文档介绍：C HAPTER
1
THE ORIGINS OF
FIBER OPTIC
COMMUNICATIONS
JEFF HECHT
munication systems date back two centuries, to the “optical tele-
graph” invented by French engineer Claude Chappe in the 1790s. His system was
a series of semaphores mounted on towers, where human operators relayed mes-
sages from one tower to the next. It beat hand-carried messages hands down, but
by the mid-19th century it was replaced by the electric telegraph, leaving a scat-
tering of “telegraph hills” as its most visible legacy.
Alexander Graham Bell patented an optical telephone system, which he
called the Photophone, in 1880, but his earlier invention, the telephone, proved
far more practical. He dreamed of sending signals through the air, but the
atmosphere did not transmit light as reliably as wires carried electricity. In the
decades that followed, light was used for a few special applications, such as sig-
naling between ships, but otherwise munications, such as the experi-
mental Photophone Bell donated to the Smithsonian Institution, languished on
the shelf.
Thanks to the Alfred P. Sloan Foundation for research support. This is a much expanded
version of an article originally published in the November 1994 Laser Focus World.
1
2 CHAPTER 1 — THE ORIGINS OF FIBER MUNICATIONS
In the intervening years, a new technology that would ultimately solve the
problem of optical transmission slowly took root, although it was a long time
before it was adapted munications. This technology depended on the phe-
nomenon of total internal reflection, which can confine light in a material sur-
rounded by other materials with lower refractive index, such as glass in air.
In the 1840s, Swiss physicist Daniel Collodon and French physicist Jacques
showed that light could be guided along jets of water for fountain dis-
plays. British physicist John Tyndall popularized light guiding in a demonstration
he first used in 1854, guiding light in a jet of water flowing fr