The ancient Greeks used mirrors to transmit information, in a rudimentary way, using sunlight. In 1792, FABIO") designed a system of optical telegraphy, which, through the use of a code, towers and mirrors distributed along the 200 km that separate Lille from Paris, managed to transmit a message in just 16 minutes.
Although in 1820 the equations governing the capture of light within a smooth glass plate were known, it would not be until 90 years later (1910) when these equations were applied to the so-called glass cables thanks to the work of the physicists Demetrius Hondros") and Peter Debye in 1910.[11].
The confinement of light by refraction, the principle that makes fiber optics possible, was demonstrated by Jean-Daniel Colladon and Jacques Babinet in Paris in the early 1840s. The English physicist John Tyndall discovered that light could travel within water, bending by internal reflection, and in 1870 he presented his studies to members of the Royal Society of London.[12] A series of studies were carried out from this principle, in which demonstrated the potential of glass as an effective means of long-distance transmission. In addition, a series of applications based on this principle were developed to illuminate water streams in public fountains. Later, British engineer John Logie Baird filed patents describing the use of solid glass rods in light transmission for use in his electromechanical color television system. However, the techniques and materials used did not allow light transmission with good performance. Optical signal losses were large and there were no optical coupling devices.
Only in the 1950s did optical fibers begin to interest researchers, with many practical applications being developed. In 1952, physicist Narinder Singh Kapany, drawing on the studies of John Tyndall, carried out experiments that led to the invention of optical fiber.
One of the first uses of fiber optics was to employ a bundle of fibers for image transmission, which was used in the endoscope. Using fiber optics, a semi-flexible endoscope was achieved, which was patented by the University of Michigan in 1956. In this invention, new fibers were used covered with a material with a low refractive index, since they were previously impregnated with oils or waxes. Around this same time, hair-thin filaments that carried light over short distances came into use in both industry and medicine, so that light could reach otherwise inaccessible places. The only problem was that this light lost up to 99% of its intensity when passing through distances of up to 9 meters of fiber.
Charles K. Kao, in his 1956 doctoral thesis, estimated that the maximum losses that optical fiber should have, to be practical for communications links, were 20 decibels per kilometer.
In 1966, in a communication addressed to the British Association for the Advancement of Science, researchers Charles K. Kao and George Hockham"), from the laboratories of Standard Telephones and Cables, in England, stated that fibers of greater transparency could be available and proposed the use of glass and light fibers, instead of electricity and metallic conductors, in the transmission of telephone messages. Obtaining such fibers required great efforts from researchers, since the fibers up to They then presented losses of the order of 100 dB/km, in addition to a narrow passband and enormous mechanical fragility. This study formed the basis for reducing the losses of optical signals that until now were very significant and did not allow the use of this technology. In a theoretical article, they demonstrated that the large losses characteristic of existing fibers were due to minute intrinsic impurities of the crystal. 1 GHz pass-through for a length of 1 km, with the perspective of replacing coaxial cables. The use of 100 µm diameter fibers, wrapped in resistant nylon fibers, would allow the construction of threads so strong that they could not be broken by hands.
In 1970, researchers Robert Maurer, Donald Keck"), Peter Schultz, as well as Frank Zimar") working for Corning Glass, manufactured the first optical fiber by applying titanium impurities in silica, hundreds of meters long with the crystalline clarity that Kao and Hockman had proposed, although the losses were 17 dB/km.[13][14] During this decade, manufacturing techniques were improved, achieving losses of only 0.5 dB/km.
Shortly thereafter, physicists Morton B. Panish") and Izuo Hayashi") of Bell Laboratories demonstrated a semiconductor laser that could operate continuously at room temperature. In addition, John MacChesney and his collaborators, also at Bell Laboratories, independently developed fiber preparation methods. All of these activities marked a turning point as the means now existed to bring fiber optic communications outside the laboratories and into the realm of mainstream engineering. Over the next decade, as research continued, optical fibers steadily improved in transparency.
On April 22, 1977, General Telephone and Electronics sent the first telephone transmission over fiber optics, at 6 Mbit/s, in Long Beach, California.
A device that allowed the use of optical fiber in interurban connections, reducing its cost, was the optical amplifier invented by David N. Payne, of the University of Southampton, and by Emmanuel Desurvire at Bell Laboratories. They were both awarded the Benjamin Franklin Medal in 1988.
In 1980, the best fibers were so transparent that a signal could travel 150 miles of fiber before fading to undetectability. But optical fibers with this degree of transparency could not be manufactured using traditional methods. Another breakthrough came when researchers realized that pure silica glass, without any light-absorbing metal impurities, could only be made directly from vapor components, thus avoiding the contamination that inevitably resulted from the conventional use of foundry crucibles. The technology under development was based primarily on knowledge of chemical thermodynamics, a science perfected by three generations of chemists since its original adoption by Willard Gibbs in the 19th century.
Also in 1980, AT&T submitted to the United States Federal Communications Commission a project for a 978-kilometer system that would connect major cities along the route from Boston to Washington, D.C. Four years later, when the system began operating, its cable, less than 10 inches in diameter, provided 80,000 voice channels for simultaneous telephone conversations. By then, the total length of fiber cables in the United States alone reached 400,000 kilometers.
The first transoceanic fiber optic link was the TAT-8, which began operating in 1988, using glass so transparent that amplifiers to regenerate weak signals could be placed at distances of more than 64 kilometers. Three years later, another transatlantic cable doubled the capacity of the first. Since then, optical fiber has been used in a multitude of transoceanic links or between cities, and its use is gradually extending from the backbone networks of operators to end users.
Nowadays, due to its minimal signal losses and optimal bandwidth properties, in addition to its reduced weight and size, optical fiber can be used over longer distances than copper cable.