ALBEDO AT.2048
4
1.2 Transmission Medium
The transmission medium can be defined as the environment where a signal is
transmitted, be it material (electrical wires, optical fiber, open air, etc.) and nonma-
terial, or vacuum, through which only electromagnetic waves are propagated.
The material transmission medium can be divided into two main groups:
1. A
conductive medium
, in which the information is transmitted in the form of
electrical impulses. Typical examples of this medium are twisted-pair and
coaxial cables.
2. A
dielectric medium
, in which the information is transmitted in the form of
radioelectrical or optical signals; for example, the atmosphere and optical fiber.
Transmitted signal
Attenuation
Distortion
Noise
Received signal
Source
Transmitter
T
ran
smission medium
Receiver
Sink
di
st
a
nc
e
(
d)
P
Tx
P
Rx
Figure 3
Effects of attenuation, distortion, and noise on transmission.
Sampling times
Data received
Original data
1
0
0
0
1
0
1
0
The propagation of signals over one of these media is what we call transmission.
The success of transmission of information in telecommunications networks de-
pends basically on two factors: the quality of the signal transmitted, and the quality
of the transmission medium used. In addition, there are natural forces that can resist