(a)[2]
State two advantages of sending data in digital form instead of analogue form.
(b(i))[2]
An electromagnetic wave with frequency $1.36 \times 10^{14}\,\text{Hz}$ travels in an optic fibre at $2.07 \times 10^8\,\text{m s}^{-1}$. For this wave, determine the ratio of wavelength in free space to wavelength in fibre.
(b(ii))[3]
The signal attenuation per unit length in the fibre is $0.40\,\text{dB km}^{-1}$. The input power is $1.5\,\text{mW}$ and the output power is $0.060\,\text{mW}$. Calculate the fibre length.