various types of transmission media

2.  It is a pathway that
carries the information
from sender to receiver.
 Different types of cables
or waves are used to
transmit data.
 Data is transmitted through:-
ELECTRICAL
SIGNAL
-It is in the form
of current.
ELECTROMAGNETIC
SIGNAL
-It is is eries of
electromagnetic energy
pulses at various frequencies.

3.  TRANSMISSION CAPABILITIES depends upon
 BANDWIDTH
-data carrying capacity of medium or channel.
higher bandwidth, higher data rates
 RADIATION
-leakage of signal from the medium due to undesirable
characteristics of the medium.
 NOISE ABSORPTION
-the susceptibility of the media to external electrical noise
that can cause distortion of data signal.
 ATTENUATION
-loss of energy as signal propagates outward. The amount
of energy lost depends on frequency.

4. TYPES OF TRANSMISSION
MEDIA
MAGNETIC
• DVD
GUIDED/
WIRED
• CO-AXIAL
CABLE
• FIBRE OPTICS
• TWISTED
PAIRS
UNGUIDED/
WIRED
• RADIO
• MICROWAVE
• INFRARED
• LIGHT WAVE
TYPES

5. MAGNETICMEDIA
 It is one of the way to transport data from one computer to another
by writing it on magnetic tape or removable media and physically
transporting the tape to the destination machine and read them
again.
 Example:
 DVD has capacity in tera bytes.
 Advantages:
 It is more cost effective, for application in which high bandwidth or
cost per bit transported is the key feature.

6.  It consists of THIN GLASS FIBRES or plastic that can
carry information at frequencies in the visible light
spectrum and beyond.
 The typical optical fiber consists of a very narrow
strand of glass called the core(62.5 microns). Around
the core is a concentric layer of glass called
CLADDING(125microns). coating of cladding is protective
consists of plastic(jacket).

7. OPTICAL FIBRE COMPONENTS
COMPONENTS
LIGHT SOURCE
-1(absence of light)
-0(pulse of light)
-can be an LED or a laser beam
TRANSMISSION
MEDIUM
-ultra thin fiber of
glass
DETECTOR
-generates an
electrical pulse when
the lights falls on it.

8. REFRACTION
 Light ray passes from one medium to
another, the ray is refracted at the
boundary at an angle α1 and emerging at an
angle β1.
 The amount of refraction depends upon the
properties of two medium.
 For an angle of incidence above a critical
value, the light is refracted back into the
medium. None of its escapes into the air.

9. TYPES OF OPTICAL FIBRES

10. TYPES OF FIBERS
 SINGLE MODE FIBRE:
 Diameter::8 to 10 microns
 Light can propagate only in straight line without bouncing.
 Critical angle close enough to 90 degree such that beam propagates in a
straight line.
 These are expensive and are widely used for long distance
communication.
 Can transmit data at 50 gbps for 100 kilometers without amplification.
 MULTIMODE FIBRE:
 Multiple beams travel in the core in different paths.
 Diameter:50 microns

11. MULTIMODE FIBRE STEP INDEX FIBRE:
 Density of core remains constant from the centre to the edges.
 A beam of light moves in a straight line in this medium until it reaches the
interface of core and cladding.
 At this intterface,the angle of ray is changed due to the change in density.
 In this mode,some beams travel in the straight line through the core and
reaches destination without reflection or refraction.
 The beams that strike the interface of core and cladding at and angle
smaller than critical angle penetrate the cladding and are lost.
 The beams striking at angle greater than critical angle are reflected back
in core and forms total internal reflection.
 GRADED INDEX FIBRE
 It has different densities at the core and at the edge.
 Because of this difference in densities different beams refract at different
angles into a curve.
 Only the horizontal beams move in a straight line due to constant density
at the center

12. ADVANTAGES OF OPTICAL FIBRES
 Not affected by electrical and magnetic interference as the data travel in for of light.
 higher bandwidth
 Thin, lighter , small in size
 Can easily be grouped in one bundle.
 Glass can be laid in different environments.
 Attenuationis very low. Attenuation =10 log 10 transmitted power/receieved power.
It is measured in decibels.
 Provide Security against wire tappers as they do not leak light
 No cross-talk problem.
 Lower cost as material used in them silica glass is easily available.
 Information carrying capacity is much higher.
 Transmission rate:45 mb/s to 9.6 gb/s

13. DISADVANTAGES OF OPTICAL
FIBER
 Fragile
More easily broken than wires.
Need to be put deep into land. Causes lot of installation cost.
Being new in technology require skilled people
for administration and maintenance
Optical fibers are unidirectional for two –way
communication, two fibers are required.

14. APPLICATION OF OPTICAL FIBER
In the local area networks.
In telephone lines.
In backbone of networks.

15. CO-AXIAL CABLES
 Known as “COAX”
 Two kinds of co-axial cables are used.
 50 ohm
 75 ohm
• Used for analog transmission and cable television
• It can span longer distance.
TYPES
BASEBAND
-transmit a signal at a
time at very high speed
-supports frequency range
of 4kHz
-cables are 50 ohms
-can be used with low
data rates or periodic
amplifiers
BROADBAND
-transmit many
simultaneous signals
using different
frequencies
-supports frequency
range above 4kHz
-cables are 75 ohms
-can be used for analog
transmission.

16. STRUCTURE OF
COAXIAL CABLE
 It consists of a stiff copper wire as the core,surronded by an insulating
material.
 This insulator is encased in a conductor, often as a closely –woven braided
mesh.
 the outer conductor is covered in a protective plastic sheath.

17. ADVANTAGES/DISADVANTAGES
 ADVANTAGES:
 Can be used for both analog and digital transmission
 Oofer high bandwidth
 Loss of signal or attenuation is less due to better
shielding
 Also offers good noise immunity
 Inexpensive as compared to optical fiber
 Lower error rates compared to twisted pair
 Not easy to tap because copper wire is contained in
plastic jacket
 DISADVANTAGES:
 High installation cost
 High maintenance cost

18. APPLICATIONS OF
COAXIAL CABLES
Analog telephone networs
Digital telephone networks
Cable tv
Traditional ethernet lans
Digital transmission
Thick ethernet

19. TWISTED PAIRS
 Twisted pair consists of two copper wires about 1mm thick.
 These wires are twisted together in helical form.
 Polyethylene, polyvinyl chloride, four polymer resin and Teflon(r) some of the substances
that are used for insulation purposes.
 Gauge: it is measure of thickness of the conductor. The thicker the wire the less is the
resistance, the stronger the signal over a given distance and the better the performance of the
medium.
 The bandwidth of twisted pair depends on-
 The gauge of the conductor
 Length of the conductor
 Spacing of the amplifiers

20. WHY TWISTING?
 Number of twists per unit length will determine the quality of
cable. More twists means better quality.
 Twisting of wires will reduce the effect of noise or external
interference.
 If the two wires are parallel the the electromagnetic interference from
the devices such as motor can a create a noise .
 Interference on the wire that is closer to the source of the noise this
results in high voltage level in one wire than the other.this further
leads to uneven load and damaged signal and there will difference at
the receiver side.
 If the two wires are twisted ,then the comulative effect of the
interference on both the wires are equal.in one twist one wire is closer
to the noise source and the other is farther,in the next twist the
reverse is true
 In this way , there will be no difference at the reciever side as
unwanted signals are cancelled out.

21.  STP
-SHIELDED TWISTED PAIRS
-made up of copper wires that are
twisted together.
-the pairs are covered in a foil or
braided mesh, as well as outer
PVC jacket.
This foil or mesh prevents the
penetration of em noise and
eliminate cross –talk
-this shielding must be grounded to
prevent the foil or braided mesh
from becomin a magent for
electricity.
TYPES OF
TWISTED
PAIRS
UTP
-UNSHIELDE TWISTED PAIR
-Consists of color-coded copper
wires, but does not include any
foil or braiding
-wire pairs within each cable have
varied amounts of twists per foot
to produce cancellation.
-there are several categories of
UTP.

23. ADVANTAGES OF STP OVER UTP:
STP is less susceptible to noise as compared to UTP
and therefore reduces the cross talk and interference
DISADVANTAGES OF STP:
It must be properly grounded.
It is more expensive than UTP.
It is difficult to terminate

24. ADVANTAGES OF TWISTED
PAIRS
 It can be used to carry both analog and
digital data.
 It is relatively easy to implement and
terminate.
 It is the least expensive media of
transmission for short distances
 If portion of a twisted pair cable is
damaged it does not effect the entire
network.

25. DISADVANTAGES OF TWISTED PAIRS
 It offers poor noise immunity as a result
signal distortion is moroe.
 Attenuation is very high.
 It supports lower bandwidth as compared to
other medias.
 It supports 10 mbps upto a distance of 100
meters.
 It offers poor security and are easily to tap.
 Being thin in size they are likely to break
easily.

26. APLICATION OF TWISTED PAIRS
In telephone lines to carry voice
and data channels.
In the local loop
In the DSL(ADSL)
 in Local area network
In the ISDN

28.  For the users who use
mobile,laptops,notebook,palmtop,wrist-
watch computers coax fibers are of no use
 So, wireless network is introduced

29.  Radio waves are easy to generate,can travel
long distances,and can penetrate buildings
easily
 They are widely used for communication,both
indoors and outdoors.
 Radio waves are omnidirectional
 They travel in all directions from the source.

30.  They are frequency
dependent
 AT LOW FREQUENCY:
 radio waves pass through
obstacles well
 the power falls off sharply with distance from the source,
roughly as 1/r(square) in air
 In VLF,LF and MF bands ,radio waves follows ground, as
 PROBLEM:
 These bands has low bandwidth
 These waves can be detected for thousand kilometers at the
lower frequencies less at the higher ones
 For example: AM radio broadcasting

31.  Radio waves tend to travel in straight lines and bounce off
obstacles.
 They are also absorbed by the rain.
 At all frequencies,
radio waves are subject
to interference from
motors and other electrical
equipments. How ever the
waves that reach the
ionosphere are refracted by it
and send back to the earth
 The military also communicates HF and VHF bands

32. MICROWAVE
TRANSMISSION
 The microwave travels in a straight line if the towers are too far apart
 The earth will get in the way so repeaters are required periodically.
 The higher the towers are the farther apart they can be.
 For 100meter high tower repeaters can be spaced 80 km apart.
 Microwave do not pass through buildings.
 Some waves may be refracted of low line atmospheric layers and may
take slightly longer to arrive out of phase with direct wave and thus
cancel the signal
 This effect is called multipath fading
 Microwave communication is so widely used for long distance,
telephone communication, mobile phones, television.
 They are relatively inexpensive.

33. INFRARED RANGE
 They are widely used for short range communication
 Uses:
 Remote control on television,vcr,sterios
 ADVANTAGES: They are relatively
 Directional
 Cheap
 Easy to built
 Limitation:
 They do not pass through solid objects.

34. LIGHT WAVE TRANSMISSION
The laser's strength has very narrow
beam
It can penetrate rain or thick fog.
It is also responsible for shimmering
roads on a hot day and wavy images
seen when one looks out above a hot
radiator.

35.  REFERENCE
 +2 text book(PSEB)
 COMPUTER NETWORKS(Andrew S.Tanenbaum)
PEARSON(4th edition)
 www.ecomputernotes.com/computernetworkingnotes
/communication-networks/describe-the-different-
transmisssion-media