including a TAT-9 list of facts, TAT-9 technology discussion
and a description on the making of glass fiber for
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FOR RELEASE MONDAY, MARCH 2, 1992
NEW YORK, N.Y. -- AT&T today activated service on a new $450-million undersea fiber optic cable system linking the United States and Canada with the United Kingdom, France and Spain.
The new system will be able to handle the equivalent of 80,000 simultaneous phone calls or any combination of voice, data and video signals--double the capacity of previous-generation submarine fiber optic cables.
As service begins on the new TAT-9 system--the ninth consortium-owned cable across the Atlantic Ocean--AT&T has already begun installing the next transatlantic fiber optic system, TAT-10.
"Usually three or four years pass between the construction of transoceanic systems," said Al Stark, senior vice president- AT&T's international operations division. "But demand for fiber optic services has skyrocketed to the point we're now turning up service on one cable and already installing the next."
To meet the tremendous demand for undersea fiber optic systems, AT&T today operates a global fleet of five cable ships and a cadre of marine tools that include four sea plows, a seabed tractor and three SCARAB remotely operated vehicles used for cable burial and repair operations.
The 9,310-kilometer (5,586-mile) TAT-9 system will be the first direct transatlantic fiber optic link to Spain, which has been served since 1970 by TAT-5, an analog cable capable of handling only 845 simultaneous phone calls. The TAT-9 system was designed by AT&T Bell Laboratories, STC of Great Britain, Submarcom of France and MPBT of Canada.
"This fiber optic route to Spain will allow us to directly link up with undersea fiber optic systems that reach Italy, Greece, Turkey and Israel," Stark said. "As a result, most calls between North America and both the Mediterranean and Mideast regions will be noticeably clearer."
The new TAT-9 route also will give business customers on both sides of the Atlantic fiber optic route diversity and faster service restoration, Stark added.
"Normally, providing backup service for undersea cables takes several hours to implement on satellite," he said. "But with TAT-9, customers could get backup restoration in about half that time and with a significantly improved quality of service. This is particularly important for customers who transmit large amounts of data from one continent to the other."
Resorts Condominiums International is AT&T's first International ACCUNET(R) Digital Services (IADS) customer to be placed on the new TAT-9 fiber optic system.
According to Larry Darrah, director of systems services for RCI, "We chose a 56-kilobit dedicated circuit on TAT-9 to support increased demand for real-time data traffic from our European operations and to provide route diversity between our key data centers in the U.S. and the U.K."
TAT-10, slated for service this fall, will directly link the United States with Germany and the Netherlands via submarine cable for the first time. This will provide much-needed communications capacity for the unification of Western European markets beginning this year as well as the emerging market economies of Eastern and Central Europe.
Stark said the technology advances inherent in the ninth and tenth transatlantic systems are also significant, particularly when compared with transoceanic communications cables more than 30 years ago.
The first transatlantic cable, for instance, was actually two cables laid side-by-side--one for calls going east, the other for those heading west. The total capacity of TAT-1 was about 51 phone calls.
"At that time, the world's record for running a mile was four minutes," he said. "If a runner could improve his time as much as undersea cable transmission capacity has, he could run a mile today in less than a fifth of a second."
Both TAT-9 and TAT-10 operate at 565 megabits (million bits) per second over each of two optical-fiber pairs. High- speed pulses of light generated by lasers carry voice, data and video information through the glass fibers. A third fiber pair is included for backup.
In addition to operating twice as fast as the lasers in TAT-8, the TAT-9 and TAT-10 lasers will work at a wavelength of 1.5 microns. This results in less loss of light intensity than in earlier submarine systems, when lasers operated at 1.3 microns.
This difference allows increased spacing between repeaters, the lightwave-signal regenerators that are placed at intervals along the cable to maintain signal strength and clarity.
Stark said AT&T and the 38 other owners of the TAT-9 route also were able to create a cost-effective cable system by linking five countries together for the first time.
"In previous transoceanic systems, we've used underwater branching units to link as many as three countries together-- with calls transmitted basically east and west," Stark said.
"We would have had to build two or three separate undersea cable systems to link five countries, if we couldn't switch call routes somewhere out in the ocean. However, our TAT-9 team has developed unique underwater branching multiplexers which can do just that."
AT&T is the largest investor in TAT-9, with approximately one-fourth of the system's circuits. The other major co-owners include British Telecom, Teleglobe Canada, France Telecom and Telefonica of Spain.
AT&T also is currently working on construction of TPC-4, a major transPacific route linking the United States with Canada and Japan. Like its sister TAT-9 and TAT-10 Atlantic systems, TPC-4--slated for service this fall--also will be capable of handling up to 80,000 simultaneous phone calls.
Goonhilly, U.K.; St. Hilaire, France; Conil, Spain
Spain, Italy, Greece, Turkey, Israel and other Mediterranean and Middle Eastern nations. CONSTRUCTION COST: $450 million MAJOR INVESTORS: AT&T, British Telecom, Teleglobe Canada, France
Telecom, Telefonica of Spain, (39 investors in total). TAT-9 TECHNOLOGY
TAT-9, the newest undersea lightwave transatlantic telecommunications cable system, is the first transoceanic cable system with underwater branching multiplexers, which allow direct connections among five points on both sides of the Atlantic.
The landing points are in the U.S., Canada, the United Kingdom, France and--the first time for a lightwave system-- Spain. The Spanish connection completes a trans-Mediterranean fiber-optic cable link with Italy, Greece, Turkey and Israel.
TAT-9 operates at 565 megabits (million bits) per second over each of two optical-fiber pairs. High-speed pulses of light generated by lasers carry voice, data and video information through the glass fibers. A third fiber pair is included for back-up. The system was designed by AT&T Bell Laboratories, with STC of Great Britain, Submarcon of France, and MPBT of Canada.
The system can handle 80,000 simultaneous two-way voice telephone calls or any combination of voice, data, and video signals--twice the capacity of TAT-8, the world's first undersea lightwave system, which was installed just four years ago.
In addition to operating twice as fast as the lasers in TAT- 8, the TAT-9 lasers work at a wavelength of 1.5 microns. This results in less loss of light intensity than in earlier submarine systems with lasers working at 1.3 microns and allows for an increase in spacing between repeaters, lightwave-signal regenerators that are placed at intervals along the cable to maintain signal strength and clarity.
As light pulses travel through optical fiber, they tend to broaden and lose their shape. Since they convey information as binary signals, with their presence or absence representing a one or a zero, spacing between pulses is important.
In each regenerator, incoming optical signals are detected and changed to electrical digital signals, then passed through high-frequency silicon bipolar integrated circuits for amplification and regeneration.
This electrical pulse stream of 560 megabits per second is then fed to a laser transmitter and reconverted to infrared light pulses, which are then launched into a 60-mile-long fiber terminated by the next regenerator.
TAT-9 incorporates 51 repeaters; TAT-8 uses 109. TAT-7, which uses electrical analog signals over copper cable rather than light pulses over optical fiber, has 662 repeaters. AT&T manufactured the repeaters and assembled the branching multiplexers using subsystems supplied by AT&T and MPBT.
The underwater branching multiplexers, located at three points beneath the ocean, allow reconfiguration of telecommunications traffic so that calls can be reallocated from one leg of the system to another if necessary in response to service demands.
Multiplexing is the interleaving of digital signals from various conversations or data streams onto a single fiber pair, with bits from one conversation, for example, fitted into the spaces of another.
TAT-9 transmits multiplexed information from each of the five countries to one of the branching units, which multiplexes the combined signals and transmits them across the ocean floor.
Eastbound calls (originating in the U.S. and Canada) are carried to a branching unit, multiplexed onto the major portion of the cable, transmitted across the ocean to a second unit, and then transmitted either to Spain or to the third unit and then to the United Kingdom or France.
West-to-east transmissions beginning in Spain travel to a branching multiplexer and cross the ocean to the westernmost branching unit before being sent either to the U.S. or Canada.
Those from the United Kingdom and France are combined at TAT-9's easternmost branching multiplexer and carried to the one near Spain and onto the main cable to cross the Atlantic to the western branching unit to be transmitted either to the U.S. or to Canada.
The diameter of most of the TAT-9 fiber-optic cable is 3/4," with shore ends heavily armored and buried and with unburied cable steel-clad to a depth of 8,500 feet to protect against fish bites.
TAT-9's western landing points are Manahawkin, N.J., and Pennant Point, Canada. Some 3,000 miles east, TAT-9 comes ashore at Conil, Spain; St. Hilaire, France; and Goonhilly, England.
More than 30,000 miles of hair-thin optical fiber were needed to make the TAT-9 undersea cable.
The fiber was manufactured at the AT&T Atlanta Works, the world's largest manufacturing facility for communications cable and wire products. Located in Norcross, Georgia (17 miles northeast of Atlanta), the plant has the equivalent of 29 football fields in manufacturing space.
The special glass fiber used in TAT-9 was developed by AT&T Bell Laboratories. It is designed to channel high-speed (560- million-bit-per-second) light pulses at a wavelength of 1.5 micrometers. The light travels more than 60 miles between repeaters that refresh the transmission signal as it crosses the floor of the Atlantic Ocean.
Although the total diameter of the fiber is 245 micrometers (about the thickness of an average human hair), the solid cylindrical core that carries the light pulses is only 8.3 micrometers (three ten-thousandths of an inch) in diameter and is surrounded by a concentric series of layers called cladding.
The core has a higher refractive index than the cladding as a result of controlled chemical composition. This assures efficient guiding of the light pulses.
Making the fiber for a lightwave cable is a two-step process. First, ultra-pure materials are combined to form a solid glass cylinder called a preform, using a process invented by Bell Labs called modified chemical vapor deposition (MCVD).
Then the preform is mounted in a vertical position at the top of a fiber-drawing furnace and heated to the softening point. The white-hot tip of the preform is pulled downward, drawing the glass into a six-mile-long strand, which is coated with a special plastic during its descent to a takeup spool.
The underwater fiber is exposed to a tensile test of 200,000 pounds per square inch as it transfers to the spool. The plastic coating and high stress-testing level are necessary to ensure the reliability of underwater fiber.
The drawn lengths of fiber are spliced together to form the 60-mile-long repeater-span lengths of fiber. The fiber sets are shipped to the Simplex Wire and Cable Company, in Portsmouth, New Hampshire, where the fiber is integrated with repeaters and undersea branching multiplexers assembled at AT&T's manufacturing facility in Clark, New Jersey, and the completed cable is loaded onto an AT&T cable ship.