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What is fiber optics cable?
A fiber optic cable is a network cable that contains strands of glass fibers inside an insulated casing.
These cables are designed for long distance and very high bandwidth (gigabit speed) network
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How it works?
To understand how a fiber optic cable works, imagine an immensely long drinking straw or flexible
plastic pipe. For example, imagine a pipe that is several miles long. Now imagine that the inside
surface of the pipe has been coated with a perfect mirror. Now imagine that you are looking into
one end of the pipe. Several miles away at the other end, a friend turns on a flashlight and shines
it into the pipe. Because the interior of the pipe is a perfect mirror, the flashlight's light will reflect
off the sides of the pipe (even though the pipe may curve and twist) and you will see it at the other
end. If your friend were to turn the flashlight on and off in a Morse code fashion, your friend could
communicate with you through the pipe. That is the essence of a fiber optic cable.
Making a cable out of a mirrored tube would work, but it would be bulky and it would also be hard
to coat the interior of the tube with a perfect mirror. A real fiber optic cable is therefore made out
of glass. The glass is incredibly pure so that, even though it is several miles long, light can still make
it through (imagine glass so transparent that a window several miles thick still looks clear). The glass
is drawn into a very thin strand, with a thickness comparable to that of a human hair. The glass
strand is then coated in two layers of plastic. By coating the glass in plastic, you get the equivalent
of a mirror around the glass strand. This mirror creates total internal reflection, just like a perfect
mirror coating on the inside of a tube does.
Fiber type Wave length (nm) Max attenuation
50/125 (OM2, OM3,
850 3.5 500, 2000, 3500
1300 1.5 500
62.5/125 (OM1) 850 3.5 160
1300 1.5 500
OS2) – premises
1310 1.0 NA
1550 1.0 NA
OS2) – outside plant
1310 0.5 NA
1550 0.5 NA
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Types of fiber optics cables
1. Simplex Cable
Single strand of fiber surrounded by a 900 um buffer then a layer of Kevlar and finally the outer
jacket. Available in 2mm or 3mm and Plenum or Riser Jacket. Plenum is stronger and made to
charge in fire versus riser is made to melt in fire. Riser cable is more flexible.
2. Duplex Cable
In data communications, the simultaneous operation of a circuit in both directions is known as full
duplex; if only one transmitter can send at a time, the system is called half duplex.
Two single strands of fiber optic cable attached at the center. Surrounded by a 900 um buffer then
a layer of Kevlar and finally the outer jacket. Available in 2mm or 3mm and Plenum or Riser Jacket.
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3. Fiber Optic Ribbon
A coherent optical fiber bundle in which the configuration is flat rather than round, giving an output
in a line. Fiber optic ribbon cable is available bare (without a jacket or Kevlar and also available
with a plenum jacket or riser jacket. A typical ribbon has 12 color coded fibers and cables can be
made with multiple ribbons. The jackets on ribbon cable are oval and can be broken out into fan
out assemblies providing individual single connectors or using a MTP connector for multiple fibers
being terminated with one connector.
4. Loose Tube
Loose Tube are 250 um fibers inside of a smooth tube normally submerged in a water resistant gel
but can be dry. The tubes (normally multiple) are then surrounded by a water resistant tape and
all tubes are incased inside a protective outer jacket. There are many different types and fiber
counts. Depending on how ordered, some tubes may be empty.
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Why use fiber optics over copper?
Networking companies use fiber to connect all their central offices and long distance switches
because it has thousands of times the bandwidth of copper wire and can carry signals hundreds of
times further before needing a repeater. The communication companies use fiber because it give
them greater reliability and the opportunity to offer new services, like phone service and Internet
connections. Both Networking companies and communication operators use fiber for economic
reasons, but their cost justification requires adopting new network architectures to take advantage
of fiber's strengths. A properly designed premises cabling network can also be less expensive when
done in fiber instead of copper.
Speed of fiber optics cables
Transmission speeds can be extremely high. For example, recently a 160Km length of cable carried
information at 14,000 Gigabits / sec. This kind of performance is used in oceanic cables that connect
University of Southampton researchers have created fibers that can transmit data at 99.7% the
speed of light. That means data can be transmitted up to incredible speeds like 73.7 terabits per
second, but what it doesn’t mean is a faster Internet connection for us common folk.
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Advantages of fiber optic cables
Extremely high bandwidth
Fiber optics cables provides a higher bandwidth over any other transition media.
Fiber provides an extremely secure transmission medium, as there is no way to detect
the data being transmitted by “listening in” to the electromagnetic energy “leaking”
through the cable, as is possible with traditional, electron-based transmissions. By
constantly monitoring an optical network and by carefully measuring the time it takes
light to reflect down the fiber, splices in the cable can be easily detected.
Immunity and reliability
Fiber provides extremely reliable data transmission. It’s completely immune to many
environmental factors that affect copper cable. The core is made of glass, which is an
insulator, so no electric current can flow through. It’s immune to electrometric
interference and radio-frequency interference (EM/RFI), crosstalk, impedance
problems, and more. You can run fiber cable next to industrial equipment without
worry. Fiber is also less susceptible to temperature fluctuations than copper and can
be submerged in water.
Resistance to electromagnetic interference
Fiber has a very low rate of bit error (10 EXP-13), as a result of fiber being so resistant
to electromagnetic interference. Fiber-optic transmission are virtually noise free.
Several miles of optical cable can be made cheaper than equivalent lengths of copper
wire. This saves your provider (cable TV, Internet) and you money.
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Less signal degradation
The loss of signal in optical fiber is less than in copper wire. Light signals - Unlike
electrical signals in copper wires, light signals from one fiber do not interfere with
those of other fibers in the same cable. This means clearer phone conversations or TV
Because no electricity is passed through optical fibers, there is no fire hazard.
Because signals in optical fibers degrade less, lower-power transmitters can be used
instead of the high-voltage electrical transmitters needed for copper wires. Again,
this saves your provider and you money.
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Disadvantages of fiber optic cables
Installation costs, while dropping, are still high
Despite the fact that fiber installation costs are dropping by as much as 60% a year,
installing fiber optic cabling is still relatively costly. As installation costs decrease, fiber
is expanding beyond its original realm and major application in the carrier backbone
and is moving into the local loop, and through technologies such as FTTx (Fiber to
the Home, Premises, etc.,) and PONs (Passive Optical networks), enabling subscriber
and end user broadband access.
Susceptibility to physical damage
Fiber is a small and compact cable, and it is highly susceptible to becoming cut or
damaged during installation or construction activities. Because railroads often
provide rights-of-way for fiber optic installation, railroad car derailments pose a
significant cable damage threat, and these events can disrupt service to large groups
of people, as fiber optic cables can provide tremendous data transmission
capabilities. Because of this, when fiber optic cabling is chosen as the transmission
medium, it is necessary to address restoration, backup and survivability.
Special test equipment is often required
The test equipment typically and traditionally used for conventional electron-based
networking is of no use in a fiber optic network. Equipment such as an OTDR (Optical
Time Domain Reflect meter) is required, and expensive, specialized optical test
equipment such as optical probes are needed at most fiber endpoints and connection
nexuses in order to properly provide testing of optical fiber.
Fibers can be broken or have transmission loses when wrapped around curves of only
a few centimeters radius. However by encasing fibers in a plastic sheath, it is difficult
to bend the cable into a small enough radius to break the fiber.