FTTP Contended Bandwidth

Just been talking to an Openreach surveyor, they are currently preparing for FTTP in our area.

My distribution point is under ground and serves 4 properties.

I was wondering is the 1 gig back haul connection shared between the 4 properties on my DP or is it also shared between multiple DP's?

The PON (Passive Optical Network) is shared with up to 30 (technically 32) ONT devices on the Openreach network. For the vast majority, these will be single subscriber, single-port ONT devices, rather than 4-port ONT devices.

The PON bandwidth for GPON which is the current technology that Openreach deploy is 2.488 Gbps down stream and 1.244 Gbps in the upstream. These are the raw figures on the 'optical side' of the network. An individual subscriber connection on its ethernet connection can have up to 1000/220 Mbps (down and up).

Contention of the PON is quite tightly controlled using various means, I can link you to the SIN technical note for GEA-FTTP if you have trouble sleeping. The upshot is that you should never, ever really see any worse in practice than 50% of your headline rate.

I say worst case, as most folks will typically get their nominal headline speed, pretty much consistently day or night.

Thanks for the info

So is the PON likely to sit where the current DP is (serving 4 properties) or can these be a little deeper into the network serving properties that are currently connected to multiple DP points?

So the “PON” is the entire optical fibre network segment, originating from the optical port on the OLT at the exchange and includes the said up to 30 / 32 active devices at user premises.

The network is all passive once it leaves the exchange; after the aggregation node the fibre goes to a splitter node where the light is passively split up to 32 ways. Several DP’s (or connectorised block terminals - CBTs - those black nippled boxes on the tops of poles or in underground chambers) will be fed from a splitter node. Sometimes the fibre from a splitter node will be through spliced at a subsequent track node on the way to the final CBT. Splitter nodes have several 32-way PON splits (cassettes inserts on fibre trays) inside them, arranged as primary, secondary, etc etc. each of which feeds 32 onwards end connections.

Seems like you are hoping that you will only be sharing your network with just the 4 properties? You'll be lucky

Your DP goes back to a splitter where other incoming fibres from other DPs arrive, so you are very likely to be sharing with many more households. Whether that is 10, 20 or 30 is impossible to say as a lot depends on Openreach and how the network is organised in the area, and the information isn't public to find out.

You are far more likely though to meet congestion and get slower speeds from bottlenecks elsewhere.

In the future the speeds can be upgraded by just changing the kit at each end, as the fibre itself can easily carry more data. The next step up when deployed will see the fibre optic cable carrying 10G symmetrically on top of the 2.4/1.2 of current GPON, i.e. they can both work concurrently on the same fibre.

Edited by E300 (Fri 24-Sep-21 16:12:00)

Ripley

In addition to the other answers telling you it will be shared between up to 32 connections, you need to remember that at present not everybody will take FTTP to start with. So there may be 32 possible connections but it is unlikely that they will all be working for some years, ( Maybe until the copper is recovered) . In a rural area with poor FTTC or ADSL take-up is likely to be higher than in an urban area with 60Mb+ FTTC already, but even there there are people without BB or who are happy with sub-8Mb service. .

In reply to a post by kitcat:

Ripley

In addition to the other answers telling you it will be shared between up to 32 connections, you need to remember that at present not everybody will take FTTP to start with. So there may be 32 possible connections but it is unlikely that they will all be working for some years, ( Maybe until the copper is recovered) . In a rural area with poor FTTC or ADSL take-up is likely to be higher than in an urban area with 60Mb+ FTTC already, but even there there are people without BB or who are happy with sub-8Mb service. .

Quite so, and unless all of ones neighbours are hardened bit-torrent and multi 24x7 4K UHD streaming junkies, I would expect the "bell curve" distribution of subscriber bandwidth profiles to mirror what's widely seen on FTTC...a majority of folks clustered towards the lower tier profiles, rather than the higher tier profiles.

A good number may end up simply being used for 0.5 Mbps over the top voice connections when copper finally goes.

Hi Pheasant,

Thanks for the detailed information, I was just interested to understand how it works more than anything and that is a great explanation below.

You're welcome

This is probably rare, but in lower housing density areas you may see less than 30 subscribers per splitter.

I know for a fact the splitter I am on only has 17 CBT ports spliced, this is also in a Virgin Media area so assuming about 33% take VM over an OR FTTP service I reckon the max users will be about 12 when copper services are withdrawn