Fiber Optics


Fiber Optic Cable Facts

"A relatively new technology with vast potential importance, fiber optics is the
channeled transmission of light through hair-thin glass fibers."

[ Less expensive than copper cables

[ Raw material is silica sand

[ Less expensive to maintain If damaged, restoration time is faster
(although more users are affected)

[ Backbone to the Information Superhighway

Information (data and voice) is transmitted through the fiber digitally by
the use of high speed LASERs (Light Amplification through the Simulated Emission
of Radiation) or LEDs (Light Emitting Diodes). Each of these methods create a
highly focused beam of light that is cycled on and off at very high speeds.
Computers at the transmitting end convert data or voice into "bits" of
information. The information is then sent through the fiber by the presence, or
lack, of light. Computers on the receiving end convert the light back into data
or voice, so it can be used.

ORIGIN OF FIBER OPTICS

Information (data and voice) is transmitted through the fiber digitally by
the use of high speed LASERs (Light Amplification through the Simulated Emission
of Radiation) or LEDs (Light Emitting Diodes). Each of these methods create a
highly focused beam of light that is cycled on and off at very high speeds.
Computers at the transmitting end convert data or voice into "bits" of
information. The information is then sent through the fiber by the presence, or
lack, of light. So, all of the data is sent light pulses. Computers on the
receiving end convert the light back into data or voice, so it can be used.

All of this seems to be a very "modern" concept, and the technology we use
is. The concept though, was the idea of Alexander Graham Bell in the late 1800\'s.
He just didn\'t have a dependable light source... some days the sun doesn\'t
shine! He thought of the idea that our voices could be transmitted by pulses of
light. The people who thought that audio, video, and other forms of data could
be transmitted by light through cables, were present day scientists. Most of
the things that are possible today, Alexander Grahm Bell could never even have
dreamed of.

Although the possibility of lightwave communications occurred to Alexander
Graham Bell (who invented the telephone), his ideas couldn\'t be used until the
LASER or LED had been invented. Most of these advances occurred in the 1970s,
and by 1977 glass-purifying and other fiber-optic manufacturing techniques had
also reached the stage where interoffice lightwave communications were possible.
With further technological development, many intercity routes were in operation
by 1985, and some transoceanic routes had been completed by 1990. Now, in the
mid-90\'s, worldwide connections are possible through the Internet.

The light is prevented from escaping the fiber by total internal
reflection, a process that takes place when a light ray travels through a medium
with an Index of Refraction higher than that of the medium surrounding it. Here
the fiber core has a higher refractive index than the material around the core,
and light hitting that material is reflected back into the core, where it
continues to travel down the fiber.

THE PROPAGATION OF LIGHT AND LOSS OF SIGNALS

The glass fibers used in present-day fiber-optic systems are based on
ultrapure fused silica (sand). Fiber made from ordinary glass is so dirty that
impurities reduce signal intensity by a factor of one million in only about 16
ft of fiber. These impurities must be removed before useful long-haul fibers can
be made. But even perfectly pure glass is not completely transparent. It weakens
light in two ways. One, occurring at shorter wavelengths, is a scattering caused
by unavoidable density changes within the fiber. In other words, when the light
changes mediums, the change in density causes interference. The other is a
longer wavelength absorption by atomic vibrations. For silica, the maximum
transparency, occurs in wavelengths in the near infrared, at about 1.5 m
(micrometers).

APPLICATIONS

Fiber-optic technology has been applied in many areas, although its
greatest impact has come in the field of telecommunications, where optical fiber
offers the ability to transmit audio, video, and data information as coded light
pulses. Fiber optics are also used in the field of medicine, all of the wire-
cameras and lights are forms of fiber optic cable. In fact, fiber optics have
quickly become the preferred mode of transmitting communications of all kinds.
Its advantages over older methods of transmitting data are many, and include
greatly increased carrying capacity (due to the very high frequency of light),
lower transmission losses, lower cost