In a hybrid fiber coaxial (HFC) network, optical fiber and coaxial cables are used in together but in different parts of the network to carry broadband data. In an HFC network, a shared coaxial cable is used to connect to subscribers on one side while on the other side the coaxial cable is connected to remote equipment providing the conversions to/from a fiber connection. Hybrid fiber/coax (HFC) systems are now a major form of broadband access worldwide, having evolved from a simple multichannel video broadcasting system to a two-way interactive multimedia digital network. The core protocols that enable bidirectional data transmission over the cable network are defined in the Data-Over-Cable Service Interface Specification (DOCSIS), developed by CableLabs.
The coaxial network is shared among several subscribers, typically several hundreds. The bandwidth of the shared coaxial cable is divided into various frequency bands, most allocated to analog and digital video (downstream only) and some to data communications (downstream and upstream). This high degree of sharing limits drastically per-subscriber capacity in dense deployments.