History - from 3000 BC 1.1

Occasionally history is reshaped by a single invention that changes some aspect of our world or environment. Optical fiber is one of those landmark inventions that is having a positive influence on many technological developments world wide.

Humankind has communicated with light long before scientists invented the first low-loss optical fiber. Many thousands of years ago signal fires were lit on prehistoric hills. Ancient Egyptians reflected the sun’s light to send solar signals. Revolving lenses magnified small flames in lighthouses long before electricity was harnessed or Alexander Graham Bell said his historic words to Watson.

Naturally occurring glasses have been used by man as far back as there is archeological evidence. Glasses are known to be manufactured as early as 12,000 B.C.¹ The oldest pieces of glaze and glass were discovered in Egypt, but it is unclear whether they originated in the Middle East or in Asia. Initially, glasses were used only as decorative and ornamental objects, such as jewelry. As the techniques for manufacturing glass developed, so did practical applications. Vessels were manufactured through molding and pressing of the glass. The first known glass vessels date back to the reign of Thutmose III (1504-1450 B.C.).² 

The invention of glassblowing in the first century B.C. greatly increased the use of glass for practical applications. Applications extended from ornaments to vessels to windows. Glassblowing soon spread as the standard method of shaping glass until the 19th century. Skilled craftsmen further developed the techniques and tools used in glassblowing. A common technique utilized a hollow iron pipe approximately 4ft long with a fitted mouthpiece on one end. The craftsman, known as a “gaffer,” would collect a small amount of molten glass or “gather” on the far end of the pipe. The gaffer would mold the exterior of the gather on a paddle or metal plate. This shaping is known as “marvering.” When sufficiently cooled, the gaffer would blow into the pipe, thereby expanding the gather into a bubble or “parison.” Through reheating and marvering, the gaffer could control the form of the glass piece.³ Glass manufacturing developed into a major industry, and by the year 1903, a fully automated glass blowing machine had been perfected.

As glass was being developed for use primarily in vessels and window pane in the 1700 and 1800’s, other technologies were being developed for communication. In the 1790’s, Claude Chappe invented “optical telegraphy.” Using towers mounted on hilltops, messages could be relayed from tower to tower through light signals. This was eventually replaced in the mid-19th century by the electric telegraph. The idea of using light for a communication signal came up again in 1880 when Alexander Graham Bell patented the photophone, an optical telephone system.

Separately in 1870, John Tyndall demonstrated the principle of total internal reflection to the British Royal Society. This principle demonstrates how light could be directed around curves, illustrated by Tyndall through light traveling down a stream of pouring water. The concept of using light to send communication signals, the principle of total internal reflection, and the development of high purity glass were combined in the mid to late 1900’s into the field of fiber optics.

By the late 1950s, glass optical fibers were developed similar to those now used in science, medicine, and industry. During the 1950s, image-transmitting fibers were developed by Brian O’Brien at the American Optical Company and by Narinder S. Kapany and colleagues at the Imperial College of Science and Technology in London. Many credit Kapany with the invention of the glass-coated glass rod and coining the term fiber optics in 1956.

Glass-clad fibers had attenuation of about one decibel per meter by 1960, fine for medical imaging, but much too high for communications.⁴ Charles Kao and Charles Hockham, of Standard Telecommunication Laboratory in England, in 1966, published a paper proposing that optical fibers could be used as a transmission medium if their losses could be reduced to 20dB/km. They speculated that the current high losses of over 1000dB/km were the result of impurities in the glass, not of the glass itself. Reducing these impurities would produce low-loss fibers suited for communications.

In 1970, Robert Maurer and colleagues at Corning Glass Works produced the first fiber with losses under 20dB/km. By 1972 losses were reduced to 4dB/km in laboratory samples, well below the level Kao and Hockham suggested was required for a practical communication system. Today, losses in the best fibers are less than 0.2dB/km.

Application of glass and optics continues to grow at a rapid pace. As a leading manufacturer of fused silica glass products, Polymicro has taken high purity glass materials and optics to even higher levels in fields such as gas chromatography, capillary electrophoresis, and specialty fiber optics. Our flexible manufacturing process provides the product you need in diameters from 30mm to 6.5mm, in lengths from 1mm to several kilometers. Stringent in-line dimensional controls yield tolerances as tight as ±1mm. Polymicro began business in 1984 and is now the leading supplier in many specialized market applications of synthetic fused silica optical fiber, capillary tubing and precision synthetic fused silica components.

¹ G.W. Morey, The Properties of Glass, 2nd ed., Reinhold, New York, (1954)
² "Glass," Microsoft® Encarta® 97 Encyclopedia, Microsoft Corporation (1993-1996)
³ Reference the Internet at www.pennynet.org/glmuseum/glgloss.htm
⁴ See "History of Fiber Optics,” Jeff Hetcht at www.sff.net/people/Jeff.Hecht/index.html

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