First Commercial Test of Fiber-Optic Telecommunications

The invention of fiber-optic technology revolutionized the telecommunications industry and advanced medical procedures. The first tests of the technology demonstrated successfully that it was possible for a single pair of fibers to carry nearly six hundred telephone conversations with a high degree of reliability and at a reasonable cost.

Summary of Event

Ever since Samuel F. B. Morse, inventor of the telegraph, sent his famous message “What hath God wrought?” by means of electrical impulses traveling at the speed of light over a 66-kilometer-long telegraph line strung between Washington, D.C., and Baltimore in 1844, scientists have worked to develop faster, less expensive, and more efficient means of conveying information over great distances. The impact of the telegraph, or “lightning wire,” as it came to be known, was immediate and far-reaching. It was used at first to report stock market prices and the results of political elections. Telegraphy Telegraphy played a large role in the American Civil War; in fact, the first transcontinental telegraph sent was a message from Stephen J. Field, chief justice of the California Supreme Court, to President Abraham Lincoln on October 24, 1861, declaring that state’s loyalty to the Union. By 1866, telegraph lines reached all across the continent, and a telegraph cable had been laid beneath the Atlantic Ocean, linking the Old World with the New World. Fiber-optic technology[Fiber optic technology]
Telecommunications;fiber optics
Telephone technology
[kw]First Commercial Test of Fiber-Optic Telecommunications (May 11, 1977)
[kw]Commercial Test of Fiber-Optic Telecommunications, First (May 11, 1977)
[kw]Test of Fiber-Optic Telecommunications, First Commercial (May 11, 1977)
[kw]Fiber-Optic Telecommunications, First Commercial Test of (May 11, 1977)
[kw]Telecommunications, First Commercial Test of Fiber-Optic (May 11, 1977)
Fiber-optic technology[Fiber optic technology]
Telecommunications;fiber optics
Telephone technology
[g]North America;May 11, 1977: First Commercial Test of Fiber-Optic Telecommunications[02830]
[g]United States;May 11, 1977: First Commercial Test of Fiber-Optic Telecommunications[02830]
[c]Science and technology;May 11, 1977: First Commercial Test of Fiber-Optic Telecommunications[02830]
[c]Inventions;May 11, 1977: First Commercial Test of Fiber-Optic Telecommunications[02830]
[c]Communications and media;May 11, 1977: First Commercial Test of Fiber-Optic Telecommunications[02830]
Morse, Samuel F. B.
Bell, Alexander Graham
Maiman, Theodore Harold
Kao, Charles K.
Kapany, Narinder S.

Another American inventor, a Scottish emigrant to the United States, made the leap from the telegraph to the telephone. Alexander Graham Bell, as a teacher of the deaf, was interested in the physiology and physics of speech. In 1875, he began experimenting with ways to transmit sound vibrations electrically. He realized that an electrical current could be modulated to resemble the vibrations of speech. Bell patented his invention on March 7, 1876; on July 9, 1877, he founded the Bell Telephone Company.

In 1880, five years after inventing the telephone, Bell invented a device called the “photophone” with which he demonstrated that speech could be transmitted on a beam of light. Light is a form of electromagnetic energy. It travels in a vibrating wave. By modulating the amplitude, or height, of the wave, a light beam can be made to carry messages. Bell’s invention employed a mirrored diaphragm that converted sound waves directly into a beam of light. At the receiving end, a selenium resistor connected to a headphone reconverted the light into sound. “I have heard a ray of sun laugh and cough and sing,” Bell wrote of his invention.

Although Bell demonstrated that he could transmit speech over distances of several hundred meters with the photophone, the device was cumbersome and unreliable and never caught on like the telephone. One hundred years would pass before large-scale commercial application of Bell’s dream of talking on a beam of light would become a reality.

Two key technological advances were needed first: development of the laser and development of high-purity glass. In 1960, Theodore Harold Maiman, a physicist and electrical engineer working at Hughes Research Laboratories in Malibu, California, built the first laser. Lasers
Physics;lasers The laser produces an intense, narrowly focused beam of light that can be modulated to carry huge amounts of information. It soon became apparent, however, that even bright laser light could be broken up and absorbed by smog, fog, rain, and snow. In 1966, Charles K. Kao, an electrical engineer working for the Standard Telecommunications Laboratories in England, proposed that glass fibers be used to transmit the message-bearing beams of laser light without disruption.

Optical glass fiber is made from common materials consisting basically of silica, soda, and lime. To make the optical fiber, the inside of a thin-walled silica glass tube is coated with successive layers of extremely thin glass. Typically, a tube is lined with a hundred or more such layers. The tube is then heated to 2,000 degrees Celsius and collapsed into a thin glass rod, called a preform. The preform is then pulled into thin strands of fiber. The fibers are coated with plastic to protect them from being scored or scratched, and then sheathed in flexible cable.

The first glass fibers produced contained many impurities and imperfections, which resulted in significant light losses. Signal repeaters were needed every few meters to boost the fading light pulses. In 1970, however, researchers at the Corning Glass Works, in New York, developed a fiber pure enough to carry light at least 1 kilometer without amplification.

The telephone industry quickly seized on the new fiber-optic technology. It was anticipated that a bundle of optical fibers having the diameter of a pencil could carry several hundred telephone calls at the same time. Optical fibers were first tested by telephone companies in big cities, where ever-increasing, high-density phone traffic often overloaded the capacity of underground conduits. On May 11, 1977, American Telephone and Telegraph American Telephone and Telegraph Company (AT&T), in a cooperative venture with Illinois Bell Telephone, Western Electric, and Bell Telephone Laboratories, began the first commercial test of fiber-optic telecommunications in downtown Chicago. In the keynote speech at the opening ceremonies for the Chicago system, AT&T’s vice president of engineering and network services, Morris Tanenbaum, noted that “there is a long, often torturous path that must be traveled between a research discovery and its application in a practical cost-effective system.” The experimental system in Chicago represented the culmination of nearly twenty years of research and development, much of it conducted at a furious and highly competitive pace.

The Chicago test was intended to evaluate the potential of fiber-optic telecommunications under actual operating conditions and to acquire experience in the installation, operation, and maintenance of such a system in a congested, urban area. The system consisted of a 2.4-kilometer cable laid beneath the city’s streets in existing telephone ducts. The cable, 1.3 centimeters in diameter, linked an office building in Chicago’s business district with two telephone exchange centers. Voice, data, and video signals were coded into pulses of laser light and transmitted through the hair-breadth glass fibers. The tests demonstrated successfully that it was possible for a single pair of fibers to carry nearly six hundred telephone conversations with a high degree of reliability and at a reasonable cost.

Six years later, in October, 1983, scientists at Bell Laboratories Bell Telephone Laboratories succeeded in transmitting the equivalent of six thousand telephone signals through an optical fiber cable 161 kilometers long. Since that time, countries all over the world, from England to Indonesia, have developed optical communications systems.


Hailed as a revolutionary new technology, the greatest impact of fiber optics has been in the telecommunications industry. Optical fibers provide greater information-carrying capacity—a single fiber can now carry thousands of conversations with complete freedom from electrical interference. Made of common materials—glass and plastic—they are less expensive than copper wire, weigh less, and take up considerably less space. Because the laser-light signals do not degrade over distances, they do not require the regular and periodic amplification that electrical signals passing through a copper wire require. In terms of both economics and logistics, fiber-optic technologies revolutionized the telecommunications industry, until satellite and wireless communications surpassed land-based systems.

One of the first uses of fiber optics and perhaps its best-known application is the fiberscope, a medical instrument that permits internal examination of the human body without surgery or X-ray techniques. The fiberscope, or endoscope, developed in the late 1950’s by Narinder S. Kapany (who coined the term “fiber optics”), a physicist and president of Optical Technology, Inc., consists of two fiber bundles. One of the fiber bundles transmits bright light into the patient, while the other conveys a color image back to the eye of the physician. The fiberscope has been used to look for ulcers, cancer, and polyps in the stomach, intestine, and esophagus of humans. Medical instruments, such as forceps, can be attached to the fiberscope, allowing the physician to perform a range of medical procedures, such as clearing a blocked windpipe or cutting precancerous polyps from the colon. Fiber-optic technology[Fiber optic technology]
Telecommunications;fiber optics
Telephone technology

Further Reading

  • Boraiko, Allen A. “Fiber Optics: Harnessing Light by a Thread.” National Geographic, October, 1979, 516-535. Fascinating and lively account of the development of fiber optics intended for the average reader. Provides a historical context for the breakthrough discoveries of the 1960’s and 1970’s in the areas of laser and glass fiber technologies. Based in part on interviews with scientists and researchers working in the field of fiber optics. Includes stunning color photographs.
  • Boyle, W. S. “Light-Wave Communications.” Scientific American 237 (August, 1977): 40-48. Describes the experimental fiber-optic system set up in Chicago in May of 1977, the first commercial test of “light-wave” telephone service. The article provides detailed, technical information on the laser technology involved as well as the operating principles of optical fiber transmission. Includes diagrams showing cross sections of lasers, optical fibers, and cables.
  • Bruce, Robert V. Bell: Alexander Graham Bell and the Conquest of Solitude. Ithaca, New York: Cornell University Press, 1990. Reprint of the 1973 edition. Considered by many to be the definitive biography of Bell. Bruce describes Bell’s invention within the context of the history of American science and technology. Heavily illustrated. Includes a bibliography and index.

  • Inventors and Discoverers: Changing Our World. Washington, D.C.: National Geographic Society, 1988. Beautifully illustrated and well-written tribute to inventors and their inventions. Contains fascinating details of the lives of the men and women who made discoveries that dramatically changed the world in which they lived. The essay by science writer Stephen Hall, “The Age of Electricity,” covers the contributions made by Morse and Bell. Includes an introductory essay by Daniel Boorstin, American historian and former Librarian of Congress.
  • Kapany, N. S. Fiber Optics: Principles and Applications. New York: Academic Press, 1967. Assumes an understanding of physics at the undergraduate level. The first part of the book provides a theoretical background, while the second part covers the applications of fiber optics in various fields, including medicine, photoelectronics, and high-speed photography.

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