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Fiber Optics in Telecommunications

Telecommunications system based on fiber-optic cables are designated according to the distance to the final end point, resulting in a number of suffixes:

Fiber to the node / neighborhood [FTTN) / Fiber to the cabinet (FTTCab]
Fiber to the curb [FTTC]
Fiber to the building [FTTB]
Fiber to the home [FTTH]

The diagram left illustrates how the FTTX architectures varies, depending upon the distance between the optical fiber and the end-user.

The building on the left is the central office

The building on the right is one of the buildings served by the central office.

The dotted rectangles represent separate living or office spaces within the same building.

Data rates vary according to the exact protocol used and according to how close the customer is to the cabinet.

High speed communications protocols such as broadband cable access ([DOCSIS] or some form of DSL are used between the cabinet and the customers.

Fiber to the Node

Fiber to the node [FTTN], fiber to the neighborhood or fiber to the cabinet (FTTCab], is a telecommunication architecture based on fiber-optic cables run to a cabinet serving a neighborhood.

Customers connect to this cabinet using traditional coaxial cable or twisted pair wiring.

The area served by the cabinet is usually less than 1,500 m in radius and can contain several hundred customers. If the cabinet serves an area of less than 300 m in radius then the architecture is typically called fiber to the curb.

Fiber to the node allows delivery of broadband services such as high speed internet.

Unlike the competing fiber to the premises [FTTP] technology, fiber to the node can use the existing coaxial or twisted pair infrastructure to provide last mile service. For this reason, fiber to the node costs less to deploy. However, it also has lower bandwidth potential than fiber to the premises.

Fiber to the Curb

Fiber to the curb [FTTC], is where fiber-optic cables run to a platform that serves several customers. Each of these customers has a connection to this platform via coaxial cable or twisted pair.

Fiber to the curb allows delivery of broadband services such as high speed internet.

FTTC is distinct from FTTN or FTTP by the placement of the cabinet. FTTC will be placed near the "curb" which differs from FTTN which is placed far from the customer and FTTP which is placed right at the serving location.

Unlike the competing fiber to the premises (FTTP) technology, fiber to the curb can use the existing coaxial or twisted pair infrastructure to provide last mile service. For this reason, fiber to the curb costs less to deploy. However, it also has lower bandwidth potential than fiber to the premises.

Fiber In The Loop

Fiber In The Loop [FITL] is a system implementing or upgrading portions of the POTS local loop with fiber optic technology - from the central office of a telephone carrier to a remote Serving Area Interface (SAI) located in a neighborhood or to an Optical Network Unit [ONU] located at the customer premises.

Generally, fiber is used in either all or part of the local loop distribution network. FITL includes various architectures, such as fiber to the curb [FTTC], fiber to the home [FTTH] and fiber to the premises [FTTP].

Cost Considerations

The closer the fiber head, the higher the cost of construction and the higher the channel capacity. Residential areas already served by balanced pair distribution plant call for a trade-off between cost and capacity. In places not served by metallic facilities, little cost is saved by not running fiber to the home.

Hybrid Fibre-Coaxial

A similar network called a hybrid fibre-coaxial [HFC] network is used by cable television operators but is usually not synonymous with "fiber In the loop", although similar advanced services are provided by the HFC network.

Fiber Network Deployments

FTTH is currently complicated in many markets by monopoly ownership of the local loop. FTTH and Local Loop Unbundling [LLU] are contensious issues, and no easy resolution is available.

Because of this, most FTTH deployments are being done by property developers, using the network as a major selling point.

Cabinetization is being promoted as one resolution, but that also have a complex set of considerations.

Governments are intervening in an effort to speed up the investment in FO networks, seen as a driver of future economic growth.

Next: Cabinetization