Faster, More Reliable Than Satellites : Undersea Cables Still the Best Way to Communicate Across the Seas

In a remote underground bunker on the Rhode Island coast, George Benford listens as thousands of telephone calls flood in from across the Atlantic.

But all he hears is silence--that is, unless something goes wrong with either of two 3,500-mile submarine cables that begin about 25 feet from his desk and end in France and Spain. Then, bells go off and the phone starts ringing like a firehouse during a five-alarm fire.

Benford, a tall, bearded New Englander, is responsible for making sure that almost 5,000 simultaneous telephone calls reach their destinations around the clock.

“It’s always interesting. You never know who you’re going to get when you pick up the phone,” he said. Benford receives requests and trouble calls from all over the world.

He and his seven-member team keep watch over American Telephone & Telegraph’s Green Hill submarine cable station, one of two stations that transmit signals directly to Europe. The second is in Tuckerton, N.J.

West Coast Stations

In addition, AT&T; operates two West Coast stations, at Point Arena and San Luis Obispo, Calif., that transmit signals by three cables to Hawaii and on to Guam and Asia.

Other cables run from stations in Jacksonville Beach, Vero Beach, West Palm Beach, Miami and Key West in Florida to Puerto Rico, St. Thomas, Jamaica and Cuba. And one cable from Tuckerton goes to Bermuda and on to the Caribbean and South America.

The cables are jointly owned and operated by AT&T; and the destination countries, where bunkers almost identical to the Green Hill station are run by technicians from those countries.

Submarine cables provide inexpensive intercontinental communications. Despite the development of high-technology satellites, Benford said, old-fashioned undersea cables are still the fastest, most reliable and, in many cases, the only way to communicate across oceans.

“This is probably the most reliable thing I have ever worked with during the 20 years I have worked for this company,” said Wilfred Kashima, a supervisor at the San Luis Obispo station, situated half way between Los Angeles and San Francisco.

“They are so expensive to repair (that) they are designed for that kind of reliability,” he said. “But it costs a lot of money to put in that kind of design effort.”

Kashima said that only one of his two cables has ever malfunctioned in the 10 years that he has worked at the station.

The Atlantic cables carry about 65% of the telephone conversations to Europe. The other 35% are relayed by satellite.

Laser-Light Cables

When the first undersea cable to use laser light instead of electric signals is laid from New Jersey to Europe in 1988, undersea cables are expected to take another giant step ahead of satellite communications. The number of simultaneous telephone conversations possible on each cable will increase to 37,500.

One advantage cables have over 22,300-mile-high satellites is that satellites cause a three-second delay in communications.

For telephone callers, the delay is annoying--for computer-to-computer communication, it is often intolerable. The computers must be specially programmed to wait for a response.

The average caller has no choice between cable or satellite: It depends on the luck of the draw. But computer customers can often request cable.

The underground Green Hill bunker is built of heavily reinforced concrete 24 inches thick and topped by four feet of earth. It was built underground to protect it from natural and most man-made disasters.

The bunker has sensors that can detect nuclear radiation and cause steel air vents to automatically snap shut. After a few minutes, the vents open and filtering equipment prevents fallout from contaminating the center.

The station is capable of running for three weeks without contact with the surface.

The summer sun worshipers who carpet the beach a few hundred yards from the bunker are unaware that 20 feet below them runs an essential link between the United States and Europe.

Green Hill’s two undersea cables run up the beach and enter the underground bunker through a concrete wall facing the ocean. They thread their way overhead, then descend straight down into two refrigerator-size boxes. The station’s electronic system filters the signals into individual conversations. The deciphered calls are sent to their destinations across North and South America.

The two undersea cables are of different thicknesses. The thinner and older one is about two inches thick. The other is about twice that diameter.

The thicker cable, called TAT-6 because it was the sixth transatlantic cable to be laid, carries 4,000 two-way telephone conversations. It stretches from Green Hill, R.I., to St. Hilaire-de-Riez, France. The other cable, called TAT-5, runs to San Fernando, Spain, and carries 840 calls.

One Cable Is Armored

The thicker cable is encircled by an outer sheath of pencil-thick steel cables. The armor is often not enough to keep it from snapping when snagged by a fishing trawler’s nets. The thinner of the two cables is not armored.

When a cable breaks, a cable-laying ship is dispatched to repair the damage. The ship drops a grappling hook to the ocean floor, pulls the cable to the surface, resplices it and then drops it to the floor again. The cable does not break often and, when it does, it usually breaks in shallow water, where it is easier to repair.

The cables follow topography of the sea bottoms--up undersea mountain ranges higher than any on land and down into ocean canyons where the pressure per square inch reaches thousands of tons.

Near shore, the cables are laid using a plow that digs a two-foot-deep trough. The cable is dropped into the trough and covered.

Telephone conversations are transmitted across copper undersea cables in much the same way that radio signals are sent through the air.

Amplifiers that boost the electronic signals are attached to the cable every few miles. The amplifiers are powered by current that runs through the cable along with the telephone signals.

The Green Hill station cannot send enough current through the cable to power the entire thing, so an opposite current is sent from the other end. The two currents meet in the middle of the ocean and are equivalent to twice as much power flowing from one end.