11

Transmission MediaTransmission Media

22

Transmission MediaTransmission Media

BackgroundBackground Guided MediaGuided Media Unguided MediaUnguided Media

33

Transmission MediaTransmission Media

Power, voice

Radio communication Radio, microwave, satellite

Infrared light

Ultraviolet light

X. Gamma, cosmic rays

Visible light, 430-750 THz

0 3KHz 300 GHz

Electromagnetic Spectrum

44

Transmission Media : Transmission Media : BackgroundBackground

Communication signals are Communication signals are transmitted from one device to transmitted from one device to another in the form of electromagnetic another in the form of electromagnetic energyenergy

They can travel through a vacuum, air They can travel through a vacuum, air or or other transmission mediaother transmission media

Transmission media are divided into Transmission media are divided into two categoriestwo categories– Guided Guided – unguidedunguided

55

Guided MediaGuided Media

Guided Media

Coaxial cable

Twisted pair cable

Fiber-optic cable

Unshielded Twisted pair

Shielded Twisted pair

66

Twisted-Pair Cable

Frequency Range for Twisted-pair cable

77

Unshielded Twisted Pair Unshielded Twisted Pair (UTP) Cable(UTP) Cable

Common type of telecommunication Common type of telecommunication medium in use todaymedium in use today

Its frequency range is suitable for Its frequency range is suitable for transmitting both data and voicetransmitting both data and voice

CheapCheap Flexible and easy to installFlexible and easy to install

88

UTPUTP

99

UTP CategoriesUTP Categories

5 EIA categories (CAT1-5)5 EIA categories (CAT1-5) 1 1 lowest quality, 5 lowest quality, 5 highest quality highest quality CAT1CAT1

– Basic twisted pair, used in telephone Basic twisted pair, used in telephone systemsystem

– Quality is fine for voiceQuality is fine for voice Not enough for data communicationNot enough for data communication (Low speed)(Low speed)

1010

UTP CategoriesUTP Categories

CAT2CAT2– Suitable for voice and data communicationSuitable for voice and data communication– Speed is up to 4 MbpsSpeed is up to 4 Mbps

CAT3CAT3– Required to have at least 3 twist per footRequired to have at least 3 twist per foot– Some other requirementsSome other requirements– Transmission rate Transmission rate up to 10 Mbps up to 10 Mbps

CAT4CAT4– Similar requirement as CAT3Similar requirement as CAT3– Transmission rate Transmission rate up to 16 Mbps up to 16 Mbps

CAT5CAT5– Transmission rate Transmission rate up to 100 Mbps up to 100 Mbps

1111

UTP ConnectorUTP Connector

The most frequently used is an RJ45The most frequently used is an RJ45

1212

Shielded Twisted PairShielded Twisted Pair (STP)(STP)

1313

Coaxial CableCoaxial Cable

1414

Optical FiberOptical Fiber

Glass/plasticGlass/plastic Transmits signal in form of lightTransmits signal in form of light Nature of lightNature of light

– Fastest speed Fastest speed in vacuum in vacuum 300,000 km/sec300,000 km/sec

– RefractionRefraction

1515

Optical FiberOptical Fiber

Optical fiber uses Optical fiber uses reflectionreflection to guide to guide light through a channellight through a channel

A glass or a plastic core is surrounded A glass or a plastic core is surrounded by a cladding of less dense glass or by a cladding of less dense glass or plasticplastic

Information is encoded onto a beam of Information is encoded onto a beam of light as a series of on-off flashes that light as a series of on-off flashes that represents 1 and 0 bitsrepresents 1 and 0 bits

1616

Propagation ModesPropagation Modes

Current technology supports two form Current technology supports two form for propagating light along optical for propagating light along optical channelchannel– MultimodeMultimode– Single modeSingle mode

MultimodeMultimode– Multiple beams move through the core in Multiple beams move through the core in

different pathsdifferent paths Single ModeSingle Mode

1717

MultimodeMultimode

Multimode Graded-IndexMultimode Step-Index

1818

Single ModeSingle Mode

1919

Fiber Construction

2020

Fiber SizesFiber Sizes

Defined by the ratio Defined by the ratio of diameter of the of diameter of the core to the diameter core to the diameter of the cladding of the cladding (micrometers) (micrometers)

Common sizes areCommon sizes are

Fiber TypeFiber Type Core Core (microns)(microns)

Cladding Cladding (microns)(microns)

62.5/12.562.5/12.5 62.562.5 12.512.5

50/12.550/12.5 5050 12.512.5

100/140100/140 100100 140140

8.3/12.58.3/12.5 8.38.3 12.512.5

2121

Fiber Optic Advantages Fiber Optic Advantages

Noise resistanceNoise resistance– Noise is not a factor to lightNoise is not a factor to light– External light is blocked from the channel External light is blocked from the channel

by the outer jacketby the outer jacket Less signal attenuationLess signal attenuation

– Transmission distance is greater than Transmission distance is greater than other mediaother media

– A signal can run for a long distance A signal can run for a long distance without requiring regenerationwithout requiring regeneration

2222

Fiber Optic AdvantagesFiber Optic Advantages

Higher BandwidthHigher Bandwidth– Supports higher bandwidth than other Supports higher bandwidth than other

mediamedia– Data rate is also highData rate is also high– The limitation of data rate and bandwidth The limitation of data rate and bandwidth

depends on the signal generation and depends on the signal generation and reception technologyreception technology

2323

Fiber Optic DisadvantagesFiber Optic Disadvantages

CostCost Installation/MaintenanceInstallation/Maintenance FragilityFragility