Hopes High for Shark-Proof Optic Fiber Cable
MADRID, Spain (AP) _ Nobody gave a thought to sharks in October 1985 when AT&T and the Spanish telephone company Telefonica laid the world’s first non-experimental undersea optical fiber cable in the Canary Islands.
Much to the companies’ dismay, the cable attracted as much interest from hungry sharks as it did from the scientific community.
For reasons still not fully understood, sharks attacked the cable with a fury, biting through its power conductor and leaving at least 50 teeth embedded in its polyethylene coating.
But the war against the sharks was not fought in vain.
Although it was troubling at the time, the Canary Islands experience taught American Telephone & Telegraph Co. how to guard against shark attacks on much longer fiber optical cables that will cross the Atlantic, Pacific and Mediterranean.
″It was a blessing in disguise,″ said James M. Barrett, deputy director of international engineering for AT&T in Morristown, N.J., the executive responsible for all of AT&T’s submarine cables.
From now on, the vulnerable portions of all undersea fiber optical cables laid by AT&T will be wrapped in two layers of steel tape that resist even the jaws of monster sharks.
As a public service, AT&T shared its findings with other companies in Europe and Japan laying submarine cables.
Telephone conversations and video signals travel through optical fiber cables as pulses of laser light.
Optical fibers dramatically increase the amount of data that can be transmitted on a cable. The technology also does away with the distortion frequent in satellite and conventional copper cable transmissions.
The optical fiber cable is to include communications channels that will increase ten-fold the number of telephone conversations and other data transmissions possible at any given time through the cable.
Undersea coaxial cables currently in use carry between 1,000 and 2,000 simultaneous telephone conversations. A 280-megabit optical fiber cable can carry 8,000 conversations. With a circuit multiplier, that number can be increased to 40,000.
Sharks began attacking and chomping on Optican 1 shortly after AT&T laid about 76 miles of cable between Tenerife and Gran Canary, two islands in the chain that lie off the northwest coast of Africa.
AT&T engineers at first believed the sharks were attracted to the electromagnetic field generated by the power supply for the lasers that amplify the signal carried by the cable.
In an experiment at a Mystic, Conn., aquarium, five hungry sharks ignored a cable when no electric current passed through. They daintily ate meat wrapped with a currentless cable without scratching its surface with their teeth.
They attacked the same meat and cable with a vengeance when electric current was passing through and sunk their teeth into a bare electrified cable, according to AT&T spokesman James Rogalski.
But Barrett said that there were other times when the sharks ignored the electrified cable. Speculation about the strange attraction now centers on some combination of electricity and vibration of taut cables.
Shark bites notwithstanding, on July 24 Telefonica managed to carry out simultaneous transmissions of five video signals and corresponding sound tracks on the Optican cable.
The shark-proof replacement, also to be called Optican 1, will be laid in late September.
AT&T only has to sheathe the portions of the cable that are not buried but are in the shallower water that sharks inhabit - less than a mile or two deep, depending on how cold the water is.
Laying of the first of two trans-Atlantic cables, called TAT-8, has begun from New Jersey and is scheduled to reach a point off Europe in the fall. From there it will divide into Great Britain and France, which are partners in the cable. The expected service date is June 30, 1988.
In 1991 AT&T and its partners plan to lay TAT-9, which will snake up the East Coast of the United States and Canada, then under the Atlantic to split off in sections to Britain, France and and the Canaries through to Spain.
In the Pacific, AT&T and 21 partners are planning to lay a cable from California to Japan and Guam via Hawaii that will go into service in December 1988.
In the Mediterranean, AT&T is bidding to lay MAT-2, which is scheduled to connect with a branch to the east and bring shark-proof optical fiber communications to Italy, Greece, Turkey and Israel before the end of the century.
Through a series of agreements with AT&T, Telefonica has been using Optican since June 1986 to test experimental telephone traffic between the two islands. Telefonica is trying to upgrade Spain’s entire telecommunicatio ns system in time for the 1992 Summer Olympics in Barcelona and World’s Fair in Seville.
End Adv Aug. 29-30