HFC - Basic Principles
Updated: Aug 30, 2021
HFC: Hybrid Fiber-Coaxial - is a telecommunications industry term for a broadband network that combines optical fiber and coaxial cable. It has been commonly employed globally by cable television operators since the early 1990s
What is HFC and how does it work?
During the late 80's and the early 90's, HFC changed people's lives. Cable TV operators were in such high demand that an affordable solution had to be found to reach every household in a short period of time.
HFC was an inexpensive solution that allowed bringing fiber to the neighborhood and, once there, the cabling was distributed through the different homes to reach every house. This led to the construction of a hybrid network that has continued to be used over time and integrates fiber optic cables with coaxial cables known as HFC.
How does it work?
Coaxial hybrid fiber or Hybrid Fiber-Coaxial is a network that incorporates fiber optics but does not reach your home directly. Before reaching your home, a coaxial cable is used to distribute the network to all the houses in your building or neighborhood.
There is a first part that connects the fiber optic to the zonal nodes and a second part that connects the zonal node to your home with coaxial cable. In most cases, this coaxial cable is only in the last section that goes from the neighborhood or housing development to the house and is the one we plug into the router.
There are also differences in the way the data is transported: it is sent through electrical signals and can be susceptible to electromagnetic interference or worsen the signal in the cable, due to the length of the cable until it reaches the house, which often requires the use of amplifiers or regenerators.
The importance to know about DOCSIS standard
To understand more about coaxial cable or HFC systems, we must also understand that DOCSIS stands for Data Over Cable Service Interface Specification.
DOCSIS was launched in its first version in the late nineties, in 1997. It is still used today by some operators to achieve Internet access over HFC or coaxial fiber and not FTTH as such.
Since 1997 until today, DOCSIS versions have been improved, being the last one in March 2014 where cable connections almost reach the capabilities of "pure" FTTH fiber networks that do not use this coaxial cable to reach our home.
This connection provides us with a series of requirements necessary for the highest possible speed to be achieved over these cables. The requirements have advanced to our days and we get higher speed and cost reduction, energy saving, etc.
The installation is different from DOCSIS or even FTTH since in the communications room of the building you do not get to see such a complex installation as in the case of optical fiber. In this case we will simply see a coaxial splitter with the outputs corresponding to the house per floor.
When HFC is installed in a building, there will be one of these installations on each floor of the building along with the main installation. In most cases, the main installation is hidden in the block and is the one that outputs all the coaxial cables.