Which optical fibre distribution box to choose?
Already available in many urban areas but also in some rural zones, the optical fibre network is more and more deployed in the UK. For detached houses, the local fibre network ends in front of the premises. It all starts with the telecom manhole, where we can find the copper telephone wires, the ADSL and/or fibre optic cables. This is where you can find the Optical Distribution Point, whether installed in overhead or underground layouts.
In the case of an underground installation, telecom field engineers use duct rods for pulling applications in order to lay fibre optic which will be spliced at the Optical Distribution Point’s level. Following that, an optical telecommunications outlet will be set up in the single dwelling to connect the optical fibre with the use of a splicing application.
For enabling access within dwellings by performing a fibre optic rollout in overhead layout, telecom field engineers use the Optical Distribution Point located on a telegraph or utility pole to route the optical signal up to an outdoor/indoor transition point mounted on the house’s wall.
In the following section we will see the different optical distribution boxes enabling the subscriber to be connected to the ultrafast broadband networks.
ODP: what is an Optical Distribution Point?
A is a white closure used to connect the optical distribution cable to the drop cable(s) directly linked to the outdoor/indoor transition box. The ODP is generally located on the ground floor or in the basement of buildings counting more than several storeys. This optical distribution box is also often mounted in outside plant configurations in suburbs or rural areas, in overhead or underground layouts, according to the chosen rollout method.
This box is used in one of the last stages of enabling subscriber connection(s). It makes the connection between the building entry point and the optical telecommunications outlet (OTO), also called customer terminal box (CTB).
Upstream the fibre network, the Shared Access Point is an end point for one or several optical lines owned by an incumbent who gives access to these very high-speed communication lines to ISPs. This Shared Access Point is directly linked to an access node (also known as Point of Presence or Central Office), which is the concentration point of an optical network and where the active and passive equipment is set up.
Downstream, an intermediate distribution point enables the connection of several subscribers to the full fibre networks, generally of 3 to 12 homes. Intermediate distribution points can be located at different places: at the storey level, on façade, at the underground level or on pole. The chosen connectivity method depends on the dwelling type (SDU or MDU) and its vicinity with the Shared Access Point. In case of connecting MDUs, the connection is performed either at the storey level or on underground.
For single dwellings, the intermediate distribution point is often located on underground or in an overhead configuration.
| Connectivity point | Optical intermediate distribution point | Cable routing |
| Storey level | At building’s landing level | Split corrugated flexible tubing Cable channel Apparent cable laying |
| Underground | In a telecom manhole | Outside + inside split corrugated flexible tubing Cable channel Apparent cable laying |
| On facade | On the front wall of the dwelling | Facade + cable channel Apparent cable laying |
| Underground | In a telecom manhole | Outside + inside split corrugated flexible tubing Cable channel Apparent cable laying |
Optical intermediate distribution point connected to a riser vertical cable
In a scenario specific to multi dwelling units, the intermediate optical distribution point is directly linked to the Building Entry Point. This optical box is mounted at the ground floor or in the basement, and used to connect the different floor distribution boxes placed at each storey level. For that, we use small-diameter fibre cables in order to push them into ducts or already occupied split corrugated flexible tubing.
Optical intermediate distribution point on underground
An optical intermediate distribution point is placed underground in a telecommunications manhole located under the pavement. Then, thanks to cable pulling applications, the fibre optic drop is going to be routed up to an outdoor/indoor transition point enabling to access the dwelling. Further after, the optical signal will be carried up to the OTO.
Optical intermediate distribution point on facade
A facade installation is mostly used for single dwellings, as these last ones seldom benefit of an adequate underground infrastructure. To place an An optical intermediate distribution point (ODP) on the front wall of a house, whenever this last one is placed in the vicinity of a public road, you must respect height regulations:
- New overhead customer connections should be installed at a height of above 5.9m OR 5.6m depending on cable type
- Existing wires should be re-tensioned to 5.5m
Optical intermediate distribution point on overhead
In this scenario, the fibre-optic connection is at the top of a telegraph or utility pole, above the already installed copper network. The ODP is thus mounted at the pole’s top and links the Central Distribution Point (Street Cabinet, splitter node, …) to an OTO which takes the shape of a circuit breaker, installed inside a residential gateway. In this case, the optical signal arriving into this specific OTO is further routed to a FTTH terminal outlet. A second scenario consists into routing the optical signal directly from the ODP to the OTO.
In case of overhead layouts, fibre cables have to meet specific requirements to be resistant to weather conditions such as wind, hail, frost etc.
OTO: what is an optical telecommunications outlet?
The optical telecommunications outlet is a FTTH terminal box. It is a small white box that you will find wall-mounted in the room of your choice. This optical outlet is used to link the ODP to the Internet box: the fiber drop cable is connected to the OTO and then exits the OTO to finally end into the Internet modem. The installation of the OTO is performed during the last mile access connectivity phase.
The different types of fibre terminal boxes OTO
You can find several models of OTO on the market: pre-wired, pre-terminated, with adaptors and pigtails etc. Among those models, there are two types of boxes: the multi-fibre OTO and the mono-fibre OTO.
The multi-fibre OTO generally has 2 or 4 connector ports. Thus, you can simultaneously connect 2 or 4 fibre drop cables coming from the Building Entry Point. Thanks to this fibre optic box, telecom field engineers don’t have to go to the Entry Point to change a cable connection, they can directly do the change from the OTO. In addition, if the subscriber decides to choose another ISP, the field engineer can then use one of the pending fibres.
The mono-fibre OTO is equipped with only one fibre, pulled from the Building Entry Point. The installation is simpler, the fibre capacity slightly optimised, but in case the subscriber wants to change the operator, telecom field engineers have to carry out a more extensive intervention to enable the