At the beginning of the 20th century, communications relied on mail, the telegraph, and the telephone. News did not travel quickly. Telephones were commonly shared through a party line system of several families. Waiting for your turn could be frustrating or inconvenient. Long distance and overseas calls were placed through telephone operators and could take hours to connect as they waited for available lines. Though telegrams could be transmitted rather quickly, someone at the other end still had to deliver them. People in remote areas could wait for several days before they received an "urgent" message.
At the close of the century, people can't imagine such slow, plodding ways to communicate. Can anyone imagine a teenager waiting for his or her turn on a party line? Unthinkable, because in today's world, tiny semiconductor lasers routinely transmit light pulses carrying billions of bits of information per second over glass fibers. This process has dramatically changed the telecommunications industry by making worldwide connection, by phone, fax, or the Internet, almost instantaneous. People routinely talk to or e-mail friends around the world, without thinking too much about the distance. Corporations and small businesses are truly global, because the technology is affordable.
The technical means for this communications revolution are lasers and fiber optics - a unique blending of light and glass that transmits our words and thoughts, orders and memos, data and video anywhere in the world, immediately. A single optical fiber combined with fiber amplifiers can carry tens of millions of phone conversations, tens of thousands of television channels or transmit an entire encyclopedia in one-thousandth of a second. By the end of 1998, there were more than 215 million kilometers of optical fiber installed for communications worldwide. The optical fibers transmit light pulses up to 13,000 miles, and are handling data rates that are doubling each year. Today, optical fibers are the best conduit for delivering an array of interactive services, using combinations of voice, data, and video.
A few key people are responsible for this revolution, as are thousands of engineers who designed and developed the manufacturing and delivery systems to make it happen. In the 1940s and early 1950s Charles Townes and Arthur Schawlow were deeply interested in the field of microwave spectroscopy, a field that was delving into the characteristics of molecules. Neither had planned to invent the laser - what they wanted was to develop a device to help them study molecular structures.
They were eager to use microwave radiation of short wavelengths, because as the wavelengths became shorter, the interaction with molecules became stronger. The technical challenge was to build a device small enough to generate the required small wavelengths - something that was beyond current manufacturing techniques. Townes had the idea to use molecules instead of a device to generate the desired frequencies. Initially, there seemed no practical way of doing this, but in a moment of sudden inspiration he realized how to use stimulated emission from molecules and atoms to amplify waves, which led to his invention of the maser (microwave amplification by stimulated emission of radiation).
The question remained whether stimulated emission could be used for wavelengths much shorter than those of microwaves - perhaps into the infrared region. Theoretical calculations by Townes, and a chance meeting with Schawlow, provided the answer. Schawlow's idea was to arrange a pair of mirrors, one at each end of a region of excited atoms or molecules, to bounce the light straight back and forth. This could produce a pure frequency and a highly directed beam by eliminating any beams bouncing in other directions. In the fall of 1957 they began working out the principles of a device that could provide these shorter wavelengths.
The paper they published in 1958, which laid out the principles for the laser (light amplification of stimulated emission radiation), caused an explosion of research by engineers and scientists at laboratories and universities around the world. Townes and Schawlow had just launched a new scientific field, quite unintentionally. In 1960 they received a patent for their work and both were subsequently granted Nobel Prizes.
In May 1960, American physicist Theodore Maiman built the first laser to successfully produce a pulse of coherent light, using synthetic ruby as the laser medium. The first continuously operating laser was achieved a few months later. A July 1960 issue of Electronics magazine made a mild statement about the new device: "Usable communications channels in the electromagnetic spectrum may be extended by development of an experimental optical-frequency amplifier."
Communications engineers were ecstatic. The information revolution was already upon them, and they knew that the traditional technologies of electric signals and radio waves would not be enough to handle future communications traffic. They had already begun to look for ways to increase bandwidth (information carrying capacity). Telephone companies thought video telephones were imminent and would further escalate bandwidth demands. Laser technology gave them hope. Now all someone had to do was invent a means to channel the powerful optical waves effectively.
Some early work on glass-clad fibers attracted attention, but most technical opinions deemed glass-clad fibers excellent for medical imaging, but much not very practical for communications over long distances. Fortunately a small team at Standard Telecommunications Laboratories in the United Kingdom did not dismiss the potential of glass. One of its engineers, Charles K. Kao, collected samples from fiber makers and carefully researched the properties of bulk glasses. He believed that the high losses of early fibers were due to impurities and not to the silica glass itself. His research and belief that fiber loss could be reduced significantly attracted the interest of the British Post Office, which also operated the British telephone network, and soon a sizeable research fund was tapped to study the problem.
Based on Kao's work, laboratories around the world also began dealing with the problem. A breakthrough at Corning was one of the most important in the development of this technology. In 1970 Robert Maurer demonstrated the first low-loss fiber. By 1974 John MacChesney at Bell Labs introduced an alternative synthesis process leading to low contamination and precise index of refraction profiles.
In 1975, engineers at Laser Diode Labs developed the first commercial continuous-wave semiconductor laser operating at room temperature. Smaller than a grain of sand, this opened the door to the use of lasers to transmit optically encoded telephone conversations over fiber-optic cables. Another major step occurred in 1987 with the introduction of erbium-doped fiber amplifiers, which provide multiple channels of laser light and can handle 80 million telephone calls simultaneously.
In 1988 the first transoceanic fiber cable, TAT-8, was laid. Economically, this made a tremendous difference, first to industry, and ultimately to consumers. In comparison, the first trans-Atlantic copper cable cost $1 million per circuit to install in 1956; TAT-8 cost less than $10,000 per circuit.
Aside from providing the basis for modern communications system, the laser is a versatile tool used in many industries. It is used in manufacturing to cut precision parts, in medical applications such as eye surgery, in satellites to transmit weather and climate information, in scanners to read bar codes at cash registers, and in devices to play music on compact discs.
