council standard, which will transmit 1.5 Mbits/sec upstream and 12 to 51 Mbits/sec downstream over the public network. It is also able to multiplex thirty 64-kilobit-per-second telephone lines over a single pulse code modulation line, explains Gerin.

The granularity (number of customers served per optical network unit) has yet to be defined by France Telecom. While parts of this system are derived from those supplied to Deutsche Telekom for the Opal narrowband project, "This is the first large-scale project integrating these technologies," concludes Gerin.

In addition to the DORA program, France Telecom is also running other smaller trials. Among these is a field trial in the city of Lannion (also the site of a major France Telecom research facility).

"As we move toward the multimedia world, the final strategy of France Telecom may probably be a `cocktail` of different but complementary access network technologies, such as [fiber-to-the-building/curb, asymmetric digital subscriber line] and maybe in some cases [hybrid fiber/coaxial-cable networks]. But the core of multimedia service provisioning will certainly be based on ATM end-to-end use from the server to the set-top box," says Chapelain. q

Adele Hars writes from Paris.

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