The difference is that fiber-optics use light pulses to transmit information down fibre lines instead of using electronic pulses to transmit information down copper lines. Today all core networks are based on fibre due to higher speed capacity and greater resistance to electromagnetic noise such as “alien cross talk” from other nearby cabling. In addition, fibre optic cables cost much less to maintain and are a more modern form of data transport. However copper is often used as the last mile to an exchange where fibre is present.