The Presentation describes about the Transmission media and in detail about coaxial cable,Twisted pair, Fiber optics, Power lines and their comparisons

1. TRANSMISSION MEDIA
By
S.Rajapriya,MS(IT).,
Assistant Professor of IT
V.V.Vanniaperumal College for Women

2. TRANSMISSION MEDIA
•A transmission medium is a physical path between the transmitter
and the receiver (i.e) it is the channel through which data is sent from
one place to another.
• Transmission Media is broadly classified into the following types:

3. GUIDED TRANSMISSION MEDIA
•It is also referred to as Bounded transmission media.
•Signals being transmitted are directed and confined in a narrow
pathway by using physical links.
•Features:
1. High Speed
2. Secure
3. Used for comparatively shorter distances
There are 3 major types of Guided Media:

4. 2.1 MAGNETIC MEDIA
One of the most convenient way to transfer data from one computer to
another, even before the birth of networking, was to save it on some storage
media and transfer physical from one station to another.
 For example, a bank has to handle and transfer huge data of its customer,
which stores a backup of it at some geographically far-away place for security
reasons and to keep it from uncertain calamities.
 If the bank needs to store its huge backup data then its transfer through
internet is not feasible.
The WAN links may not support such high speed.Even if they do; the cost is
too high to afford.
In these cases, data backup is stored onto magnetic tapes or magnetic discs,
and then shifted physically at remote places.

5. 2.2 TWISTED PAIR
Although the bandwidth characteristics of magnetic tape are excellent,
the delay characteristics are poor.
A twisted pair consists of two conductors (normally copper), each with
its own plastic insulation, twisted together, as shown in fig. below
One of the wires is used to carry signals to the receiver, and the
other is used only as a ground reference. The receiver uses the
difference between the two.
In addition to the signal sent by the sender on one of the wires, noise
and crosstalk may affect both wires and create unwanted signals.

6. TWISTED PAIR
By twisting the pairs, a balance is maintained.
The number of twists per unit of length(e.g., inch) has some effect on
the quality of the cable.
Twisted Pair is of two types:

7. UNSHIELDED TWISTED PAIR (UTP)
This type of cable has the ability to block interference and does not
depend on a physical shield for this purpose.
 It is used for telephonic applications.
Advantages:
i. Least expensive
ii. Easy to install
iii. High speed capacity
iv. Susceptible to external interference
v. Lower capacity and performance in comparison to STP
 UTP has seven categories, each suitable for specific use. In
computer networks, Cat-5, Cat-5e, and Cat-6 cables are mostly
used.

8. SHIELDED TWISTED PAIR (STP)
This type of cable consists of a special jacket to block external
interference.
 It is used in fast-data-rate Ethernet and in voice and data channels of
telephone lines.
Advantages:
i. Better performance at a higher data rate
ii. Eliminates crosstalk
iii. Comparitively faster
iv. Comparitively difficult to install
v. More expensive
vi. Bulky

9. 2.3 COAXIAL CABLE
Coaxial cable (or coax) carries signals of higher frequency ranges than
those in twisted pair cable.
It has an outer plastic covering containing 2 parallel conductors each
having a separate insulated protection cover.
 Coaxial cable transmits information in two modes:
1. Baseband mode
2. Broadband mode
 Cable TVs and analog television networks widely use Coaxial cables.

10. COAXIAL CABLE
Advantages:
i. High Bandwidth
ii. Better noise Immunity
iii. Easy to install and expand
iv. Inexpensive
Disadvantages:
i. Single cable failure can disrupt the entire network

11. 2.4 POWER LINES
Power Line communication (PLC) is Layer-1 (Physical Layer) technology which
uses power cables to transmit data signals.
In PLC, modulated data is sent over the cables. The receiver on the other end de-
modulates and interprets the data.
Because power lines are widely deployed, PLC can make all powered devices
controlled and monitored. PLC works in half-duplex.
There are two types of PLC:
Narrow band PLC
Broad band PLC
Narrow band PLC provides lower data rates up to 100s of kbps, as they work at
lower frequencies (3-5000 kHz).They can be spread over several kilometers.
Broadband PLC provides higher data rates up to 100s of Mbps and works at
higher frequencies (1.8 – 250 MHz).They cannot be as much extended as
Narrowband PLC.

13. 2.5 FIBER OPTIC CABLE
Structure of Optical Fiber : It has three parts
• Core: It is a central tube as shown in the diagram. It is of skinny size and made
up of the optically transparent dielectric medium. It carries the light from the
transmitter to the receiver.The diameter of the core varies from 5um to 100um.
• Cladding: it is the outer optical material surrounding the core. Its reflective index
is lower than the core. It helps to keep the light within the core as it uses the
phenomena of total internal reflection.
• Buffer coating: It is the plastic coating which protects the fiber. It is made up of
silicon rubber. The diameter of the fiber after the coating is 250-300um.

14. TRANSMISSION OF LIGHT THROUGH FIBER
A fiber optic cable is a light pipe which is used to carry a light beam
from one place to another.
 Light is an electromagnetic signal and can be modulated by
information.
Since the frequency of light is extremely high hence it can
accommodate wide bandwidths of information, also higher data rate
can be achieved with excellent reliability.
The modulated light travel along the fiber and at the far end, are
converted to an electrical signal by means of a photo electric cell.
Thus the original input signal is recovered at the far end.
FOC may be multimode or signal mode.
Multimode fibers use multiple light paths whereas signal mode
fibers allow a single light path and are typically used with laser
signaling.

15. FIBER OPTIC – ADVANTAGES & DISADVANTAGES
Advantages:
i. Increased capacity and bandwidth
ii. Light weight
iii. Less signal attenuation
iv. Immunity to electromagnetic interference
v. Resistance to corrosive materials
Disadvantages:
i. Difficult to install and maintain
ii. High cost
iii. Fragile

16. COMPARISON OF FIBER OPTICS AND COPPER
WIRE
S.No. Basis Fiber Optics Copper Wire
1. Data Carrier It carries data in the form of light.
It carries data in the
form of electric
signals.
2. Bandwidth It offers higher bandwidth.
It offers lower
bandwidth.
3. Structure
It is thin, lighter in weight and smaller
in size.
It is heavier and
thicker.
4. Environment
It can be laid in different environment
because it is more resistant to
corrosive materials.
It cannot be laid in
different environment
because it is more
prone to corrosive
materials.
5. Attenuation Attenuation is very low. Attenuation is high.

17. S.No. Basis Fiber Optics Copper Wire
6. Interface
As in this data travel in the form of light,
they are not affected by electrical and
magnetic interface.
As in this data travel in
the form of electric
signals, they are affected
by electrical and
magnetic interface.
7. Security
They provide security against the
wiretappers, because there is no leakage
of light and are difficult to tap.
They does not provide
security against the
wiretappers, because
there is leakage of
signals and are easy to
tap.
8. Cross-talk problem There is no such kind of any problem.
These are prevalent this
problem.
9.
Effect on charge
carriers
In this charge carriers are photons, they do
not carry any charge, so they does not get
affected.
In this charge carriers
are electrons, they carry
negative charge, so they
get affected when they
move in a wire.
10. Break-ability They are easily breakable.
They cannot be easily
broken.
11. Installation Cost Installation Cost is high. Installation Cost is less.