Basics Of Fiber Optic Cable and How Fiber Optics Work
American Tele Data
has provided you a "how fiber optics work"
basics page to show a brief overview of how Fiber Optic Cable
Advantages over Copper Cable as well as a resource for other fiber
optic cable and technology developments and basics - such as fiber
optic cable design and WDM's or wave division
multiplexing where you can get "more bandwidth for your buck"
without adding additional fiber optic cable. Always feel free
to come back to our site for additional information on fiber optic
technology. We will also always be glad to help you with any questions
you may have regarding fiber optics. Fiber optic cable functions
as a "light guide," guiding the light introduced at
one end of the cable through to the other end. The light source
can either be a light-emitting diode (LED)) or a laser.The light
source is pulsed on and off, and a light-sensitive receiver on
the other end of the cable converts the pulses back into the digital
ones and zeros of the original signal. Even
laser light shining through a fiber optic cable is subject to
loss of strength, primarily through dispersion and scattering
of the light, within the cable itself. The faster the laser fluctuates,
the greater the risk of dispersion. Light strengtheners, called
repeaters, may be necessary to refresh the signal in certain applications.
TO EXTEND YOUR ETHERNET SIGNAL MORE THAN 300 FEET USING FIBER
SPEED: Fiber optic networks operate at high speeds - up
into the gigabits
BANDWIDTH: large carrying capacity
DISTANCE: Signals can be transmitted further without
needing to be "refreshed" or strengthened.
RESISTANCE: Greater resistance to electromagnetic
noise such as radios, motors or other nearby cables.
MAINTENANCE: Fiber optic cables costs much less
are three types of fiber optic cable commonly used: single mode, multimode
and plastic optical fiber (POF).
glass or plastic fibers which allow light to be guided from one end to the other
with minimal loss.
Fiber optic cable functions as a "light guide," guiding the light introduced
at one end of the cable through to the other end. The light source can either
be a light-emitting diode (LED)) or a laser.
light source is pulsed on and off, and a light-sensitive receiver on the other
end of the cable converts the pulses back into the digital ones and zeros of the
laser light shining through a fiber optic cable is subject to loss of strength,
primarily through dispersion and scattering of the light, within the cable itself.
The faster the laser fluctuates, the greater the risk of dispersion. Light strengtheners,
called repeaters, may be necessary to refresh the signal in certain applications.
fiber optic cable itself has become cheaper over time - a equivalent length of
copper cable cost less per foot but not in capacity. Fiber optic cable connectors
and the equipment needed to install them are still more expensive than their copper
Mode cable is a single stand of glass fiber with a diameter of 8.3 to 10 microns
that has one mode of transmission.
Single Mode Fiber with a relatively narrow
diameter, through which only one mode will propagate typically 1310 or 1550nm.
Carries higher bandwidth than multimode fiber, but requires a light source with
a narrow spectral width. Synonyms mono-mode optical fiber, single-mode fiber,
single-mode optical waveguide, uni-mode fiber.
fiber gives you a higher transmission rate and up to 50 times more distance than
multimode, but it also costs more. Single-mode fiber has a much smaller core than
multimode. The small core and single light-wave virtually eliminate any distortion
that could result from overlapping light pulses, providing the least signal attenuation
and the highest transmission speeds of any fiber cable type.
optical fiber is an optical fiber in which only the lowest order bound mode can
propagate at the wavelength of interest typically 1300 to 1320nm.
jump to single mode fiber page
Multimode cable is made of of glass fibers, with a common diameters in the 50-to-100
micron range for the light carry component (the most common size is 62.5). POF
is a newer plastic-based cable which promises performance similar to glass cable
on very short runs, but at a lower cost.
fiber gives you high bandwidth at high speeds over medium distances. Light waves
are dispersed into numerous paths, or modes, as they travel through the cable's
core typically 850 or 1300nm. Typical multimode fiber core diameters are 50, 62.5,
and 100 micrometers. However, in long cable runs (greater than 3000 feet [914.4
ml), multiple paths of light can cause signal distortion at the receiving end,
resulting in an unclear and incomplete data transmission.
10 billion digital bits can be transmitted per second along an optical fiber link
in a commercial network, enough to carry tens of thousands of telephone calls.
Hair-thin fibers consist of two concentric layers of high-purity silica glass
the core and the cladding, which are enclosed by a protective sheath. Light rays
modulated into digital pulses with a laser or a light-emitting diode move along
the core without penetrating the cladding.
light stays confined to the core because the cladding has a lower refractive indexa
measure of its ability to bend light. Refinements in optical fibers, along with
the development of new lasers and diodes, may one day allow commercial fiber-optic
networks to carry trillions of bits of data per second.
Total internal refection confines light within optical fibers (similar to looking
down a mirror made in the shape of a long paper towel tube). Because the cladding
has a lower refractive index, light rays reflect back into the core if they encounter
the cladding at a shallow angle (red lines). A ray that exceeds a certain "critical"
angle escapes from the fiber (yellow line).
has a large core, up to 100 microns in diameter. As a result, some of the light
rays that make up the digital pulse may travel a direct route, whereas others
zigzag as they bounce off the cladding. These alternative pathways cause the different
groupings of light rays, referred to as modes, to arrive separately at a receiving
point. The pulse, an aggregate of different modes, begins to spread out, losing
its well-defined shape. The need to leave spacing between pulses to prevent overlapping
limits bandwidth that is, the amount of information that can be sent. Consequently,
this type of fiber is best suited for transmission over short distances, in an
endoscope, for instance.
contains a core in which the refractive index diminishes gradually
from the center axis out toward the cladding. The higher refractive index at the
center makes the light rays moving down the axis advance more slowly than those
near the cladding. Also, rather than zigzagging off the cladding, light in the
core curves helically because of the graded index, reducing its travel distance.
The shortened path and the higher speed allow light at the periphery to arrive
at a receiver at about the same time as the slow but straight rays in the core
axis. The result: a digital pulse suffers less dispersion.
FIBER has a narrow
core (eight microns or less), and the index of refraction between the core and
the cladding changes less than it does for multimode fibers. Light thus travels
parallel to the axis, creating little pulse dispersion. Telephone and cable television
networks install millions of kilometers of this fiber every year.
- Two basic cable designs are:
cable, used in the majority of outside-plant installations in North America, and
tight-buffered cable, primarily used inside buildings.
modular design of loose-tube cables typically holds up to 12 fibers per buffer
tube with a maximum per cable fiber count of more than 200 fibers. Loose-tube
cables can be all-dielectric or optionally armored. The modular buffer-tube design
permits easy drop-off of groups of fibers at intermediate points, without interfering
with other protected buffer tubes being routed to other locations. The loose-tube
design also helps in the identification and administration of fibers in the system.
tight-buffered cables are used as pigtails, patch cords and jumpers to terminate
loose-tube cables directly into opto-electronic transmitters, receivers and other
active and passive components.
tight-buffered cables also are available and are used primarily for alternative
routing and handling flexibility and ease within buildings.
2 - Loose-Tube
a loose-tube cable design, color-coded plastic buffer tubes house and protect
optical fibers. A gel filling compound impedes water penetration. Excess fiber
length (relative to buffer tube length) insulates fibers from stresses of installation
and environmental loading. Buffer tubes are stranded around a dielectric or steel
central member, which serves as an anti-buckling element.
cable core, typically uses aramid yarn, as the primary tensile strength member.
The outer polyethylene jacket is extruded over the core. If armoring is required,
a corrugated steel tape is formed around a single jacketed cable with an additional
jacket extruded over the armor.
cables typically are used for outside-plant installation in aerial, duct and direct-buried
3 - Tight-Buffered Cable
tight-buffered cable designs, the buffering material is in direct contact with
the fiber. This design is suited for "jumper cables" which connect outside
plant cables to terminal equipment, and also for linking various devices in a
tight-buffered cables often are used for intra-building, risers, general building
and plenum applications.
tight-buffered design provides a rugged cable structure to protect individual
fibers during handling, routing and connectorization. Yarn strength members keep
the tensile load away from the fiber.
with loose-tube cables, optical specifications for tight-buffered cables also
should include the maximum performance of all fibers over the operating temperature
range and life of the cable. Averages should not be acceptable.
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links below as we have a complete array of fiber optic cables including singlemode
fiber optic cable, multimode fiber optic cable, loose tube fiber cable, indoor-
outdoor fiber optic cable, multimode fiber optic cable, central office fiber optic
cable, military (Milspec) fiber optic cable, freedom fiber optic cable, altos
fiber optic cable, dielectric cable, specialty fiber optic cable and a complete
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