Fiber rides free on Bay subway

Jan. 1, 1995

Fiber rides free on Bay subway

George Lawton

The San Francisco Bay Area Rapid Transit system has announced a plan to build an 82-mile fiber network throughout its subterranean tunnels at a cost of $44.5 million. The network will be built through a novel financing plan bankrolled by Pitney Bowes and integrated by MFS Network Technologies, Omaha, NB. Once completed in 1997, BART will have a state-of-the-art fiber-optic network for its own use, without putting any of its own money into the project.

The network will be rolled out in stages. The first, and perhaps most important one, will be the trans-bay tube segment that connects San Francisco and Oakland under the bay. This is expected to be pulled by Valentine`s Day and will begin carrying commercial traffic by July.

As part of the deal, MFS Network Technologies gets the lion`s share of the contract ($38.5 million) to design and build the fiber network, as well as an 800-megahert¥radio trunking system designed for underground access. MFS will install one 4-inch conduit throughout the subway that contains four 1-inch innerducts. Each innerduct will carry 48 fibers, for a total fiber count of 192 fibers throughout BART.

BART will use one of the innerducts for its own use. MFS Network Technologies will manage the innerduct after it is built and lease the three conduits of dark fiber to interexchange carriers, competitive access providers and any other interested parties. Ninety-one percent of the lease revenues will go toward retiring the debt for the next 15 years, and will then go to BART. For its role in the venture, MFS will get the remaining share.

"There have been other subways that have put in a limited amount of fiber for their own internal use, but this marks the first time fiber optics technology has been integrated with a comprehensive revenue generating system," says Bob Eide, vice president at MFS Network Technologies.

According to Margaret Pryor, president of the BART Board of Directors, "This was an historic agreement, not only because it has created the template for future public-private partnerships on a national scale--the linking of public assets with private capital--but it is historic for another reason: It expands BART from the business of simply moving people to the realm of moving data and ideas."

When asked why ventures like this have not been undertaken in the past, Eide responds, "In any project like this, when you are working with a public agency, they have different rules than private businesses. Also, because it has never been done, there is no blueprint to create all the components into one project. BART has a great vision and they are far thinking in its approach and what it wanted to accomplish. That made all the difference in the world."

Network applications

BART currently uses coaxial cable and twisted-pair cable throughout the metro for all of its data networking needs. BART`s fiber network will replace this network, as well as enable a number of new applications. For starters, it will improve the management of the thousands of fare machines throughout the metro by enabling them to communicate their status in real time.

The fiber will also support an 800-MH¥radio trunking system. Wireless nodes above ground and in stations will be connected together via fiber. In addition, a "leaky" coaxial cable developed by Andrew Corp., will be pulled throughout the tunnel system. The leaky, or radiating, coaxial cable, consists of a conducting core surrounded by dielectric material. Its outer conductor contains holes through which the radio signal leaks. This coaxial cable acts as an antenna, enabling radio communication throughout the subway tunnels. It will initially support only BART personnel, police and firefighters. Eventually it will be used to support a public telephone service onboard the BART trains.

The fiber will not just move more information; it will also help to move more trains. The BART trains are almost entirely computer controlled. The location of every train is determined by a network of sensors throughout the subway. However, because of the limited telecommunications capacity of the existing copper, the network can only locate trains to within a 1500-foot-long section.

This limits the spacing between the trains and imposes a significant bottleneck to additional capacity. The most problematic spot is the trans-bay tube, which is fed traffic from three separate train lines in the East Bay. Current train control technology at BART limits train frequency to every 3.75 minutes, and thus, the capacity of the trans-bay tube to 60,000 people each rush hour.

The federal government has recently announced the award of $19.5 million in defense conversion funds to an alliance of BART, Hughes Aircraft and Morrison Knudsen Corp. to develop an advanced automated train control system that will significantly increase the frequency of BART trains and the system capacity.

The network will be based on global positioning technology that traditionally operates only in the open air because of the limited penetration of the radio signals from a satellite source.

Once the prototype is completed, BART will be able to nearly double train frequency and capacity to approximately 120,000 people through the trans-bay tunnel each rush hour. This is particularly significant on the eve of a plan to triple tolls on the Bay Bridge during rush hour--the only bridge between Oakland and San Francisco.

The entire network will pay for itself many times over, compared to the estimated $2 billion required to build a second trans-bay tube. Improved train monitoring will also lead to improved electrical efficiency, according to Ron Rodriguez, a BART spokesman. BART currently pays more than $20 million a year to power the trains.

This may hail the beginning of a $1 billion market for the technology in the United States alone. Within the next decade, New York, Philadelphia, Washington, DC, Baltimore, Boston and Atlanta are planning upgrades and extensions that could use equipment tied together by fiber. q

George Lawton is a freelance writer based in San Francisco.

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