Physical Transmission
Media
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Objectives
In this chapter, you will learn to:
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Characteristics of wireline transmission
Properties and uses of coaxial cable
Properties and uses of different types of twisted-pair wire
Characteristics of lightwave transmission
Properties and uses of fiber optic cable
Factors to consider when selecting a telecommunications
medium
Cabling standards
Installing wire and fiber optic cabling
Testing continuity and performance on physical transmission
media
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Characteristics of Wireline
Transmission
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Impedance: expressed in Ohms, is the combined
effect of a circuit’s inductance and capacitance.
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Propagation Delay and Latency: the difference
in time between a data packet’s transmission and its
reception over a specific route.
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Distortion: the unintended and undesirable
modification of at least one signal component, which
makes the signal different from how it was originally
transmitted.
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Noise: any unwanted interference from external
sources.
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Crosstalk
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Impulse Noise
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Thermal Noise
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Coaxial Cable
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Non-twisted Wire
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Level 1 Terminations
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Twisted Pair (TP)
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Shielded Twisted Pair (STP)
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Unshielded Twisted Pair (UTP)
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Category 5 (CAT5)
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Category 3 (CAT3)
You describe and draw
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Fiber Optic Cable
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Fiber Optic Cable
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Popular Uses for Fiber Optic Cable
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Includes connecting:
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Regional and local cable TV facilities
Internet NAPs with other large
telecommunications exchange point
Central offices with other central offices
Main feeders with central offices
A telecommunication’s network with private
LANs
A telecommunication’s network with private
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switching systems,
such as PBX
Selecting Appropriate Media
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When selecting telecommunications media
consider:
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Existing infrastructure
Throughput potential
Cost of installation
Noise immunity
Security
Size and scalability
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Comparison of Physical Media
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Comparison of Physical Media
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Structured Cabling
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Backbone Wiring
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Telecommunications Closet
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Telecommunications Closet
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Horizontal Wiring
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Work Area
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Work Area
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Installing UTP
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Crossover Cable
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Installation Tips for CAT5 UTP
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Do not untwist twisted-pair cables more than one-half
inch before inserting them into the punch-down block
or connector.
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Pay attention to the bend radius limitations for the
type of cable you are installing.
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Test each segment of cabling as you install it with a
cable tester.
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Use only cable ties to cinch groups of cables together
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Installation Tips for CAT5 UTP
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When pulling cable, do not exert more than 25
pounds of pressure on the cable.
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Avoid laying cable across the floor where it
might sustain damage from rolling chairs or foot
traffic.
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Install cable at least three feet away from
fluorescent lights or other sources of EMI.
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Always leave slack
in cable runs.
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Installing Fiber
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Splice - the physical joining of two facing and
aligned pieces of wire or fiber.
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Mechanical splicing - the two ends of a
fiber optic cable are fixed in position within a
tube so that they form one continuous
communications channel.
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Fusion splicing - a connection between
fibers is accomplished through the application
of heat and the resulting melting and fusion of
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two fiber strands.
Mechanical and Fusion Splicing
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ST and SC Fiber Connectors
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Cable Installation Tips for Fiber
Optic Cable
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When pulling fiber optic cable, do not exert
pressure on the cable.
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Fiber optic cable should be installed within a
conduit whenever you are concerned about the
potential for environmental damage.
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Do not exceed the minimum bend radius.
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Troubleshooting Connectivity
Problems
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Identify the symptoms
Identify the scope of the problem
Establish what has changed on the network
Determine the most probable cause of the
problem
Implement a solution
Test the solution
Recognize the potential effects of the solution
Document the solution
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Troubleshooting Tools
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Crossover Cable - allows you to quickly and
easily verify that a node’s network adapter is
transmitting and receiving signals properly.
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Tone Generator - a small electronic device that
issues a signal on a wire pair.
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Tone Locator - a type of amplifier that can detect
the inductive energy emitted by the tone (current) on
a wire.
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Tone Generator and Tone Locator
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Performance Testers
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Provides the following functions:
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Measures the length of each wire pair
Ensures that the cable does not exceed
recommended maximum lengths
Measures the distance from the tester to a
cable fault
Measures attenuation along a cable
Measures crosstalk between wires
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Performance Testers
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Fiber Optic Cable Testers
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Time Domain Reflectometers
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Telephone Test Set
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Summary
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Characteristics that affect wireline transmission include
impedance changes, latency, delay distortion, and noise.
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Traditional four-pair, non-twisted copper telephone wiring
is known as Level 1 cable or quad wire.
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Category (CAT3) UTP cable is the minimum grade of
unshielded twisted-pair cabling for use in telephone
systems.
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To identify the source of cabling infrastructure problems,
follow a logical troubleshooting methodology and have
the appropriate testing tools handy.
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