Network covers a wide geographical area such as a state or country cable transmits data as pulses of light rather than as electricity

Yep, because electricity is much more susceptible to interference, such as through electromagnet interference, which would significantly degrade signals, especially over long distances.

Pulses of light through fibre optic cables are both faster and less susceptible to interference. Though come as a greater price cost, and the cables are unable to make shape bends like electrical cables do, as the glass tube inside must retain it's refractive index in order for light to travel down the cable.