Topic 7 - Guided Transmission Media.pdf

7/29/2019 Topic 7 - Guided Transmission Media.pdf

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1Sumati J. Singh

TRANSMISSION MEDIA

1/23/2013


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Classification2

1/23/2013Sumati J. Singh


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Wired Media3



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Twisted Pair

2 conductors (copper) , own insulation , twisted

1 used to carry signal

Other used for ground reference

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ece ver uses e erence e ween em Noise or crosstalk may affect both



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Noise on Parallel Lines5



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Noise on Twisted Lines6

By adding the twist, reduction in the noise effect.1/23/2013Sumati J. Singh


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Twisted Pair Generally color coded twisted pairs of insulated copper wires encased

in plastic sheath

Each wire has a diameter of 0.4 to 0.8 mm

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,

Higher quality

More expensive

Number of twists per foot/meter is called twist ratio.

More twists need more cable, may increase ATTENUATION.

Balance is needed b/w minimizing crosstalk and reducing attenuation



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Twisted Pair Various purposes

Designs vary in twist ratio,grade of copper used, type of

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.

1 to 4200 pairs can bepacked.

Modern networks use 4 pairspacked in together.



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Characteristics

Twisted pair is

Relatively inexpensive

Flexible

Eas to install

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Span significant distance before needing a repeater

Easily accommodates different topologies

Two categories : STP & UTP



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Shielded Twisted Pair Consists of twisted wire pairs that are not only

individually insulated, but also surrounded by a

shielding made of a metallic substance such as foil.

Sometimes braided copper shielding

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Acts as barrier to external EM forces



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Unshielded Twisted Pair Twisted wire pairs (insulated

individually) covered in a plasticsheath

No additional shieldin

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Less expensive

Less resistant to noise



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Standards TIA/EIA finalized specifications in 1991 named

TIA/EIA 568 TIA Telecommunications Industry Standards

EIA Electronic Industries Standards

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Divides twisted pair wiring in several categories

Catfrom 1 to 7



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TIA/EIA 568

Category Bandwidth Data Rate Digital/Analog Use

1 very low < 100 kbps Analog Telephone

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< z ps na og g a - nes

3 16 MHz 10 Mbps Digital LANs




7 600 MHz 600 Mbps Digital LANs1/23/2013Sumati J. Singh


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Cat 3 vs Cat 5Apart from the listed differences, some visual clues

Higher twist ratio in Cat 5 , at-least 12 twists/ foot Cat 3 has 3 twists/foot

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Cat 3 jacket is loose than Cat 5

Cat 5 can support only a small amount of untwistingbefore termination.

Cat 5 provides better throughput. 1/23/2013Sumati J. Singh


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STP and UTP Cost STP is generally more expensive and also requires grounding

and installation charges. UTP 6 is costly too.

Throughput Ranges from 10 to 1000 Mbps depending on type ofwire.

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Connector Both use RJ-45 and RJ-11 connectors

Noise immunity STP is more resistant than UTP UTP may use filtering and balancing to offset the effects of noise

Size & Scalability Max segment length is 100 m or 328 ft. OnEthernet support 1 Mbps to 10 Gbps with max 1024 nodes.



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UTP Performance16



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1/23/201317 Sumati J. Singh


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Terminating Twisted Pair18

Cross over cable1/23/2013Sumati J. Singh


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Coaxial Cable Also called coax

Single core (copper wire) enclosed in insulating sheath,encased in outer conductor metal foil / braid /

combination.

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This outer wrap is used to shield and acts second conductorfor ground

Outer conductor is insulated

Covered in plastic sheath

Insulator is PVC/Teflon 1/23/2013Sumati J. Singh


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Coaxial Cable20



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Characteristic High resistance to noise

Carry signals to larger distances than twisted pair More expensive

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STANDARDS Radio Guide Used to guide radio frequencies in broadband

Different types provide different impedance,

attenuation and throughput Size of core is in AWG ( American Wire Gauge ). High

AWG smaller the diameter



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RG - 6 Impedance of 75 ohms

contains an 18 AWG conducting core.

to deliver broadband cable Internet service and

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over long distances



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RG - 8 50-ohm impedance

10 AWG core.

the medium for the first Ethernet networks

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o owe e ase- s an ar

10 max throughput 10 Mbps

baseband transmission

maximum segment length of 500 meters. known as Thicknet



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RG - 58 50-ohm impedance

24 AWG core

Popular Ethernet network medium in 80s

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ma er ame er an - , more ex e, easy o

install & handle

10Base-2

Thinner than RG-8, also called Thinnet



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RG-59 75 ohm impedance

20 or 22 AWG core

Made of braided copper

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ess expns ve, u grea er a enua on

Used for short connections

RG-6 and RG-59 are commonly used



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Connector F-type

Attach in a way so that the pin in the center of theconnector is the conducting core of the cable

Compressed to attach to cable, connectors are

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threaded and screw together like a nut and boltassembly

Mostly used for RG-6



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Connector BNC (Bayonet Neill-Concelman)

Crimped, compressed and twisted on cable Connects to another BNC via turning & locking

Do not use core of coax have their own conductin in

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Used with RG 59 commonly



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Applications Analog telephone networks

Single cable carries 10000 voice signals

Later used in digital data, carry upto 600 Mbps

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Refraction29



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Critical Angle30



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Reflection31



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Fiber Optic Cable Glass fibers at the core

Covered by glass or plastic cladding Cladding should be of different density as of core

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opaque, prevent light from escaping

Strands of Kevlar (polymeric fiber) surrounds

Plastic sheath



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Fiber Modes33



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SMF Narrow core ( less than 10 microns)

Highly focused, expensive Limits beam to smaller range of angles, close to

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Lower density material , critical angle close enough

to 90 degree

Propagation almost horizontal

Delays are negligible

Allows high bandwidth & longest distances (of all

media) 1/23/2013Sumati J. Singh


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SMF35



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MMF Multiple beams travel

Larger diameter 50 to 115 microns Used as backbone like router to switch /server

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eams rave a eren ang es rom source o

destination

Short distances



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Step Index37



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Graded Index38



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Benefits of Fiber More Reliable

Extremely high throughput Very high resistance to noise

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xce en secur y

Ability to carry signals to larger distances



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Disadvantage Expensive

CablesNICs

Connectors

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hubs

Special equipment to splice

Skilled labor

Connecting two fibers is specialized task

Repairing time is difficult in limited time/resources



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Connectors 10 different types are available

4 are commonly used ST (straight tip)

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LC (local connector)

MT-RJ (mechanical transfer registered jack)

Existing networks generally use SC & ST

With latest technology, LC and MT_RJ are used



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Connectors

LC & MT-RJ are smaller and allow higher density of

connections

-

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multimode fiber in single ferrule ( a short tubewithin, that encircles the fiber to properly align )

Two strands provide for duplex signaling



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Connectors43

STSC


LC

MT-RJ

Topic 7 - Guided Transmission Media.pdf

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