Fibre optic cable (glass) can be used to provide a service to a customer premises. Fibre is usually a single frequency using a laser, so not actually broadband at all. Whilst speeds to change with distance on fibre services, they are so high that services are sold with specific speeds which do not vary. Various services are available, see each service description for the speeds that are offered.
Most services sold by other companies as fibre are not, in fact, fibre optic services to your premises. All Internet access services, even ADSL from the exchange, make use of fibre optic cable for part of the service, but what matters for speed and reliability is the weakest link, which is normally the bit to your home.