Fiber Optics Overview!  

What is Fiber Optics

While this class deals primarily with copper terminations in the
horizontal cable system, Pass & Seymour feels that it is appropriate to
convey a general understanding of fiber optic transmission and
components.

The telecommunications industry has placed a great deal of mystery
around fiber optic signal transmission, but fiber is really quite simple
when you break it down to the basics.

Fiber Optic signal transmission is simply a way of sending information in
the form of light. Much like Morse Code, pulses of light are transmitted
and received and translated into pieces of information. The light is sent
through strands of glass or plastic, thinner than the diameter of a
human hair.

Electrical current carrying data is converted to light pulses, sent through
the strand of glass, then converted back to electrical current at the
receiving end of the cable.

As light can only travel in one direction at a time, two strands of cable
are required one each to send and receive signals.

Transmitters and Receivers are located at each end of the fiber cable.
These devices transmit information and receives information in the form
of light pulses, which has been converted from electrical current.

Very often the transmitter and receiver is in the same component,
they're referred to as 'transceivers'.

 Fiber Optic Cable

A Fiber Optic Cable is a strand of glass that uses light pulses to
transmit information. These light pulses are converted from and to
electrical signals by networking electronics placed at each end of the
cable.

The construction of the cable consists of a center core of glass,
surrounded by glass of different reflecting properties called cladding.
The light is passed along this core, reflecting off of the cladding. The
core and cladding are surrounded by a bonded material called the
buffer that protects the glass. A strength member, usually made of
KevlaFM, surrounds the buffer and all of this is then encased in an outer
jacket.

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The material of the outer jacket is dependent upon where the cable is to
be run. Indoors or out, buried or aerial, plenum or riser etc.

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The key difference in types of optical fiber cable is the manner in which
light is sent through the cable.

Two distinct types of cable are single mode and multi-mode. Single
mode cable is typically used by service providers and for outside plant
installations, as it has longer distance capabilities. The core of single
mode cable is very thin, minimizing reflections on the cladding. A single
mode, or path, of light is generated by a laser. Because of the
precision electronics required for single mode fiber cable, the
associated costs are typically high.

Click to view / Multi Mode Paths

The most common type of Fiber Optic cable used in commercial
building communications is multi-mode. Multiple light paths are
generated from an LED, and the wider core allows all paths to transmit
simultaneously. The distance and information carrying capacity of
multi-mode fiber far exceeds the limits of copper, and makes this media
a wise choice for backbone installations.

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Common Fiber Types Used

In addition to the types of core/cladding that characterize fiber optic
cable, there are different buffers and jackets that distinguish types of
cable.

Cable construction; Tight Buffer refers to a construction that has a
900_m protective covering that tightly surrounds the glass, This is
typical for indoor applications as it provides good protection to the glass strand. This type of fiber does not perform well outdoors with severe temperature changes, rain, wind etc. Outdoor installations require loose tube construction. This construction actually has a tight buffer too, but it is only 250_m in diameter. Multiple strands of glass buffered to 250_m are then placed into a plastic tube. The plastic tubes get filled with a petroleum based gel. The combination of the tubes and gel provides physical protection for the glass strands and enough room for them to move when subjected to environmental extremes.

This petroleum based gel will propagate a flame, one of the reasons
loose tube cable must be converted to indoor rated cable within 50 feet
of entering a building.

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For a Total
Fiber Optic CableTutorial 
Vist: arcelect.com