What is FTTB and which benefits for a coaxial fibre connection?

The FTTB (Fibre to the Home or Fibre to the Basement) is an access network architecture based on a mix of technologies. From a PoP (Point of Presence) or a FCP (Fibre Concentration Point) to the entry of the building to be connected, the old copper pairs are replaced with next generation fibre solutions. Yet, the last mile access, between the optical distribution point installed at the building entry’s level and each dwelling or business premises, other active technologies are used to ensure the data transfer such as:

 

  1. the xDSL (copper phone cable).
  2.  

    This technology can be implemented so to provide access to very high speed networks for a subscriber with a sufficiently short copper telephone line which is also connected to a fibre optic distribution frame. The connection to FTTB networks via the telephone line allows downstream speeds of 30Mbps and more.

     

  3. the DOCSIS (coax cable installed for enabling acces to TV services).
  4.  

    In this configuration, two situations are commonly met:

    • Whenever telecom operators install the last amplifier at the buildin’s entry level, we can also consider this network as a FTTLA (Fibre to the Last Amplifier). Thus, on the ground floor or in the building’s basement, depending on the configuration of each site, each pair of fibres terminates in an opto-electrical node, enabling all subscribers to be served. This type of connection allows downstream speeds of up to 1Gbit/s.
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    • In case of "HFC" (Hybrid Fibre Coaxial) networks, where each optical node serves a larger number of houses or business premises, the provided data rates are lower than in FTTLA configurations. Generally, this network configuration offers downstream speeds of up to 30Mbit/s.
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fttb networks enable fibre optics to get as close as possible to the subscriber's premises but without accessing the home or enterprise

 

FTTB networks enable access to very high speed networks at much lower costs than those associated with FTTH deployments, where fibre optic network ends at the wall mount OTO (Optical Telecommunications Outlet) located inside the subscriber's premises. By contrast, while FTTH networks offer symmetrical access speeds, FTTB networks provide for asymmetrical speeds: subscribers benefit from much higher downstream speeds than upstream speeds.

NGN access networks to cut off CAPEX and OPEX: no optical outlets to install

 

in FTTB network configurations fibre optics termination takes place in a street cabinet or an outdoor closure mounted at the foot of the building

 

Being the second most performant solution after Fibre to the Home, Fibre to the Building brings the optical signal as close as possible to subscribers, without entering their homes or business premises. As the last network segment consists of non-fibre cabling solutions, installed over short distances and immediately available, telecom operators are able to guarantee very high speeds to subscribers within much shorter time frames. This network configuration allows telecom installers to save precious time, as there is no need to install optical sockets such as when deploying FTTH infrastructures. Moreover, in the event of a network failure, there is no need to make an appointment for accessing the subscriber’s premises: network can be restored simply by intervening at the optoelectrical node located at the building’s entry level.

 

Along with the FTTH, FTTB is the most reputed and adopted network topology at a global scale. According to an IDATE study, the number of FTTH and FTTB subscribers has increased eight times between 2012 and 2020 in the 28EU countries and the UK. Furthermore, telecoms experts expect these numbers to increase threefold during the period 2020-2026.

 

FTTH and FTTB are the only two network architectures that benefit of a standardised and internationally shared definition by the FTTH Councils of Europe, Africa, Americas, Asia Pacific, Middle East and North Africa. The FTTH Council - the international reference for fibre optic roll-outs - promotes these two network topologies as only solutions capable of delivering the bandwidth and symmetry needed to develop today's societies and economies. Fibre to the Building networks are also environmentally friendly: just like FTTH, the roll-out of FTTB infrastructures can reduce greenhouse gas emissions of up to 88% in comparison with other access technologies.

Ensuring reliable networks from the Optical Distribution to the Building’s Entry Point

 

To ensure future-proof and reliable networks, it is essential to pay particular attention to the connectivity solutions used to roll-out FTTB infrastructures. Quality, scalability and network security are some of the criteria to be considered when selecting the network equipment to be installed. Thus, depending on the area to be served (high-density or low density), two configurations are possible:

 

Overhead layout

Underground layout

An aerial optical cable such as LX030PU can connect an Optical Distribution Point Size 2 (pre-connectorised or for fusion splicing) to another Optical Distribution Point Size 1 mounted on the façade of the building to be connected. Thanks to active equipment, the FTTB network will then be extended up to a dwelling or a business premises via a copper pair or a coax cable already installed.

 

The benefit of this configuration is that, despite the exposed installation, it provides for an increased network security. Indeed, the Eline® Outdoor Optical Distribution Points are developed with a reinforced locking security system: latches plus triangle key or latches and double locking with triangle key for the pre-connected version.

 

Another key advantage is that the use of quality equipment allows the preservation of the optical budget over the entire FTTB network, being able thus to guarantee the fastest speeds to subscribers.

A factory pre-terminated optical cable for underground applications such as the LM4 drop can be plugged into an Optical Distribution Point mounted inside a manhole. Thanks to a structure including swellable yarns, this outdoor FO cable ensures a reliable transmission of the optical signal, even in case of flooding of the manhole.

 

The LM4 cable is designed to run over network segments of up to 70 meters. It will be then used for the opto-electrical transition at the basement or ground floor level of the building to be connected.

 

The key advantage of using a multi-purpose solution such as the LM4 drop cable is that it can adapt both to indoor and outdoor, underground and aerial/ façade applications. Thanks to its dual sheath construction, this cabling solution will enable the anticipation of eventual evolutions of FTTB networks into FTTH: its outer sheath can be removed in just a few seconds and tool-free, giving access to an indoor optical cable.

 

Fibre to the Building networks also present an important scalability dimension. Indeed, if needs in improving the network are identified, telecom players can, at any time, increase the bandwidth, speed or latency performance of their FTTB networks by extending the fibre deployment over the last few meters, all the way to the subscriber’s premises. To transform FTTB networks into FTTH, telecoms installers would then need to extend the existing network by adding a Building Entry Point, a riser cable and Floor Distribution Boxes at each level. These later optical boxes will then be connected to FTTH sockets installed at the subscriber’s premises via indoor optical drops.