Physical Transmission Media

Physical Transmission Media

8

04/22/231 Modified by: Brierley

Objectives

In this chapter, you will learn to:

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


Characteristics of Wireline Transmission

Impedance: expressed in Ohms, is the combined effect of a circuit’s inductance and capacitance.

Propagation Delay and Latency: the difference in time between a data packet’s transmission and its reception over a specific route.

Distortion: the unintended and undesirable modification of at least one signal component, which makes the signal different from how it was originally transmitted.

Noise: any unwanted interference from external sources.


Crosstalk


Impulse Noise


Thermal Noise


Coaxial Cable


Non-twisted Wire


Level 1 Terminations


Twisted Pair (TP)


Shielded Twisted Pair (STP)


Unshielded Twisted Pair (UTP)


Category 5 (CAT5)


Category 3 (CAT3)


You describe and draw

Fiber Optic Cable


Popular Uses for Fiber Optic Cable

Includes connecting:

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

switching systems, such as PBX


Selecting Appropriate Media

When selecting telecommunications media consider:

Existing infrastructure Throughput potential Cost of installation Noise immunity Security Size and scalability


Comparison of Physical Media


Structured Cabling


Backbone Wiring


Telecommunications Closet


Horizontal Wiring


Work Area


Installing UTP


Crossover Cable


Installation Tips for CAT5 UTP

Do not untwist twisted-pair cables more than one-half inch before inserting them into the punch-down block or connector.

Pay attention to the bend radius limitations for the type of cable you are installing.

Test each segment of cabling as you install it with a cable tester.

Use only cable ties to cinch groups of cables together04/22/2330 Modified by: Brierley

Installation Tips for CAT5 UTP

When pulling cable, do not exert more than 25 pounds of pressure on the cable.

Avoid laying cable across the floor where it might sustain damage from rolling chairs or foot traffic.

Install cable at least three feet away from fluorescent lights or other sources of EMI.

Always leave slack in cable runs.


Installing Fiber

Splice - the physical joining of two facing and aligned pieces of wire or fiber.

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.

Fusion splicing - a connection between fibers is accomplished through the application of heat and the resulting melting and fusion of two fiber strands.


Mechanical and Fusion Splicing


ST and SC Fiber Connectors


Cable Installation Tips for Fiber Optic Cable

When pulling fiber optic cable, do not exert pressure on the cable.

Fiber optic cable should be installed within a conduit whenever you are concerned about the potential for environmental damage.

Do not exceed the minimum bend radius.


Troubleshooting Connectivity Problems

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


Troubleshooting Tools

Crossover Cable - allows you to quickly and easily verify that a node’s network adapter is transmitting and receiving signals properly.

Tone Generator - a small electronic device that issues a signal on a wire pair.

Tone Locator - a type of amplifier that can detect the inductive energy emitted by the tone (current) on a wire.


Tone Generator and Tone Locator


Performance Testers

Provides the following functions:

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


Performance Testers


Fiber Optic Cable Testers


Time Domain Reflectometers


Telephone Test Set


Summary

Characteristics that affect wireline transmission include impedance changes, latency, delay distortion, and noise.

Traditional four-pair, non-twisted copper telephone wiring is known as Level 1 cable or quad wire.

Category (CAT3) UTP cable is the minimum grade of unshielded twisted-pair cabling for use in telephone systems.

To identify the source of cabling infrastructure problems, follow a logical troubleshooting methodology and have the appropriate testing tools handy.


Physical Transmission Media

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