Fiber to the x

A schematic illustrating how the FTTX architectures vary with regard to 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.

Fiber to the x (FTTX) is a generic term for any network architecture that uses optical fiber to replace all or part of the usual copper local loop used for telecommunications. The four technologies, in order of an increasingly longer fiber loop are:

• Fiber to the node / neighborhood (FTTN) / Fiber to the cabinet (FTTCab)
• Fiber to the curb (FTTC) / Fibre to the kerb (FTTK)
• Fiber to the building (FTTB)
• Fiber to the home (FTTH)

In the actual deployments, the difference between FTTN and FTTC is quite subtle and is mostly that the latter is nearer the customer than the former.

The poorly-defined term fiber to the premises (FTTP) is sometimes used to describe FTTH and/or FTTB.

Fibers

Fiber to the node

Fiber to the node (FTTN), also called 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. High speed communications protocols such as broadband cable access (typically DOCSIS) or some form of DSL are used between the cabinet and the customers. The data rates vary according to the exact protocol used and according to how close the customer is to the cabinet.

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 Telcommunications Enclosure

Diagram originally published by the Fiber Optics LAN Section of the Telecommunications Industry Association

Fiber-to-the-Telecommunications-Enclosure (FTTE) is a standards-compliant structured cabling system architecture that extends the optical fiber backbone from the equipment room, through the telecom room, and directly to a telecommunications enclosure (TE) installed in a common space to serve a number of users in a work area. Its implementation is based on the TIA/EIA-569-B “Pathways and Spaces” standard, which defines the Telecommunications Enclosure (TE), and TIA/EIA-568-B.1 Addendum 5, which defines the cabling when a TE is used. The FTTE architecture allows for many media choices from the TE to the work area; it may be balanced twisted pair copper, multimode optical fiber, or even wireless if an access point is installed in or near the TE.

Depending on the user’s needs, FTTE can be deployed in low-density or high-density configurations. A low-density system might use one or two inexpensive 8-port Ethernet mini-switches as an example (these switches have eight 10/100 Mbit/s Ethernet copper ports and one 1 Gbit/s Ethernet fiber uplink). A high-density FTTE design might use commonly available 24- or 48-port switches (these switches are configured with one 1 Gbit/s uplink port per twelve 100BASE-TX user ports). This relatively high work area-to-backbone port ratio provides better performance than is typically provided to enterprise users. Both low and high-density FTTE architectures provide excellent performance in terms of bandwidth delivered to the work area.

• Advantages
  • Low Cost
  • Non-blocking or low-blocking performance better supports convergence
  • Extremely flexible to deploy; supports Moves, Adds & Changes
  • Enables consolidation of electronics into a centralized Telecommunications Room
  • Allows the use of a variety of media from the TE to the user
• Disadvantages
  • TE location is near the user and must be secured

Fiber to the curb

Fiber to the curb (FTTC), also called fibre to the kerb (FTTK), is a telecommunications system based on 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. High speed communications protocols such as broadband cable access (typically DOCSIS) or some form of DSL are used between the cabinet and the customers. The data rates vary according to the exact protocol used and according to how close the customer is to the cabinet.

FTTC is subtly distinct from FTTN or FTTP (all are versions of Fiber in the Loop). The chief difference is 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.

In the United States of America, the largest deployment of FTTC was carried out by BellSouth Telecommunications. With the acquisition of BellSouth by AT&T, deployment of FTTC will end. Future deployments will be based on either FTTN or FTTP. Existing FTTC plant may be removed and replaced with FTTP.

See also

• Fiber to the premises
• Hybrid fibre-coaxial
• Fiber Optics LAN Section of the Telecommunications Industry Association
• Fiber Optics Association
• BICSI

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 (residential and/or business). 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).

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

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.

Technologies

The two main technologies used for these architectures are VDSL2 (used in FTTN, FTTC and in some FTTB deployments) and PON (the one used in FTTH and in some FTTB deployments)

External links

• Fiber to the Home Council
• Fiber to the Home Council Europe
• The Fiber Optics Weekly Update
• KMI Research Homepage
• FTTH Blog Daily updates on the business and technology of FTTH
• Telephony Magazine - FTTH One-Stop news, metrics, technology, regulatory information and industry commentary
• Kingfisher International Application Notes Fiber Optic Testing information about FTTH backbone Terminology.
• ADC Hosts First Fiber-to-the-Premises Leadership Symposium; Nationwide Series Brings Together Industry Leaders for Education, Discussion of FTTP Deployment.
• Can You Say FTTN? Annie Lindstrom, Telephony Online, Jan 22, 2001
• SBC clarifies FTTN, FTTP plans Ed Gubbins, Telephony Online, Nov 12, 2004
• Easy as 1,2,3,...4 Don McCullough,"OSP Magazine", October 2005