Information may be carried by means of various channels of communication. Name examples, one in each case, of devices where information is carried to the device using
a wire pair,
a coaxial cable,
microwaves.
State two advantages of optic fibres as compared with coaxial cables for long-range communication.
An optic fibre has length 
and an attenuation per unit length of 
. The input power to the fibre is 
. At the receiver, the noise power is 
. The signal-to-noise ratio at the receiver is 
.
Calculate the ratio, in 
, of the input power to the noise power at the receiver.
Use your answer in (i) to determine the input power .
.
.
