Optical communication systems date back to the 1790s, to the optical semaphore telegraph
invented by French inventor Claude Chappe. In 1880, AlexanderGraham Bell patented an
optical telephone system, which he called the Photophone. However, his earlier invention, the
telephone, was more practical and took tangible shape. The Photophone remainedan
experimental invention and never materialized. During the 1920s, John Logie Baird in England
and Clarence W. Hansell in the United States patented the idea of using arrays of hollow pipes
ortransparent rods to transmit images for television or facsimile systems.
In 1954, Dutch scientist Abraham Van Heel and British scientist Harold H. Hopkins separately
wrote papers on imaging bundles.Hopkins reported on imaging bundles of unclad fibers,
whereas Van Heel reported on simple bundles of clad fibers. Van Heel covered a bare fiber
with a transparent cladding of a lower refractive index.This protected the fiber reflection
surface from outside distortion and greatly reduced interference between fibers.
Abraham Van Heel is also notable for another contribution. Stimulated by aconversation with
the American optical physicist Brian O'Brien, Van Heel made the crucial innovation of cladding
fiber-optic cables. All earlier fibers developed were bare and lacked any form of cladding,with
total internal reflection occurring at a glass-air interface. Abraham Van Heel covered a bare
fiber or glass or plastic with a transparent cladding of lower refractive index. This protectedthe total reflection surface from contamination and greatly reduced cross talk between fibers.
By 1960, glass-clad fibers had attenuation of about 1 decibel (dB) per meter, fine for medical
imaging,but much too high for communications. In 1961, Elias Snitzer of American Optical
published a theoretical description of a fiber with a core so small it could carry light with only