City of Light: The Story of Fiber Optics

202 CITY OF LIGHT
elements. A call from Boston to Los Angeles hops across the continent from
point to point: through Hartford, New York, Philadelphia, Pittsburgh, Columbus,
Indianapolis, St. Louis, Kansas City, Cheyenne, Salt Lake City, and Las
Vegas. This modular structure makes the network easier to build, operate,
and maintain. If a town grows, a phone company can add cables from that
town to the nearest node on the national network. If a careless contractor
breaks a buried cable, the network switches signals around the break while
technicians fix the damage. Total investment in the network is tremendous,
but individual links are relatively inexpensive.
In contrast, submarine cables can span thousands of kilometers (or miles)
of ocean and cost hundreds of millions of dollars; the biggest today have cost
over a billion dollars. 2 Some run between two coastal landings, such as from
New Jersey to France; others land at several points on the coasts of different
countries. Virtually all the cable is submerged, and much lies in the deep sea,
far beyond the reach of technicians in four-wheel-drive trucks. Repairs mean
sending a cable ship to find the damage and haul the cable to the surface for
repairs.
Repairs take so much time and money that undersea cable operators demand
the utmost in reliability. Their specifications insist on no more than
two failures in the cable’s quarter-century lifetime that require hauling the
cable to the surface. To meet those demands, cables must withstand pressures
to 10,000 pounds per square inch, without corroding in salt water. Repeater
housings must protect electronics from the same tremendous pressures, without
letting a drop of water touch sensitive components.
The deep sea shields cable from most disturbances save massive underwater
landslides or earthquakes. However, fishing trawlers and ship anchors
threaten the ends in shallow water, which are armored with thick steel wires,
then buried in a protective trench cut into the ocean floor. Fishing is banned
from the zones around cable landings, and just to be sure, cable owners hire
patrol boats to warn away violators.
An Old Tradition of Bold Ventures
Submarine cables began carrying electrical telegraph signals in the midnineteenth
century. The first crossed the English Channel in 1850. It didn’t
work well because it was poorly insulated, and a fisherman soon cut it. But
the next year a better cable followed, bringing news to England as fast as to
the rest of Europe. American entrepreneur Cyrus Field soon decided to run a
cable from Newfoundland to England. Some eminent scientists thought the
idea was daft, but on the second attempt, Field laid a cable that in 1858
succeeded in relaying a handful of messages across the Atlantic before failing.
The Civil War delayed the first permanent cable link across the Atlantic until
1866. 3
A continuous cable running some 2000 miles (3200 kilometers) under the
sea was an impressive achievement for Victorian-era technology. One reason