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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…?
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