United States. Tele¬phones throughout the 28,000-acre park are linked by fiber optic trunk lines. Video transmissions by glass fibers are made to many individual hotel rooms on the property from one location. Lighting and alarm systems also use optical fibers.
In EPCOT Center (Experimental Prototype Com¬munity of Tomorrow), there are information booths equipped with television-tike, two-way video screens and speakers. The screens and speakers are connected by optical fibers to a central office. A visitor can activate the screen by touching it and select the information needed. Or the guest can talk to an operator who appears on the screen if requested.
American Telephone and Telegraph has in service a fiber optic trunk line that connects Boston, New York City, Washington, D.C., and Richmond, Virginia. The trunk line is part of a project 780 miles long. The light cable used is only about the thickness of a garden hose. Nevertheless, it can carry eighty thousand calls at once.
By July 1988, American Telephone and Telegraph will have laid a fiber optic cable beneath the ocean between North America and Europe. The cable is called TAT-8 because it is AT&T's eighth /transatlantic tele¬phone cable. TAT-1, a copper cable, was completed in 1956 and could carry fifty-one calls at a rime. TAT-7, the last copper cable, was laid in 1983. It can handle about eight thousand calls at once. ÒËÒ-8 will transmit forty thousand calls at one time. Even with TAT-8, a second fiber optic transatlantic cable, TAT-9, probably will be needed by 1991. Another undersea cable, between California and Hawaii, is planned.
The Japanese telephone company, Nippon Telephone and Telegraph, has placed glass fiber cables from one end of the country to the other. By 1990, similar lines will join Japan to Hong Kong, Australia, and New Zealand.
A fiber optic system in Munich and other cities of West Germany is called Bigfon. It transmits a video picture along with voice. In addition, Bigfon sends and receives copies of documents and other important papers.
Over fifteen hundred customers in Biarritz, France, use videophones and television channels made possible by fiber optics.
In the remote countryside of Manitoba, Canada, two towns are part of an experiment. Elie and St. Eustache have become "glass-wired" communities. Optical fibers connect keyboards and television sets in homes in these towns to distant computers. People who live there use the keyboards to get television shows, radio broadcasts, weather forecasts, news, farm and stock market reports. In addition, over three hundred items for sale at a large, well-known department store, Hudson Bay Company, can be viewed on television. To make a purchase, a customer types an item code, number of items wanted, size, color, and credit card number on the keyboard. Hudson Bay Company receives the order and ships the goods directly to the customer.
Near Tokyo, in Japan, there is an optical fiber com¬munications network known as HI-OVIS (Highly Interactive Optical Visual Information System). With this two-way system people can take an active part in edu¬cational classes such as piano lessons. They also can learn about schedules for airlines, trains, and concerts, and get up-to-the-minute news and weather reports.
New installations for communications at Kennedy Space Center in Florida use fiber optics. These include the Space Shuttle control center and operations building for Launch Complex 39. In addition, the Space Center's fiber optic system is used to check out experiments, such as those on board Skylab, before launch. Eventually, all of the facilities for the Shuttle at Kennedy Space Center will use fiber optic systems.
There arc many other uses for fiber optics. A medical instrument known as an endoscope is made from bundles of optical fibers packed inside a long, slim, bendable tube. A doctor slips this medical "spyglass" into a patient's throat, stomach, lungs, or intestines to look for anything abnormal. One bundle of fibers carries light to the tip of the probe. Another bundle of fibers transmits pictures back to an eyepiece. This allows a doctor to see inside the human body without surgery. And sometimes it locates early stages of serious diseases, such as cancers, that X-rays may miss. Miniature tools within a separate channel in the endoscope tube can remove samples of tissue for a closer look.
Veterinarians examine horses, cats, clogs, and other animals with similar fiber optic scopes. Pets sometimes choke on foreign objects. With the probe of the scope, the animal doctor can locate the object, snare it, and quickly remove it.
People peer into dangerous or hard-to-see places with industrial fiber optic scopes too. Workers can look inside and check radioactive reactors in nuclear power plants, the jet engines of airplanes, turbines, boilers, pipelines, gear boxes, and many other types of machinery.
Image conduits are large pipelines for light. They are formed from thousands of optical fibers that have been bundled and fused together into one unit. They can directly transmit images or pictures from one place to another. If the conduit is tapered on one end, it can be used to make an image larger or smaller. And if the fibers in the conduit are twisted, the picture can be turned upside down.
Wafer-thin plates sliced from fused bundles of optical fibers are used to make night-vision goggles or scopes. The plates are treated with chemicals that enable them to magnify moonlight, starlight, or any other available light thousands of times. With the goggles, U.S. Forest Service helicopter crews can spot even small embers on the ground that could start a fire.
Individual optical fibers guide light from one source to many switches and displays on the dashboard of a late model automobile or the instrument panel of a recently built jet fighter. The fibers are small and lightweight. And they are not bothered by other electrical equipment fitted closely behind the dash or panel. In some cars, optical fibers monitor parts of the car. They signal the driver if a light burns out or if a door is ajar.
Many kinds of sensors are made with optical fibers. These devices can detect changes in temperature, pres¬sure, or the presence or absence of something. Different sensors can check for a wide range of things at factories—from missing caps on soda bottles to toxic fumes. They help guide robots or other automatic machinery to manufacture items as intricate as electronic circuits or as large as automobiles.
Glass fibers are ideal for military defense. In addition to their other advantages, the fibers are easy to hide from an enemy. Metal detectors cannot locate them, for example. Also, the fibers are almost impossible to secretly tap or jam. Thus, vital messages are more likely to get through. Light-carrying fibers usually are not affected by radiation. And they can be used safely near ammu¬nition storage areas or fuel tanks because they do not create sparks as electricity can in copper wires.
The North American Air Defense Command is located deep inside Cheyenne Mountain in Colorado. Its com¬puters, linked by optical fibers, process radar information from around the globe. Army field communications systems also depend on optical fibers.
Optical fibers are being used by the University of Pittsburgh to connect school computers. A college stu¬dent or teacher will be able to get information from any connected computer, library, or classroom on campus. Other schools are installing similar networks.
The new technology of fiber optics has grown quickly in the past decade. In the next ten to fifteen years, the copper wire telephone trunk lines in most of the world will be replaced with glass "wires." These slender strands will harness pulses of light to transmit the human voice and vast amounts of information in a twinkling. More and more, people will use beams of light to communicate with each other.
Imagine how excited Alexander Graham Bell would be to know that his dream has come true.
3
How Are Optical Fibers Made?
The glass used to make optical fibers must be very pure. Light must be able to pass through the length of the fiber without being scattered, or losing brightness.
Though the glass in an eyeglass lens looks perfect, a three-foot-thick piece of this kind of glass would stop a beam of ordinary light. Tiny particles of iron, chromium, copper, and cobalt absorb or scatter the light.
The glass in an optical fiber is nearly free of impurities and so flawless that light travels through it for many miles. If ocean water were as pure, we would be able to see the bottom of the Mariana Trench, over thirty-two thousand feet down, from the surface of the Pacific.
An optical fiber has a glass inner core. Light travels through this highly transparent part of the fiber.
The core of an optical fiber is surrounded by an outer covering called the cladding. The cladding is made of a different type of glass from the core of the fiber. For this reason, the cladding acts like a mirror. Light traveling through the core of the fiber is reflected back into the core by the cladding—much like a ball bouncing off the inside wall of a long pipe. In this way, light entering one end of an optical fiber is trapped inside the core until it comes to the other end.
How do people make these gossamer threads of glass that can carry light around curves and corners and over long distances?
Optical fibers are manufactured in "clean rooms." The air in these rooms is filtered to keep out the tiniest particles of dust. Even the smallest