RF amplifiers are used at intervals to overcome cable attenuation and passive losses of the electrical signals caused by splitting or "tapping" the coaxial cable. The coaxial trunk portion of the network connects 25–2000 homes (500 is typical) in a tree-and-branch configuration off of the node. For example, the downstream signal could be on a wavelength at 1490 nm and the return signal could be on a wavelength at 1310 nm. Optical filters are used to combine and split optical wavelengths onto the single fiber. If there are not many fiber-optic cables to the node, wavelength division multiplexing can be used to combine multiple optical signals onto the same fiber. The optical portion of the network provides a large amount of flexibility. This electrical signal is then outputted through coaxial cable to form a coaxial trunk. In North America, this reverse signal is a modulated RF ranging from 5–42 MHz while in other parts of the world, the range is 5–65 MHz. The fiber optic node also contains a reverse- or return-path transmitter that sends communication from customers back to the headend. As of 2015, the downstream signal is a RF modulated signal that typically begins at 50 MHz and ranges from 550–1000 MHz on the upper end.
Fiber optic cables connect the headend or hub to optical nodes in a point-to-point or star topology, or in some cases, in a protected ring topology.Ī series of taps (servicing multiple rooms in a hotel) from a distribution line, with terminators on unused ports Fiber optic nodes Ī fiber optic node has a broadband optical receiver, which converts the downstream optically modulated signal coming from the headend or hub to an electrical signal going to the customers.
This optical transmitter converts the electrical signal to a downstream optically modulated signal that is sent to the nodes. The various services are encoded, modulated and upconverted onto RF carriers, combined onto a single electrical signal and inserted into a broadband optical transmitter.
Some master headends also house telephony equipment (such as automatic telephone exchanges) for providing telecommunications services to the community.Ī regional or area headend/hub will receive the video signal from the master headend and add to it the public, educational, and government access (PEG) cable TV channels as required by local franchising authorities or insert targeted advertising that would appeal to a local area. A master headend will usually have satellite dishes for reception of distant video signas as well as IP aggregation routers. The fiber optic network extends from the cable operators' master headend, sometimes to regional headends, and out to a neighborhood's hubsite, and finally to a coaxial cable node which serves anywhere from 25 to 2000 homes. The fiberoptic trunk lines provide adequate bandwidth to allow future expansion and new bandwidth-intensive services such as internet access through DOCSIS. At the local community, a box called an optical node translates the signal from a light beam to radio frequency (RF), and sends it over coaxial cable lines for distribution to subscriber residences. In a hybrid fiber-coaxial cable system, the television channels are sent from the cable system's distribution facility, the headend, to local communities through optical fiber subscriber lines. It has been commonly employed globally by cable television operators since the early 1990s. Hybrid fiber-coaxial ( HFC) is a telecommunications industry term for a broadband network that combines optical fiber and coaxial cable. ( Learn how and when to remove this template message) JSTOR ( August 2016) ( Learn how and when to remove this template message).Unsourced material may be challenged and removed.įind sources: "Hybrid fiber-coaxial" – news Please help improve this article by adding citations to reliable sources.