06-03-2013, 12:35 PM
Transmission Media
[attachment=52753]
Introduction
Computer communication involves
encoding data into some form of energy
and sending this across a transmission
medium
This lecture introduces a few basic
transmission concepts as background
Specifically, it examines the properties of
different transmission media
Copper Wire
The most common medium as its is
inexpensive and easy to install
Why copper?
The biggest problem is interference which
results in noise
At its worst when wires run parallel and
close together
Optical Fibre
Also known as glass fibre - a thin glass tube
that reflects light internally and is coated in
plastic for flexibility
Transmitter uses LED or laser and receiver
uses a light sensitive transistor
Advantages
• no electrical interference
• carry a signal much further than copper
• carry more information at a time
• only needs one fibre - unlike copper that requires
a pair to form a circuit
Radio
Broadcast of electromagnetic waves through
the air at radio frequency (RF)
Each computer uses an antenna - no direct
connection is required
Properties vary according to frequency
Size of antenna determines range - 2m pole
across town vs. inside a laptop for a room
[attachment=52753]
Introduction
Computer communication involves
encoding data into some form of energy
and sending this across a transmission
medium
This lecture introduces a few basic
transmission concepts as background
Specifically, it examines the properties of
different transmission media
Copper Wire
The most common medium as its is
inexpensive and easy to install
Why copper?
The biggest problem is interference which
results in noise
At its worst when wires run parallel and
close together
Optical Fibre
Also known as glass fibre - a thin glass tube
that reflects light internally and is coated in
plastic for flexibility
Transmitter uses LED or laser and receiver
uses a light sensitive transistor
Advantages
• no electrical interference
• carry a signal much further than copper
• carry more information at a time
• only needs one fibre - unlike copper that requires
a pair to form a circuit
Radio
Broadcast of electromagnetic waves through
the air at radio frequency (RF)
Each computer uses an antenna - no direct
connection is required
Properties vary according to frequency
Size of antenna determines range - 2m pole
across town vs. inside a laptop for a room