Fiber optic cables transmit information using pulses of light rather than electrical signals. Light pulses traveling through the fiber optic core can carry various types of data such as video, audio, or computer information. Fiber optic cables have several advantages over traditional copper wires including higher speeds, greater bandwidth, and less susceptibility to electromagnetic interference.

1. How it works:
A glass tunnel through which the light travels is
created. When the light hits the cladding, it interacts
with and reflects back into the core. Because of this
design, the light can “bend” around curves in the fiber
and makes it possible to travel further distances without
having to be repeated.
The light that travels along the fiber is made up of a
binary code that pulses “on” and “off” and determines
what information a given signal contains. The
advantage of fiber is that these on/off pulses can be:
translated video, computer, or voice data depending on
the type of transmitter and receiver used.
Facts About Fiber Optics
Fiber optics were needed because television cables were
becoming more capable of carrying more information
than copper wire so computer and telephone companies
needed something to compete.
Currently all new undersea cables are made of optical
fibers.
Experts say that sometime in the early 21st century,
98% of copper wire will be replaced by fiber optic cable.
Fiber optic cable installed for copper wire that already
needs replacing is less expensive since it only needs
repeaters to amplify the signals running through it
every six miles rather than every mile.
Optical fiber phone lines cannot be bugged or tapped.
A fiber is thinner than a human hair.
Advantages of Fiber Optic Cables Over
Glossary of Fiber Terms
LAN & WAN Applications

2. Copper
Speed: Fiber optic networks operate at speeds up to 10
gigabits per second or higher, as opposed to 1.54
megabits per second for copper. A fiber optic system is
now capable of transmitting the equivalent of an entire
encyclopedia (24 volumes) of information in one
second. Fiber can carry information so fast that you
could transmit three television episodes in one second.
Bandwidth: Taken in bulk, it would take 33 tons of
copper to transmit the same amount of information
handled by 1/4 pound of optical fiber.
Resistance: Fiber optic cables have a greater
resistance to electromagnetic noise such as radios,
motors or other nearby cables. Because optical fibers
carry beams of light, they are free of electrical noise
and interference.
Capacity: Fiber optics have a greater capacity for
information which means smaller cables can be used.
An optical fiber cable the size of an electrical cord can
replace a copper cable hundreds of times thicker.
Why Fiber Optics?
LAN's developed as a
result to the information
explosion that occurred
in the late 1980's. The
need for office,
laboratory, and factory
computers to share
information became
essential. Since the
1980's, many media
have been developed for
use in LAN's, each
meeting a specific user
demand. Glass fiber was
developed for use in
long distance, high
bandwidth applications,
but the high cost of
hardware and
installation has daunted
users.
Twisted pair, on the
other hand, was
developed as a low cost

3. alternative medium for
use in shorter distance
applications. Twisted
pair seemed to be an
ideal medium for
LAN's, but as computer
graphics have become
more "graphic
intensive", LAN's have
been required to
transmit a much greater
volume of information,
requiring a media with a
much higher bandwidth.
Since twisted pair is not
capable of supporting
the higher signaling
rates, there has been an
increased interest in
developing a low cost
fiber solution.
Types of Optical Fibers & Cables
The differences among
fibers is their core
sizes (the lightcarrying region of the
fiber). Multi-mode
fiber has much larger
core than Singlemode
fiber. Multi-mode
fibers have a combined
diameter in the 501000 um range. (where
um is a micron and one
micron is 1/250th the
width of a human
hair). Each fiber in a
Multi-mode cable is
capable of carrying a
different signal
independent from
those on the other
fibers in the cable
bundle. These larger
core sizes generally
have greater
bandwidth and are

4. easier to couple and
interconnect. It allows
hundreds of rays to
light to propagate
through the fiber
simultaneously. Multimode fiber today is
used primarily in
premise applications,
where transmission
distances are less than
two kilometers.
Singlemode fiber glass
has a much smaller
core that allows only
one mode of light to
propagate through the
core. Singlemode fiber
has a higher bandwidth
and less loss than
Multi-mode fiber and
for this reason it is the
ideal transmission
medium for many
applications. The
standard Singlemode
fiber core is
approximately 8-10
um in diameter.
Because of its greater
information-carrying
capacity, Singlemode
fiber is typically used
for longer distances
and higher-bandwidth
applications.
While is might appear
that Multi-mode fibers
have higher
information carrying
capacity, this is not the
case. Singlemode
fibers retain the
integrity of each light
pulse over longer
distances which allows
more information to be
transmitted. This is

5. why Multi-mode fibers
are used for shorter
distances.
POF-or Plastic Optical Fiber-is a newer plastic-based
cable which promises performance similar to
Singlemode Cable, but at a lower cost. POF is still in the
infancy stage although many companies are noticing its
potential.
An Application of Fiber Optics
Ok, you are probably wondering how fiber optics is used
in every day life.
ENCODING---->TRANSMIT--->DECODING
Take for example, your basic telephone conversation. In
the fiber optic telecommunication system, a message is
sent from one end through an electric cable to an
encoder which transmits a signal through a glass fiber
optic cable. It then travels through a repeater, back
through the cable, into a decoder and through an
electric cable into the phone line on the other end. The
sound waves that your voice generates becomes wave
of electricity in the mouthpiece of your telephone.
Rather than electricity flowing through copper wire to
your destination, fiber optics allows electricity to pass
through the encoder which measures the waves of
electricity 8000 times each second. The encoder then
converts these waves into "on"/"off" pulses of infrared
light that are digitized allowing them to be read by the
telephone system. Receiving the digitized message is
the decoder. This device converts the laser light back
into electrical waves. These electrical waves are
changed into the sound that we hear through the
phone. This same process not only works for the
telephone, but also other sources that transmit data
(i.e. computers, televisions).
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