Transmission Media…

Asad Ullah Reg No: 07MDTLC0295 Faiz Ullah Reg No: 07MDTLC0293

Contents

Transmission Media & Types. Unguided Transmission Media ( Radio Waves, Microwaves, Infra red Waves ) & Applications.

Guided Media1) Optical Fiber, Applications, Advantages & Disadvantages.2) Co-axial Cable3) Twisted Pair Cable 4) Waveguides Comparison of Different guided Medias. References

Transmission Media The Medium or path in which the communication between transmitter and receiver

takes place is known as Transmission Media. Transmission Media can be classified in two types… Unguided and guided medias.

Transmission Media

Unguided Transmission Media(Wireless Media)

Guided Transmission Media(Wired Media)

Air and Space(MicrowavesSatellite links

Infra red waves)Optical Fiber Cable Co-axial Cable Twisted Pair Cable

Waveguides

Electromagnetic Wave Spectrum

0 102 104 106 108 1010 1012 1014 1016 1018 1020 1022

Long wave

Standard

broadcast VHF

UHFShort wave

Radiofrequencies

Microwave

Millimeter

Wave

Far infrared

infrared

Ultraviolet

X-Rays

Gamma Rays

Cosmic rays

Red

~0.7 µm

Violet

~0.4 µm

1.7 µm 0.8 µm

Optical Fiber Communication

Frequency (Hz)

Wavelength3000 km 30 km 300 m 3 m 3 cm 0.3 mm 3 µm 30 nm 0.3 nm 3 pm 0.3 pm

f = 1/T λ = c/f c = 3x108 m/s

Unguided Transmission Media

Also known as Wireless Media. Use Electromagnetic Waves of different frequencies and do not need a wire or cable

conductor to transmit signals. No physical connection between transmitter and receiver. Radio Waves Microwaves Infra red Waves

Applications of Unguided Media Radio Waves:

Radio waves are used for Multicast communications ,such as radio and television, and paging systems.

Microwaves:

Microwaves are used for unicast communication such as cellular telephones, satellite networks, and

wireless LANs.

Infra red Waves:

Infrared signals can be used for short-range communication in a closed area using line-of-sight propagation.

Advantages of Unguided Media

Very useful in difficult terrain where cable laying is not possible.

Provides mobility to communication nodes.

Right of way and cable laying costs can be reduced.

Susceptible to rain, atmospheric variations and Objects in transmission path. Frequency Limitation Losses Interference Fading

Disadvantages of Unguided MediaDisadvantages of Unguided Media

Guided Transmission Media

Also known as conducted media. Use a conductor such as a wire or a fiber optic cable to move the signal from sender to

receiver. Guided Media have different types major are… Optical Fiber Cable Twisted Pair Cable Co-axial Cable Waveguides

Optical Fiber…

Optical Fiber is a thin strand of highly transparent glass or sometimes plastic that guide light. It is used as a medium for carrying information from one point to another in the form of light.

Dielectric Wave guide

A basic Optical Fiber system consists of… Transmitting device Optical fibre cable Optical Regenerator Receiver The fibre itself is passive and does not contain any active properties

ElectricalSignal Input

Light Source (Transmitter)

Optical Fiber Cable

Light DetectorReceiver

ElectricalSignal output

Optical Fiber Construction…

Core: The centre of the fibre through which the light is transmitted.

Cladding: The outside optical layer of the fibre that traps the light in the core and

guides it along and even through curves. Jacket: Used for protecting the inner materials from damaging.

Core

Cladding JacketLight

Principle of Operation

Total internal reflection Refractive index of core is greater than that of cladding. Angle of incidence should be greater than Critical angle ϴc

Numerical Aperture

c

Types of Optical Fiber Cables…

Light waves follows only one path…

Types Of

Optical Fiber

Mode wise types Index wise types

Single Mode(Single Path)

Multi Mode(Multi Path)

Step Index Graded Index

Core (dia) = 50 micronsCladding (dia) = 125 microns

Core (dia) = 62.5 micronsCladding (dia) = 125 microns

Core (dia) = 8.3 micronsCladding (dia) = 125 microns

Light follow a lot of reflecting paths to go from txr to rxr…

Have only one core and cladding of fix refractive index values…

From

the central axis to the outer side each point act as low

refractive index media by

which the light follow

s sine path…

Fibre Optic Splicing…

Two methods of fibre optic splicing…

Mechanical Splicing: To hold the two fibres ends in a precisely

aligned position

(Typical loss: 0.3 dB)

Fusion Splicing: The joining and fusing of two fibres by

placing them between two electrodes, and discharging an electric arc over the fibres.

Lower loss and less back reflection than

mechanical splicing. (Typical loss: 0.1 dB)

Stripping of fibres

Once the coated fibre is exposed, Use fibre stripper to strip fibre to appropriate length. Take care not to damage the fibres in the process.

Cleaning After the coating is removed, clean the fibre with specially designed isopropyl alcohol wipes so that the fibre squeaks.

Cleaving A good cleave is the key to obtaining a good splice. Use cleaver to cut the fibre. After cleaving do not touch or clean the fibre.

Splicing The fibre is now ready to be spliced mechanically or Fusion. Insert the fibre carefully in the mechanical splice or in the fusion splicer for splicing. While inserting in the mechanical splice make sure that fibre is inserted directly in the groove and do not touch any other surface. Fusion splicer will automatically align and fuse the fibre.

Protection In case of fusion splicing cover the splice with heat shrink sleeve and place it in the heater, for mechanical splice carefully close the mechanical splice.

Organizing Organize the fibre in the enclosure properly Make sure that organising do not cause Micro-bending.

Applications of Optical Fiber Public and Private Telecommunication Lines.

Computer networks (LAN, WAN ).

Television distribution network.

Military network.

Control, remote control and Signalizing network.

Video supervision lines.

CCTV- closed-circuit TV.

Optical Fiber Sensors.

Local/ Junction Network.

Fiber Access Network.

Submarine Network.

Free Space Optics (FSO).

Medical Services.

Angiography.

Advantages Of Optical Fiber Non Conductivity / No Short circuit Wide Temperature Range Material Availability Security Large / Wide Bandwidth: Suitable for high speed.wide-band,large-capacity telecommunication lines

Low Loss: Because of low loss, few or no amplifiers are necessary.

Very Light Weight: The smallest cables can be designed and manufactured, therefore reduce pulling strength and reduce

Laying cost.

Economic: The most economical solution for the simultaneous transmission of servile multi channel users.

No cross Talk Being non-inductive there is no induction of signal into/from other circuits so that possibility of cross talk is

virtually eliminated.

Many channel Capacity Many wavelengths can be used.

Small size Freedom from interference No corrosion

Disadvantages Of Optical Fiber

Cost

Although availability of raw material is guaranteed, the manufacture of Optical Fiber extremely difficult and involves complete set up for heat and chemical treatment of sio2 to reach the

desired purity required to producing Optical Fibre. Remote Power Feeding

Power of operation of regenerators cannot be transmitted on Optical Fibre (Dielectric nature). Additional arrangements are to be made for this purpose e.g. use of stand by batteries, solar power panels etc.

Mechanical Problems. Non-Linear characteristics of Optical converters

The electrical and optical characteristics of optical converters are non-linear, which results in extra noise, loss of power, coupling efficiency of optical sources, conversion efficiency of optical devices etc.

Hazards with lasers Limited bend radius Difficult to splice / Alignment Problems Hard Installation

Co-axial Cable Mainly designed for minimizing radiation losses. Composed of an inner conductor carrying the signal with grounded outer braided

conductor. Both conductors share a common center axial, hence the term “co-axial”

• Inner Conductor: An aluminum or copper conductor.

• Insulator: A dielectric material (Polystyrene, Pyrex)

• Plastic Cover: A polyethylene outer jacket.

Co-axial cable performance Categories of Co-axial cable over different frequencies…

Category Impedance Use

RG-59 75 Ω Cable TV

RG-58 50 Ω Thin Ethernet

RG-11 50 Ω Thick Ethernet

35

30

10

25

20

5

15

Atte

nua

tion

(dB

/km

)

0.1 1.0 10 100f (MHz)

2.6/9.5 mm

1.2/4.4 mm

0.7/2.9 mm

Twisted Pair Cable Two insulated copper

wires arranged in a regular spiral pattern to minimize interference

Various thicknesses, e.g. 0.016 inch (24 gauge)

Twisted pairs can provide high bit rates at short distances.

Att

enua

tion

(dB

/mi)

f (kHz)

19 gauge

22 gauge

24 gauge26 gauge

6

12

18

24

30

110 100 1000

Types of Twisted Pair Cable

Unshielded Twisted Pair Cable Shielded Twisted Pair Cable

Categories of Twisted Pair Cable

Category Description Data Rate (Mbps)

CAT-1 Unshielded Twisted Pair used for Telephone. <0.1

CAT-2 Unshielded Twisted Pair used for T1 data. 2

CAT-3 Improved CAT-2 used for computer networks. 10

CAT-4 Improved CAT-3 used for Token Ring networks. 20

CAT-5CAT-5E

Unshielded Twisted Pair used for networks.Extended CAT-5 for more noise immunity.

100-125

CAT-6 Unshielded twisted pair used in computer networks for high data rates.

200

CAT-7 Shielded Twisted Pair with foil shield around the entire cable plus a shield around each twisted pair.

600

Waveguides

Skin effect in other Metallic Medias. At high frequencies we use waveguides as a transmission media. Hollow metal structure Strip lines Mostly used as antenna feeder Rectangular, Circular and Conical waveguides No Radiation loss Less attenuation High Power Capacity.

Applications of Waveguides Microwave Oven Coupling Feeder Radar PCB Medical Ultrasonography Medical Stethoscope etc etc…

Comparison of guided medias discussed…

Cables

References

www.wikipedia.com www.britannica.com Data communications & Computer Networks by Behrouz Farozan. www.pptsearch.com www.ptcl.com.pk Alyaan Communications, Mardan. www.TheFOA.org Modern Electronic Communication by Miller & Beasley.

Any Question…?