Basic Description of a FTTH Network Infrastructure

To describe an FTTH infrastructure network, it is essential to understand some of the basics. An FTTH network will normally form part of an existing access network, connecting a large number of end users back to a central point known as an Access Node. Each Access Node will contain the required active transmission equipment used to provide the applications and services over optical fibre to the subscriber. Each Access Node is served by a larger metropolitan or urban network fibre ring, connecting other Access Nodes throughout a large municipality or region.

Access Networks may connect by optical fibre some of the following:

  • Fixed wireless networks (for example Wireless LAN or WLANs)
  • Mobile network base stations (masts)
  • A large number of subscribers in residential houses, terraces or blocks of flats and multi-dwelling units (MDUs)
  • Larger buildings such as schools, hospitals and businesses
  • Key security and monitoring structures like surveillance cameras, security alarms and control devices Therefore, a FTTH network may be considered part of the FTTX area or Access Network as shown in the diagram below.

    • For a detailed explanation of the above, please refer to the planned Cenelec publication described in section 1.6

    1 FTTH Architecture PON versus P2P Ethernet

    As this document only describes the passive infrastructure, it will not go into any depth on architecture.
    Basically there are two options in architecture that are important for the choice of passive infrastructure.

    The drawings below show the PON and P2P Ethernet options schematically. The difference in the two options is mainly the number of fibres in the feeder cable.

    The PON architecture is based on one single optical driver for up to 64 users (in the future 128 users.) Passive
    splitters divide the signal somewhere in the network to the different users. The splitters can be placed in the Access Node or in one of the distribution points.

    The P2P Ethernet Architecture has one optical port for every user thus creating a dedicated fibre connection from the POP to each individual user.

    If the passive infrastructure needs to be able to handle both architectures it is necessary to calculate the highest fibre count in the feeder.

    2 FTTH Network Infrastructure Environment

    The deployment of fibre closer to the subscriber base will require that consideration be given to infrastructure deployment on public and private land, and also within public and private properties. These environments can be broadly split into:

  • City
  • Open Residential
  • Rural

    • Apartment blocks or MDUs can be considered as part of all the above. Each environment offers different customer densities (per sq km), and hence different challenges in providing a suitable infrastructure solution.

    The main influences for the fibre infrastructure deployment costs will be determined by:

  • FTTH environment - as described above
  • Size of the FTTH network
  • Initial deployment cost of the infrastructure elements (this is part of the overall Capex costs)
  • Ongoing costs for network operation and maintenance (part of the overall Opex costs)
  • Type of FTTH area e.g. Greenfield, Brownfield, or Overbuild.
  • Architecture (PON, P2P,..)
  • Local conditions e.g. local labour costs, local authority restrictions (traffic control) and others

    • The fibre deployment costs can be optimised by using a range of deployment technologies broadly grouped below. These are described in further detail later in this paper.

  • Conventional underground duct and cable
  • Blown microducts and cable
  • Direct buried cable
  • Aerial cable
  • Other "Rights of Way" solutions

     

    For each environment, the optimal deployment solution will need to be determined by efficient infrastructure network design.

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