all about transmission media

1. Transmission Media

2. What is Transmission Media
• Transmission media is a medium through
which data can be transmitted over long
distances.
• A transmission medium is a material
substance (solid, liquid, gas, or plasma) that
can propagate energy waves. For example,
the transmission medium for sounds is
usually air, but solids and liquids may also act
as transmission media for sound.

3. • Data is represented by computers and other
telecommunication devices using signals. Signals
are transmitted in the form of electromagnetic
energy from one device to another.
Electromagnetic signals travel through vacuum,
air or other transmission mediums to travel
between one point to another(from source to
receiver).
• Electromagnetic energy (includes electrical and
magnetic fields) includes power, voice, visible
light, radio waves, ultraviolet light, gamma rays
etc.
• Transmission medium is the means through
which we send our data from one place to
another. The first layer (physical layer) of
Communication Networks OSI Seven layer model

5. Guided Media/Wired
Co-axial Cable:-
Coaxial cables are a type of cable that is used
by cable TV and that is common for data
communications. Taking a a round cross-
section of the cable, one would find a single
center solid wire symmetrically surrounded by
a braided or foil conductor. Between the
center wire and foil is a insulating dielectric.

6. Physical Structure of co-axial cable:-
It consist of two concentric conductors separated
by a dielcetric material.
It consist of stiff copper wire as the core ,
surrounded by an insulating material.
This insulator is encased by a cylindrical
conductor, often as a closely woven braided
mesh. The outer conductor is then covered in a
protective plastic sheath.
It gives good combination if high bandwidth &
excellent noise immunity. Higher data rates are
possible on shorter cables.

8. Application of Co-axial Cable
1) Co-axial cable was widely used in analog
telephone networks where single coaxial
network could carry 10,000 voice signals.
2) Cable TV networks also use coaxial cables.
3) It is used in traditional Ethernet LANS.

9. Connector for coaxial cable
• To connect coaxial cable to device ,we need
coaxial cable connector.
• BNC-Bayone-Neill-Concelman connectors
1)BNC connector- used to connect the end end
of the cable to a device such as TV.
2)BNC-T connector-used in ethernet networks
for branching out cable for connection to a
networkpf devices
3)BNC terminator-Used at end of the cable to
prevent the reflection of the signal.

10. Connectors of Coaxial Cable

11. Twisted Pair Cable
Twisted pair cabling is a type of wiring in which two
conductors of a single circuit are twisted together
for the purposes of canceling out electromagnetic
interference (EMI) from external sources. They
have more noise immunity.
It consist of two insulated copper wires about 1 mm
thick. the wires are twisted together in helical
form to eliminate a lot of noise.
Two types of Twisted Pair Cable:-

14. • Shielded Twisted Pair(STP):-
• STP is similar to UTP but with each pair covered
by an additional copper braid jacket or foil
wrapping. This shielding helps protect the signals
on the cables from external interference.
• STP is more expensive than UTP but has the
benefit of being able to support higher
transmission rates over longer distances.
• STP is used in IBM token ring networks.

15. • Unshielded Twisted Pair:-(UTP)
Unshielded twisted pair is the most common
kind of copper telephone wiring. Twisted pair
is the ordinary copper wire that connects
home and many business computers to the
telephone company. To reduce crosstalk or
electromagnetic induction between pairs of
wires, two insulated copper wires are twisted
around each other.

16.  Why to twist the wires?
1)Twisting of wires will reduce the effect of noise or external
interference.
2)Number of twists per unit length will determine the quality
of cable. More twists means better quality.
 Connectors for Twisted pair Cable:-
UTP connector is RJ45 where RJ (Registered Jack)

17. Applications of Twisted Pair cable
• Transmission media for digital and analog
signals.
• It is used in telephone lines to provide voice
and data channels.
• LAN also uses twisted pair cable.
• To connect subscriber to the central telephone
office is mostly UTP channel.

18. Fiber Optics Cable
• A fiber optic cable consists of a bundle of
glass threads, each of which is capable of
transmitting messages modulated onto light
waves. Fiber optics has several advantages
over traditional metal communications
lines: Fiber optic cables have a much greater
bandwidth than metal cables.

19. Fiber Optic Cable Connector

21. Characteristics of fiber optics
• High bandwidth therefore can operate at higher
data rates.
• Reduce losses as the signal attenuation is low.
• Distortion is reduced hence better quality is
assured.
• Small size and light weight.
• Used for point to point communication.

22. Application
1. It is found in backbone networks because its
wide bandwidth is cost effective.
2. Some cable companies use a combination of
optical fiber &coaxial cable.
3. Telephone companies also using optical fiber
Cable.
4. Local Area Network such as 100 Base FX
network use fiber optic cable.

23. • Advantages:-
1. Higher bandwidth
2. Less signal attenuation
3. Noise resistance.
4. Light weight.
5. More security is provided
6. Reliability is more than other &long life span
• Disadvantages:-
1. Installation and maintenance need expertise
2. Propagation of light is unidirectional
3. Fiber optic is more expensive

24. • Unguided media relates
to transmission through the air and is
commonly referred to as wireless. The
transmission and reception of data is carried
out using antenna. There are two main ways
that antenna work: Directional (in a beam)

25. • ELECTROMAGNETIC ENERGY
The electromagnetic spectrum is the range of all possible
frequencies of electromagnetic radiation.
• When you tune your radio, watch TV, send a text
message, or pop popcorn in a microwave oven, you are
using electromagnetic energy. You depend on this energy
every hour of every day. Without it, the world you know
could not exist.
• Electromagnetic energy travels in waves and spans a
broad spectrum from very long radio waves to very short
gamma rays. The human eye can only detect only a small
portion of this spectrum called visible light. A radio
detects a different portion of the spectrum, and an x-ray
machine uses yet another portion. NASA's scientific
instruments use the full range of the electromagnetic
spectrum to study the Earth, the solar system, and the
universe beyond.

28. Wireless Transmission
Radio Waves Infra-Red Micro-Wave

29. Radio Waves:-
Radio waves are a type of electromagnetic radiation with
wavelengths in the electromagnetic spectrum longer than
infrared light. Radio waves have frequencies from 10KHz and
1GHz corresponding wavelengths ranging from 1 millimeter
(0.039 in) to 100 kilometers (62 mi). The best-known use of radio
waves is for communication; television, cell phones and radios
all receive radio waves and convert them to mechanical
vibrations in the speaker to create sound waves that can be
heard.
Radio Waves includes the following types:-
Short waves used in AM radio
Very high frequency(VHF)used in FM radio and TV
Ultra high frequency(UHF)used in TV

31. • Microwave transmission is the transmission of information
or energy by electromagnetic waves whose wavelengths are
measured in small numbers of centimeter; these are called
microwaves. This part of the radio spectrum ranges across
frequencies of roughly 1.0 gigahertz (GHz) to 300 GHz.
Microwave transmission is the transmission of
information energy by electromagnetic
waves whose wavelengths are measured in small numbers of
centimeter. Microwaves are widely used for point-to-
point communications because their small wavelength allows
conveniently-sized antennas to direct them in narrow beams,
which can be pointed directly at the receiving antenna.
Microwaves are unidirectional. Microwave propagation is a
line of sight propugation.It can support high data rates.

32. There are two types:-
• Terrestrial
Terrestrial:-
Communication through line of sight parabolic dish antenna
located on elevated sites. Long distance communication is
possible.
Satellite:-It is used to point to point broadcast transmission.It
uses uplink &downlink frequency.

36. • Infrared (IR) is invisible radiant energy,
electromagnetic radiation with longer wavelengths than
those of visible light, extending from the nominal red edge of
the visible spectrum at 700 nanometers (frequency 430 THz)
to 1 mm (300 GHz) (although people can see infrared up to at
least 1050 nm in experiments).
• It can be used in development of very high speed wireless
LANs.
• There are two types :-
• Point to point infrared media
• Broad cast infrared media

38. Propagation Methods:-
Ground Wave Propagation-
Radio waves in VLF band propagate in a ground ,or surface
wave. The wave is connected at one end to the surface
of the earth and to the ionosphere at the other.
The range of ground propagation is below 2MHz

40. Sky Wave Propagation:-
Sky waves are reflections from the inosphere.while the wave is in
the inosphere,it is strongly went, or reflected, unlimited back
to the ground. Sky waves in this frequency land are usually
only possible at night when the concentration of ions is not
too great since the ionosphere also tends to attenuate the
signal. The range of this propagation is 2-30MHz.

42. Line-of-Sight Propagation:-
Line-of-sight propagation refers to electromagnetic radiation
including light emission traveling in straight line. The rays or
waves are diffracted,refracted,reflected or absorbed by
atmosphere and abstractions with material and generally can
not travel over the horizon of behind obstacles.
Especially radio signals, like all electromagnetic radiation including
light emission, travel in straight line.