3.2 Transmission medium: classification based on electromagnetic wave spectrum 3.3 Guided Media -Twisted pair (UTP,STP) cable -connector, Coaxial cable - connector, Fibcr-optic cable - connector, performance and applications 3.4 Unguided Media-Radio waves, microwaves, Infrared and their applications

1. Physical Layer:
Transmission Medium
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2. Transmission Media
Transmission medium:: the physical path between
transmitter and receiver.
• Repeaters or amplifiers may be used to extend the length
of the medium.
• Communication of electromagnetic waves is guided or
unguided.
❑ Guided media: Waves are guided along a physical path
(e.g, twisted pair, coaxial cable and optical fiber)
❑ Unguided media: Media Meant for transmitting but not
guiding electromagnetic waves (e.g., the atmosphere and
outer space).
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3. Transmission Media Choices
• Twisted pair
• Coaxial cable
• Optical fiber
• Wireless communications
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4. Types of Transmission Media
Transmission Media
Guided Media Unguided Media
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5. Figure Transmission medium and physical layer
Transmission medium and physical layer
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6. Figure Classes of transmission media
Classes of Transmission Media
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7. GUIDED MEDIA
Guided media, which are those that provide a conduit from
one device to another, include twisted-pair cable, coaxial
cable, and fiber-optic cable.
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8. Guided Media
 Guided media are the physical links through which signals
are confined to narrow path. These are also called guide
media. Bounded media are made up o a external conductor
(Usually Copper) bounded by jacket material. Bounded
media are great for LABS because they offer high speed,
good security and low cast. However, some time they cannot
be used due distance communication. Three common types
of bounded media are used of the data transmission. These
are
 Coaxial Cable
 Twisted Pairs Cable
 Fiber Optics Cable
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9. Twisted Pair
• Two insulated wires arranged in a spiral pattern
• Copper or steel coated with copper
• The signal is transmitted through one wire and a ground
reference is transmitted in the other wire.
• Typically twisted pair is installed in building telephone
wiring.
• Local loop connection to central telephone exchange is
twisted pair.
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10. Twisted Pair
• Limited in distance, bandwidth and data rate due to
problems with attenuation, interference and noise
• Issue: cross-talk due to interference from other signals
• “shielding” wire (shielded twisted pair (STP)) with
metallic braid or sheathing reduces interference.
• “twisting” reduces low-frequency interference and
crosstalk.
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11. Shielded twisted pair (STP) an d Unshielded
twisted pair (UTP)
• Cables with the shield are called shielded twisted pair and
commonly abbreviated STP.
• Cables without a shield are called unshielded twisted pair or
UTP.
• Twisting the wires together results in characteristics
impedance for the cable.
• UTP or unshielded twisted pair cable is used on Ethernet
• UTP cables are used for Ethernet cabling where 4 twisted
pair cables (a total of 8 wires are used)
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12. Unshielded twisted pair (UTP)
Cables with the shield are called shielded twisted pair and
commonly abbreviated STP.
Cables without a shield are called unshielded twisted pair or
UTP.
Twisting the wires together results in characteristics
impedance for the cable.
UTP or unshielded twisted pair cable is used on Ethernet
UTP cables are used for Ethernet cabling where 4 twisted pair
cables (a total of 8 wires are used)
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13. Shielded twisted pair (STP)
It is similar to UTP but has a mesh shielding that’s protects
it from EMI which allows for higher transmission rate.
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Unshielded twisted pair (UTP)
UTP is more common. It can be either voice grade or data
grade depending on the condition. UTP cable normally has
an impedance of 100 ohm. UTP cost less than STP and
easily available due to its many use. There are five levels
of data cabling.

14. Figure Twisted-pair cable
Twisted-Pair cable
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15. Figure UTP and STP cables
UTP and STP cables
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16. Shielded twisted pair (STP) and UTP Cable (Non
Shielded)
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17. Shielded twisted pair (STP) and UTP Cable (Non
Shielded)
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18. Figure UTP connector
UTP connector
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19. Figure Coaxial cable
Coaxial Cable
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20. Center
conductor
Dielectric
material
Braided
outer
conductor
Outer
cover
Copyright ©2000 The McGraw Hill Companies
Coaxial Cable
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21. Coaxial Cable
• Discussion divided into two basic categories for coax
used in LANs:
• 50-ohm cable [baseband]
• 75-ohm cable [broadband or single channel baseband]
• In general, coax has better noise immunity for higher
frequencies than twisted pair.
• Coaxial cable provides much higher bandwidth than
twisted pair.
• However, cable is ‘bulky’.
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22. Coaxial Cable
• Coaxial cable consists of 2 conductors. • The inner
conductor is contained inside the insulator with the other
conductor weaves around it providing a shield. • An
insulating protective coating called a jacket covers the outer
conductor.
• The outer shield protects the inner conductor from outside
electrical signals.
• The distance between the outer conductor (Shield) and inner
conductor plus the type of material used for insulating the
inner conductor determine the cable properties or
impedance. The excellent control of the impedance
characteristics of the cable allow higher data rates to be
transferred than twisted pair cable.
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23. Coaxial cable
 Coaxial cable is very common & widely used commutation media. For
example TV wire is usually coaxial. Coaxial cable gets its name because
it contains two conductors that are parallel to each other. The center
conductor in the cable is usually copper. The copper can be either a solid
wire or stranded martial.
 Outside this central Conductor is a non-conductive material. It is
usually white, plastic material used to separate the inner Conductor
form the outer Conductor. The other Conductor is a fine mesh made
from Copper.
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24. Optical Fiber
• Optical fiber: A thin flexible medium capable of conducting
optical rays. Optical fiber consists of a very fine cylinder of
glass (core) surrounded by concentric layers of glass
(cladding).
• A signal-encoded beam of light (a fluctuating beam) is
transmitted by total internal reflection.
• Total internal reflection occurs in the core because it has a
higher optical density (index of refraction) than the
cladding.
• Attenuation in the fiber can be kept low by controlling the
impurities in the glass.
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25. Optical Fiber
• Optical fiber consists of thin glass fiber that can carry
information at frequencies in the visible light spectrum. • The
typical optical fiber consists of a very narrow strand of glass
called the cladding.
• A typical core diameter is 62.5 microns. Typically cladding
has a diameter of 125 minors. Coating the cladding is a
protective coating consisting of plastic, it is called the jacket.
• The device generating the message has it in electromagnetic
form (electrical signal); this has to be converted into light (i.e.
optical signal) to send it on optic fiber cable. The process of
converting light to electric signal is done on the receiving
side.
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26. Fiber optic cable
 Fiber optic cable uses electrical signals to transmit
data. It uses light. In fiber optic cable light only
moves in one direction for two way communication
to take place a second connection must be made
between the two devices. It is actually two stands of
cable. Each stand is responsible for one direction of
communication. A laser at one device sends pulse of
light through this cable to other device. These pulses
translated into “1’s” and “0’s” at the other end.
 In the center of fiber cable is a glass stand or core.
The light from the laser moves through this glass to
the other device around the internal core is a
reflective material known asCLADDING. No light
escapes the glass core because of this reflective
cladding.
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27. core
cladding jacket
light
c
(a) Geometry of optical fiber
(b) Reflection in optical fiber
Optical Fiber
Leon-Garcia & Widjaja: Communication Networks
Copyright ©2000 The McGraw Hill Companies
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28. Figure: Optical fiber
Optical fiber
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29. Figure: Fiber optics: Bending of light ray
Fiber optics: Bending of light ray
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30. Figure : Fiber construction
Fiber construction
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31. Figure : Fiber-optic cable connectors
Fiber-optic cable connectors
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32. Figure Propagation modes
Propagation Modes
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33. Figure Modes
Modes of Propogation
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34. Fiber types
Fiber Types
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35. UNGUIDED MEDIA: WIRELESS
Unguided media transport electromagnetic waves without using a
physical conductor. This type of communication is often referred to
as wireless communication.
Radio Waves
Microwaves
Infrared
Topics discussed in this section:
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36. Unguided Media
• Unguided media or wireless media doesn't use any physical connectors
between the two devices communicating. Usually the transmission is
send through the atmosphere but, sometime it can be just across the
rule. Wireless media is used when a physical obstruction or distance
blocks are used with normal cable media. The three types of wireless
media are:
 Radio waves
 Micro waves
 Infrared waves
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37. Unguided Media
• Unguided media transport data without using a physical
conductor. This type of communication is often referred to
as wireless communication. It uses wireless electromagnetic
signals to send data.
• There are three types of Unguided Media (i) Radio waves (ii)
Micro waves (iii) Infrared.
• These signals can be sent or propagated in the following
three ways:
1. Ground-wave propagation 2. Sky-wave propagation 3.
Line-of-sight propagation
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38. Figure Wireless transmission waves
Wireless transmission waves
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39. Ground-wave Propagation
• In this type of way, the signals are transmitted in the lowest layer of the
atmosphere and can be sent in all directions using the antenna as a
transmitting device. The signals are transmitted as the frequency is lower
for this signal.
• Characteristics of Ground-wave propagation are as follows: i. Follows
contour of the earth ii. Can Propagate considerable distances iii.
Frequencies up to 2 MHz iv. Example a. AM radio
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40. Ground-wave Propagation
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41. Sky Wave Propagation
In this type of way, the signals are transmitted that has usually high-
frequency and can be transmitted using the sky as a medium. In this way, the
radio waves are transmitted in the upward direction and then signals get
reflected because of the ionosphere and reach to earth surface again. By this,
the signals can be transmitted for longer distances consuming less power.
Characteristics of Sky Propagation are as follows:
• i. Signal reflected from ionized layer of atmosphere back down to earth
• ii. Signal can travel a number of hops, back and forth between ionosphere
and earth‘s surface
• iii. Reflection effect caused by refraction iv. Examples a. Amateur radio b.
CB radio
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42. Sky Wave Propagation
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43. Line of Sight Propagation
In this type of way, the signals having a very high frequency is transmitted
using the antenna to antenna communication.
Characteristics
i. Transmitting and receiving antennas must be within line of sight a.
Satellite communication – signal above 30 MHz not reflected by
ionosphere b. Ground communication – antennas within effective line of
site due to refraction
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44. Line of Sight Propogation
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45. Figure : Electromagnetic spectrum for wireless communication
Electromagnetic spectrum for wireless communication
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46. Figure : Propagation methods
Propagation Methods
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47. Figure : Propagation methods
Propagation Methods
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48. Figure : Propagation methods
Propagation Methods
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49. Propagation Methods
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Radio waves application:
1.The radio waves are used where there is a requirement of sending the same
information to multiple users from a single source.
2.The applications of radio waves are television, FM radio, and cordless
phone.
Microwave application:
1.The unicast transmission becomes easier using microwave transmission.
2.The microwaves are used in satellite network communication and wireless
LANs.

50. Propagation Methods
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Infrared application:
1.The data transmission quality for the infrared is comparatively higher than
other types of electromagnetic waves.
2.Used in computer system components to have communication between
them.

51. Advantages of Unguided Media Transmission
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There are several advantages of unguided media transmission.
1. The bandwidth of unguided media transmission is higher when it is
compared to guided transmission media. The information can be shared
without having any disturbance from any medium.
2. The unguided transmission media does not get affected by corrosive
materials as there is no direct communication between the sender node and
the destination node.
3. The price of unguided media transmission is lower compared to guided
transmission media as there are no physical cables or wires used which help
to reduce the setup cost for the unguided transmission medium.

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4. A single time, the same information can be broadcast to multiple users
without having any delay. For example, broadcast of radio or tv channels in
which multiple users can use the device for getting information.
5. The signals in unguided transmission media can be transmitted for long
distances without having any disturbance from medium and without
compromising quality.
6. The signal attenuation is lower in the unguided transmission medium. As
there is no physical wire or cable used the attenuation is lower in
information transmission.
Advantages of Unguided Media Transmission

53. Figure : Propagation methods
Propagation Methods
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54. Figure : Propagation methods
Propagation Methods
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55. Figure : Propagation methods
Propagation Methods
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56. Table Bands
Bands
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57. Thank You