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    Glossary of Common Terms

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    Fiber-to-the-Home (FTTH)

    “Fiber to the Home” is defined as a communications architecture in which the final connection to the subscriber’s premises is Optical Fiber.

    The fiber optic communications path is terminated on or in the premise for the purpose of carrying communications to a single subscriber.

    In order to be classified as FTTH, the access fiber must cross the subscriber’s premises boundary and terminate

    • inside the premises, or
    • on an external wall of the subscriber’s premises.

    FTTH services may deliver just one application, but generally deliver several such as data, voice and video.

    This FTTH definition excludes architectures where the optical fiber terminates in public or private space before reaching the premises and where the access path continues to the subscriber over a physical medium other than optical fiber (for example copper loops, power cables, wireless and/or coax).

    Definition: Premises, Subscriber

    “Premises” is defined as the subscriber’s home or place of business. In a multi dwelling unit[1] each apartment is therefore counted as one premise.

    “Subscriber” is a premises that is connected to a FTTH network and uses at least one service on this connection under a commercial contract.

    FTTH Electronics

    A typical FTTH network has an “Optical Line Terminal” (OLT) or switch at the “Headend” or “Central Office”

    The OLT or switch converts incoming traffic into laser pulses and sends them down the fiber.

    …And an “Optical Network Terminal” (ONT), media converter, or gateway in the home. The ONT converts the signals from light to electrical signals.

    The ONT contains ports to distribute signals on the existing home wiring (or wirelessly).

    The ONT may be either inside or outside the home.

    Communications Architecture

    The cable plant which connects the service providers/network operators’ premises and subscribers’ premises can be deployed in the following different topologies:

    “Point-to-Point” (P2P [2], Pt-Pt, or PtP) cable plant provides optical fiber paths from a communication node to a single premise such that the optical paths are dedicated to traffic to and from this single location. (Uninterrupted single fiber from last communication switching equipment-point to the premises.)

    “Point-to-Multipoint” (P2MP) cable plant provides branching optical fiber paths from a communication node to more than one premises such that a portion of the optical paths are shared by traffic to and from multiple premises. In generic terms this is a tree topology. [3]

    “Ring” cable plant provides a sequence of optical fiber paths in a closed loop that connects a series of more than one communication node.

    Note that from these definitions it is not possible to identify the access protocol used over the cable plant. This is discussed below. Networks are either “passive” or “active”.

    It is possible for a network to be built so that a common cable plant can include a mix of different architectures, or be re-configured over time to support different architectures, to allow for mixed user categories, to allow access diversity for reliability, and for future flexibility and network longevity.

    • PON (Passive Optical Network)
      • Incorporates a signal divider, such as an optical power splitter
      • One fiber at the central office feeds many fibers in the field
      • G-PON (Gigabit PON) and GE-PON (Gigabit Ethernet-PON) are the most common architectures
    • Point-to-Point (“Active Ethernet”)
      • One fiber in the headend = one fiber in the field

    Network Size

    The size of FTTH Networks is described in the following terms:

    The number of “Homes Passed” is the potential number of premises to which an operator has capability to connect in a service area, but the premises may or may not be connected to the network. [4]

    This definition excludes premises that cannot be connected without further installation of substantial cable plant such as feeder and distribution cables (fiber) to reach the area in which a potential new subscriber is located.

    The number of “Homes Connected” is the number of premises that are connected to an FTTH network.

    With respect to a particular network, the following three definitions are measures of network utilization and calculated as follows:

    The “Penetration Rate” - “Homes Connected” divided by the number of premises in a served area.

    The “Take Rate” - “Subscribers” divided by “Homes Connected”. [5]

    The “Connect Rate” - “Homes Connected” divided by “Homes Passed”

    Network Usage

    FTTH networks may be dedicated to the services of a single retail service provider, or made available to many retail service providers, who may connect to the network at the packet, wavelength or physical layer.

    “Exclusive Access” refers to the situation where a single retail service provider (who may or may not be the network operator) has exclusive use of the FTTH network.

    “Open Access (Packet)” refers to the situation where multiple retail service providers may use the FTTH Network on an equable base by connecting at a packet layer interface and compete to offer their services to end users.


    [1] multi-tenanted unit in some countries
    [2] the abbreviation P2P is sometimes also used to describe peer-to-peer-networks, e.g. to exchange files over the internet. This P2P is not connected to the point-to-point definition in this document.
    [3] P2MP is often referred as “Passive Optical Network” (PON), whereby the path from the active or powered communication node to the terminating fiber location has no active or powered elements.
    [4] Typically new service activation will require the installation and/or connection of a drop cable from the homes passed point (e.g. fiber-pedestal, handhole, chamber, utility-pole) to the premises, and the installation of subscriber premises equipment, including an ONT (Optical Network Termination) device at the premises.
    [5] It is expressed as a percentage. “Take rates” can be based on each type of service, for example, data take rates, video take rates, and voice take rates, or triple/quadruple services take rates


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