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[Weaver]

When FTTP is introduced, what happens to the FTTC services in the area and what happens to the FTTC green cabs? Who needs them when you have FTTP? Would think that maintaining FTTC lines and cabs is just an avoidable expense to BT but I’m not sure about the current economics.

When FTTP is introduced, where is the active and passive optical kit housed physically ? How does the new FTTP kit link in to the existing optical feed that drives the FTTC cabs, if that’s even correct?

[Chrysalis]

I assume as long as the copper network is maintained then FTTC survives, but a point would come (needing ofcoms approval) where the copper will be retired as over time its economic case weakens, LLU is the obvious barrier.

[andew]

In my area since the FTTP hardware was installed nothing has changed with the FTTC hardware at all. If i look at what services are currently available to me,  I get options of FTTP,  FTTC and adsl. I would admit it does seem a bit stupid for BT to have to maintain several different technologies, but not all ISP's offer FTTP services at present,  for example plusnet.

[Black Sheep]

When FTTP is introduced, what happens to the FTTC services in the area and what happens to the FTTC green cabs? Who needs them when you have FTTP? Would think that maintaining FTTC lines and cabs is just an avoidable expense to BT but I’m not sure about the current economics.

When FTTP is introduced, where is the active and passive optical kit housed physically ? How does the new FTTP kit link in to the existing optical feed that drives the FTTC cabs, if that’s even correct?

You're assuming everybody is going to take up FTTP, that simply won't happen. The EU will have a choice of FTTC or FTTP in 'stop sell' Exchange areas. So, the cabs will be around for a good while longer, especially as in some of them, there is actually a Head End (SHE) built into them - GOOGLE 'Subtended Head End'.

Apart from the SHE's mentioned above, all the FTTP equipment is housed in the Parent Exchange. The existing fibre spines feeding the FTTC Cabs usually have spare capacity left at the AGG, so that is where the 'feeds' will be picked up in the first instance. Once the spares have been used up, then a new spine will be pulled in.

All new spines and existing spines begin there journey from the Exchange cable chamber, it is at that point the cross-connections are made to send the various different circuits to the relevant optical equipment, housed all over the damned place and usually on the top floor 

[RealAleMadrid]

For the benefit of others I would add to Black Sheep's comprehensive response with the fact that the equipment in the exchange is the only active powered electronic/optical devices on the FTTP network until you reach the ONT in a user's premises. It is a PON (Passive Optical Network)

Edit: Apart from the uncommon SHE's as already mentioned

[j0hn]

When FTTP is introduced, where is the active and passive optical kit housed physically?

The active kit is all in the Head-End/Handover exchange. The GPON signal comes from an OLT. The FTTC cabinets are also fed by OLT's in the same exchange (sometimes the same OLT).
Everything from here to your ONT is passive equipment.

Fibre goes from the OLT to Aggregation Nodes. The Agg Nodes are underground. The fibre for the FTTC cabinets also goes to these Agg Nodes.
From the Agg Node the fibre then goes to a Splitter Node. Then from the Splitter Node to a CBT (connectorised block terminal). The CBT is the FTTP DP, where your drop cable will come from.

In rare cases, mainly very rural areas, there are SHE's (subtended Head-Ends). Think of them as mini OLT's. They are bolted to the side of a PCP with their power and fibre coming from the PCP's fibre twin.
They are used in places where properties are too far from the exchange for the GPON signal to reach.
SHE's aren't very common.
They may become more common as the FTTP build his more rural areas.

I've attached an image of some of the passive kit I've mentioned.

[Alex Atkin UK]

In my area since the FTTP hardware was installed nothing has changed with the FTTC hardware at all. If i look at what services are currently available to me,  I get options of FTTP,  FTTC and adsl. I would admit it does seem a bit stupid for BT to have to maintain several different technologies, but not all ISP's offer FTTP services at present,  for example plusnet.

It may seem silly on the surface, but consider the cost and hassle of having to run a fibre to every existing customer and swap out their routers, as not all will necessarily have an ethernet WAN port to connect to the ONT.  Who is going to burden the cost of replacing ISP supplied DSL only routers?  Or the cost of the customer having a day off work for the changeover, when they had a perfectly functional broadband connection they were happy with?

There will also inevitably be customers who "don't want an ugly box box on the front of their house", the mess of a new hole being drilled in the wall, their garden dug up, etc.  That last run to the customer can be complicated and messy in itself.

Considering we already have people frustrated when migrating to FTTP because the ONT can't always be placed where the existing phone socket is.  Its just a royal PITA and there's not enough engineers to handle people upgrading to FTTP as it is, probably not enough ONTs either to ramp up any more thanks to the silicon shortage.

[j0hn]

In my area since the FTTP hardware was installed nothing has changed with the FTTC hardware at all. If i look at what services are currently available to me,  I get options of FTTP,  FTTC and adsl. I would admit it does seem a bit stupid for BT to have to maintain several different technologies, but not all ISP's offer FTTP services at present,  for example plusnet.

It's rightly being done in stages.

Openreach set dates for exchanges to "FTTP Priority" exchanges.
Once an FTTP Priority exchange reaches 75% Ultrafast coverage (ultrafast is defined as FTTP + G.Fast above 300Mb/s) then a stop sale is triggered.
Anyone who has access to FTTP will only be able to order FTTP.
Those properties won't be able to do working line takeovers, start of stopped lines, migrations, CP transfers, addition of broadband to copper voice lines, bandwidth modify, or addition of lines and channels to existing installations, for any product other than FTTP.

* I think I might have read somewhere that the 40Mb FTTC product was going to be allowed to continue for a limited time period but can't fit the life of me find that now. I might have imagined that.

They need to do it exchange by exchange like this because providers need to purchase GEA cablelinks in preparation for FTTP and to ensure they have adequate backhaul to offer Ultrafast products.

If they simply made it so anyone who has access to FTTP is only able to buy FTTP as soon as it became available then it would massively limit the choice of provider for anyone who has it deployed early in a rollout before providers were able to have the necessary infrastructure available on their exchange.

Some exchanges only have a couple hundred properties with FTTP (new builds or BDUK funded) and aren't part of any future rollout plan yet. It isn't worth it for the likes of Talktalk or Sky to purchase the expensive cablelinks for FTTP so that would limit the choice of provider for those properties for years to come.

When an exchange has 75% coverage they can be sure it's financially viable for providers to have done the necessary upgrades as there is sufficient customers to take the products. The exchange will have been announced as an FTTP Priority exchange some time before hand giving them time to arrange said upgrades.

[Black Sheep]

In rare cases, mainly very rural areas, there are SHE's (subtended Head-Ends). Think of them as mini OLT's. They are bolted to the side of a PCP with their power and fibre coming from the PCP's fibre twin.
They are used in places where properties are too far from the exchange for the GPON signal to reach.
SHE's aren't very common.
They may become more common as the FTTP build his more rural areas.

Been a massive push on this only last week, j0hn - to ensure that SHE's are used before deploying costly new spine cables, as opposed to only using them for signal issues. So indeed, we will see more of these deployed over the months/years  .

[g3uiss]

I wonder what’s  the value of copper underground 

[gt94sss2]

I wonder if, as FTTP uptake in an area increases, those still on FTTC experience better sync speeds due to less crosstalk?

[Alex Atkin UK]

I wonder if, as FTTP uptake in an area increases, those still on FTTC experience better sync speeds due to less crosstalk?

I was actually wondering if the reason my error rate is so low is not just the repair to the drop cable, but also as Three 5G launched so some people may have moved over to that.

Some people closer to my cabinet are likely also in range of Vodafone 5G, though Three is more appealing as its cheaper than FTTC.

[Weaver]

Thank you all for your generous replies. I’ve just read the Wikipedia article on "OLT" which was as clear as mud; I’d rewrite it if I knew anything about the subject, left me still not understanding exactly what an OLT does. It’s the boundary between the PON and the upstream fibre network, yes? And it’s active.

Can anyone tell me what the detailed protocol stack upstream of the OLT is? I’m certain I’ve asked this question before, so mea culpa and a recap would be appreciated for the optical physical layer case.

[Alex Atkin UK]

This seems a reasonable explanation https://www.fiberopticshare.com/basic-knowledge-optical-line-terminal-olt.html

This also may explain where Openreach speak comes in, based on the number of customers served it looks they seem to be referring to the OLT as a PON rather than the individual PONs that come out of it.  Also the ONU in the diagram appears to be what we refer to as an ONT.

[burakkucat]

Also the ONU in the diagram appears to be what we refer to as an ONT.

ONT and ONU are synonyms.