TRANSMISSION MEDIA

Introduction
Transmission Media:-
A transmission media can be defined as anything that can carry signal from source to destination.
Example:- Let the two friends are having dinner conversation . Here transmission media is air.
The transmission media may be the air , fiber-optics cables , metallic cables etc.
Here in Computer Network , transmission media is the medium to transfer the data from one computer physical layer to another computer physical layer .
Guided Media
It provides a conduit (connection) from one device to another.
It includes
(1)Twisted-pair cable
(2)Coaxial cable
(3)Fiber-optics cable
Twisted-pair & Coaxial cable transfer the signals in the form of electric current.
Fiber-optics cable transfer the signals in the form of light.
Twisted Pair Cable:-
It is ordinary copper wire that is used in home & business computer . To reduce the electromagnetic induction between pairs of wires two insulated copper wire are twisted.
It carries signals below frequency range below 100kHz.
Connector:-
RJ45 clit (Registered jack 45 clit)
It is of two type
(1)UTP (Unshielded Twisted-Pair)
(2)STP (Shielded Twisted-Pair)
It is applied for
(1)Telephone wires
(2)Creating a LAN
UTP:-
The Twisted-pair cable having no external coating is known as Unshielded Twisted-Pair cable . One of the wire is used to carry the signals & another is used to avoid the unwanted signals.
ADVANTAGE:-
* It is very less expensive
* It is easy for installation
DISADVANTAGE:-
* It covers very small distance i:e: up to100 m.
STP:-
The Twisted-pair cable having extra shielding is known as Shielded Twisted –Pair cable . Extra shielding protects the cable from interference.
ADVANTAGE:-
* It gives greater protection than UTP.
* Better electrical characteristic than UTP.
DISADVANTAGE:-
* These are high cost , heavier in structure , difficult to install.
Coaxial Cable:-
This cable carries signals of higher frequency than the twisted-pair cable. Here the frequency ranges from 100-500kHz.
It transmits both analog and digital signals
Connector:-
T-connector/BNC connector.
It is of two types
(1)Base band
(2)Broad band
It is applied for
(1)Telephone networks
(2)Cable TV network
(Coaxial cable)
BASEBAND:-
This type of Coaxial cable is used for digital transmission . It’s resistance is 50Ω. Transmission is bidirectional.
ADVANTAGE:-
* It is very less expensive
* It is easy for installation
DISADVANTAGE:-
* It is limited only for data and voice transmission.
BROADBAND:-
This cable are much longer than Baseband and can transmit number of data, voice & videos at a time. It’s resistance is 75Ω. This cable is basically used for analog transmission.
ADVANTAGE:-
* It covers greater distance and supports greater bandwidth.
* It can support data, voice & video at a time.
DISADVANTAGE:-
* It is very difficult to maintain.
Fiber-optics Cable:-
A Fiber-optics Cable is made of glass or plastics & transmits signals in the form of light.
In this case the principle of Total Internal Reflection works i:e: If angle of incidence is greater than the critical angle of reflection then the light turn back and travel in the same medium.
Here core is surrounded by cladding . The beam of light is reflected by the cladding and transmitted through the core. cladding
core
CONTD….
This cable consist of an optical transmitter at sender side which is used to transmit the signal and an optical receiver at receiver side which is used to receive the transmitted signal.
Fiber-optics Cable is divided to two types
(1) Single-mode Fiber-optics
(2) Multi-mode Fiber-optics
Fiber-optics Cable
SINGLE-MODE:-
It is a single strand up glass fiber of diameter of 8.30 to 10 microns that has one mode of transmission.
ADVANTAGE:-
* It supports high band width.
* It has a higher resistance than multi-mode.
DISADVANTAGE:-
* It is of high cost & one mode transmission leads to traffic problem.
MULTI-MODE:-
The diameter is 50-100 microns. Due to the multiple mode single signal is splitted into no of channels and transmitted towards the receiver.
ADVANTAGE:-
* It supports high frequency and high bandwidth .
* In this case signal suffers less attenuation .
DISADVANTAGE:-
* It is very difficult to install and maintain.
* It is always unidirectional and more expensive.

Unguided Media
Unguided Media transport electromagnetic waves of frequency ranging from 3kHz-400THz.
It has no physical conductor also called as wireless communication.
According to the wave propagation it is divided to 3 types
(1) Radio Wave
(2) Micro wave
(3) Infrared
Radio Waves:-
The transmitted signal ranges from 3kHz to 1GHz . It is omnidirectional .
APPLICATION:- It is used in Radio, Television.
ADVANTAGE:- It can be transmitted through a wall.
DISADVANTAGE:- It supports less data.
Microwaves:-
The transmitted signal ranges from 1GHz to 300GHz . It is unidirectional.
APPLICATION:-It is used in satellite network & cellular telephone .
ADVANTAGE:- It is easy to maintain & install.
DISADVANTAGE:- It requires line of sights.
Infrared:-
The transmitted signal ranges from 300GHz to 400THz . It is used for short-range communication.
APPLICATION:- It is used in IrDA(Infrared Data Association) port. This port is used for wireless keyboard to communicate with a PC.
ADVANTAGE:- It supports higher bandwidth.
DISADVANTAGE:- It is limited in distance i:e: upto 8m. It is difficult to maintain.