History of Fiber Optic Communications - a tribute to the great Inventors

It is good to start with ‘Once upon a time there lived Mr. Claude Chappe in France who invented the Optical semaphore telegraph. That was in 1790s. The history of Optical communication systems dates back to that period. Alexander Graham Bell developed the first optical telephone system in 1880. He named his new device suitably as Photophone.

Alexander Graham Bell became part of the history by inventing the telephone, which is his masterpiece invention. Alexander Graham Bell’s Photophone invention stayed as an experimental invention but could not realized. It took another 40 years till and England scientist Mr. John Logie Baird and US scientist Mr. Clarence W. Hansell brought up the idea of using arrays of hollow pipes or transparent rods to transmit images for television or facsimile systems in 1920s.

Abraham Van Heel from Netherlands and Harold H. Hopkins from Britain in 1945 separately wrote about imaging bundles. Both reported about the fibers, but with slightly different ideas. When Hopkins reported on imaging bundles of unclad fibers, Van Heel reported on simple bundles of clad fibers. Van Heel detailed about a bare fiber having transparent cladding with a lower refractive index. He said that this clad will protect the fiber reflection surface from outside distortion and greatly reduce interference between fibers, when put into operation together. Van Heel’s idea of a clad over the core of the fiber was more practical as we can see today’s optical fibers are manufactured with a doped silica core with a silica cladding.

Abraham Van Heel thus became the prominent contributor towards the new age optical fiber telecommunication.. Along with Brian O'Brien, Van Heel progressed towards the innovation of cladding fiber optic cables. Before Van Heel optical fibers developed were bare and lacked any form of cladding. If there is no cladding layer over the core of the fiber the total internal reflection occurs at the glass - air interface. Abraham Van Heel could correctly point to a bare fiber or glass or plastic with a transparent cladding of lower refractive index. This development of cladding of lower refractive index made the total internal reflection to happen inside the core path.

Glass cladded fibers having an attenuation of around 1 decibel (dB) per meter were developed by 1960. These fibers were used in medical imaging to observe the internal body parts etc., The attenuation of 1 decibel or dB is too high for communication purpose.

The credit of inventing the single mode fiber goes to Elias Snitzer of American Optical who could put forward the theory of a fiber with a small core. This core is too small that it could carry light with only one waveguide mode. This restriction of waveguide by limiting the core size of fiber was very crucial in the development of modern day telecommunication grade optical fibers in the sense that it suggested the geometrical relation of core and number of waveguides, but the attenuation was still high at 1 decibel per meter. Therefore, Snitzer's invention was more suitable for medical instruments that looked the inside parts of the human body. Telecommunication purpose fibers are required to carry optical signals longer distances and hence required an attenuation of less than 10 or 20 dB per kilometer. Copper cables had 20dB attenuation per kilometer. Optical fibers are useful if they can compete with copper.

Dr. Charles K. Kao identified the need for the 10 or 20 dB of light loss per kilometer for an optical fiber to be used for long distance telecommunication. Dr K. Kao put forward his theory in 1964. Dr. Kao successfully proved the need for a purer form of glass to help reduce light loss.

A team of communication researchers were experimenting with fused silica in Corning’s lab. Silica is a material capable of extreme purity with a high melting point and a low refractive index. Corning Glass researchers Robert Maurer, Donald Keck, and Peter Schultz invented fiber optic wire or optical waveguide fibers. This newly invented Optical fiber could carry 65,000 times more information than copper wire.

The Corning’s research team could solve the decibel loss problem pointed out by Dr. Kao. Corning could thus develop a single mode fiber, SMF with a loss of 17 dB/km at 633 nm. This they achieved by doping titanium into the core of the optical fiber.

Peter Schultz Robert, Maurer and Donald Keck invented germanium doped multimode fiber in 1972. This multimode fiber was with a loss of 4 dB per kilometer and much greater strength than titanium doped fiber., John MacChesney developed a modified chemical vapor deposition process, MCVD process for manufacturing the preform, the raw material of fiber, at Bell Labs in1973. With the invention of MCVD process, the commercial production of optical fiber started.

Our internet resources said, The General Telephone and Electronics tested and deployed the world's first live telephone traffic through a fiber-optic system running at 6 Mbps, at Long Beach, California In April 1977. Bell in May 1977, installed an optical telephone communication system in the downtown Chicago area, covering a distance of 2.4 kilometers. Each pair of optical fiber carried the equivalent of 672 voice channels and this was equivalent to a DS3 circuit.

Today optical fiber cables carry more than 80 percent of the long distance voice and data traffic all over the world. The fiber has virtually penetrated to every walks of the life. Looking back to the historical days, the efforts of the great people who made this mode of communication possible, has contributed to the fast modernization of the human civilizations around the world by revolutionizing the information technology.