Hybrid fiber-coaxial

Hybrid Fibre Coaxial (HFC) is a telecommunications industry term for a network which incorporates both optic fibre along with coaxial cable to create a broadband network.

Through the use of each of these technologies, the network is able to take advantage of the benefits and minimise the impacts of the limitations inherent to each.

Optic fibre provides the ability to cover reasonably long distances within minimal amplification and regeneration. However, due to the nature of this technology, and the cost and size of Optic Mux-Demuxers this technology is rarely used to connect the exchanges directly to customers.

Instead, the optic fibre terminates at a network element referred to as a "Gateway". A gateway contains at least one (normally two) optic transcievers and transcievers allowing the signal to transition into a coaxial cable network.

Coaxial cable provides considerable bandwidth capacity, whilst also allowing for the signal to be extracted and inserted ("tapped") with minimal interference to any customers or equipment downstream (further down the cable, away from the Gateway). It also requires far less expense with regards to the equipment required to receive and transmit these signals (as the signal is RF in the coaxial cable). The limitations of this system are that the signal needs to be amplified often to achieve the coverage required, and (due to its carriage through coaxial cable) it is susceptible to interference from external Electrical interference.

Carriers employing an HFC Network have a number of options available regarding the use of the bandwidth available through this system.

• Some use 100% of the bandwidth for broadcast signals.
  • This is normally done for simple Cable TV Networks or other products which will operate on a simplex network.
  • Some asymmetrical services (such as broadband internet) can be operated on a simplex HFC network, using a conventional telephone line to provide the "reverse path".
• Some use a small proportion of the bandwidth to create a "reverse path".
  • This allows monitoring of equipment attached to the network, providing faster identification and diagnosis of faults.
• Some use a larger proportion of the bandwidth to create a "reverse path".
  • This allows products which require a duplex network to operate. Including broadband internet, telephony and interactive television.

HFC Networks are employed by a number of telecommunications companies. Optus in Australia uses an HFC Network to provide Telephony, Broadband Internet and Cable Television. (A trial of Interactive Television was undertaken in 2000, but due to costs and marketing prospects it was not pursued. Recently, sources from within Optus have said that a trial of a new interactive service will begin in Sydney in the near future.)