to Videolink arrow

Newton logo to print

Telecommunications

 

Overview

Alexander Graham Bell invented a talking machine that used pulses of electricity to carry sound through copper wires and called it the telephone. Soon after, he tested the photophone, another talking machine that used a beam of sunlight to carry voices from one place to another. Although he had high hopes for the future of his photophone, it depended on a constant source of sunlight and proved to be impractical. Not until the invention of lasers and optical fibers did Bell's dream come true. In the mid-1970s, researchers began pumping pulses of laser light through thin glass fibers to move information. Light is actually a sequence of vibrations. Scientists discovered how to vary these patterns of vibrations and convey information. When a conversation occurs over a telephone system that uses optical fibers, the vibrations of your voice are converted to the pattern of the laser. At the other end, these variations are turned back into sound. Because lasers can be modulated with highly complex patterns much greater quantities of information can be transmitted. Stringing electrical cables or optical fiber cables from place to place is very expensive. Because the new optical fibers can handle so much more information than traditional telephone wires, it has become more economical to replace conventional wires with the new technology. And, fiber-optic communications are not limited to telephone conversations. They can even be used to transmit complex information, like television or data between computers. As fiber-optic cables interconnect our area, it will be possible to see and purchase items from distant stores, participate in classes or meetings happening across the world, see people you're talking to on the telephone and have instant access to the latest information stored in libraries, all without leaving your home! Other industries benefit from fiber optics. Physicians use them to examine areas of the body instead of performing surgery. In industry, fiber optics aid workers in repairing jet engines, nuclear reactors and other complicated machinery. In the future, fiber optics will be used to control lighting, heating, air conditioning, security systems and other types of machinery. The most interesting uses of fiber optics are yet dreamed about!

Activity

Light does travel in a straight line but there are times when it doesn't. Light can be inside a curving stream of water because the path of the light changes direction as it is reflected internally by the water. Discover how fiber optics use this principle. Materials:
  • Tall, clear and slim jar with a lid
  • Newspaper
  • Flashlight
  • Hammer
  • Large nail
  • Large container
1. Make two holes in the jar lid with the hammer and the nail. Make a large hole near one edge and a smaller hole near the opposite edge. 2. Fill the jar three quarters full with water. 3. Turn on the flashlight and hold it to the bottom of the jar so the light shines into the jar. 4. Wrap the jar and the flashlight together in the newspaper. Leave the lid of the jar uncovered. Be careful not to spill the water. If needed, place tape over the holes until the pieces are wrapped together. 5. Now get ready to "pour" light. Turn the lights off and tilt the jar so the water flows out the largest hole into a large container.

Resources

  • Billings, Charlene W. Fiber Optics: Bright New Way to Communicate. New York: Dodd Mead & Company, 1986.
  • Burkig, Valerie. Photonics, The New Science of Light. Hillside. New Jersey: Enslow Publications, 1986
  • Whyman, Kathryn. Light and Lasers. New York: Glouchester Press, 1986.