Optic fibre transmission has, in some instances, replaced transmission using co-axial cables and wire pairs. Optic fibres have negligible cross-talk and are less noisy than co-axial cables. Explain what is meant by
cross-talk,
noise.
An optic fibre has a signal attenuation of 
. The input signal to the optic fibre has a power of 
. The receiver at the output of the fibre has a noise power of 
. Calculate the maximum uninterrupted length of optic fibre given that the signal-to-noise ratio at the receiver must not be less than 
.
.
