The physical roll-out of fibre to the premisses

Around where I am (in a "Fibre First' exchange area) I've seen Openreach run new cables and according to the map some streets nearby have gone live for FTTP.

What I've noticed is that OR appear to be doing cul-de-sacs first! Which at first sight appears odd. You'd expect a cable to run up a main-ish road, those properties to be enabled then, as the cable progresses, turn down smaller roads until at the end the dead-end-streets are connected.

I bet someone here can either explain why this is!

Something to do with how the cable from the head-end (?) is split into smaller bundles and the end is an easier place to start?

Without looking at the Openreach duct/pole maps and time planning it hard to say much.

It may be down to age of properties, and they have the pavement chambers needed for kit already in place. Another factor is whether ducted lead in to the property or directly buried, the list of options for not doing what some see as logical continues.

NOTE: Have seen some large areas where the outer edge areas get done first with a long spine cable running to them, and then the shorter cables run in over time for the others between exchange and first spot. One advantage of this method would be you've cleared any duct issues on the longest run so the other subsequent ones might now be easier.

In reply to a post by MrSaffron:

Without looking at the Openreach duct/pole maps and time planning it hard to say much.

Yes, it a 'modern' suburb. Most of the houses will be less than thirty years old, most probably less than twenty with a lot less than five. They all have underground ducts to the houses. Lots have Virgin! There are plenty of chambers in pavements.

The area is almost at the end of the exchange area. A few streets away, right at the end, some streets have been provisioned via poles. Those are 80 - 90 year old properties though.

It does look as if not only are they doing the cul-de-sacs first, they are doing the streets furthest from the exchange first. Oh, except for the streets near the exchange. But maybe they were exchange only properties. Or already have Virgin.

My town is being rolled out currently, they seem to be doing the outside edges and denser areas first, but it does seem slightly random (to my eyes) the order, but I'm sure there's a reason for it. Annoyingly the first area they did, the fibre ran right under my kitchen window to supply the estate at the end of my road. Nothing on my street though 😩 There's also been a CBT on the pole outside my business for weeks, but still can't order. Hang in there!

You may find that each close is run from 1 chamber and may have just the right number of houses for a splitter so 12 or 24. If already ducted these will be nice units to do and easy to release as likely to be one postcode. Whereas the long street will be many postcodes and each chamber may cover non exclusive postcodes and a messier duct layout. It is likely all the fibres have been run along the road already to all the chambers just the fitting and connecting up to be done.

and may have just the right number of houses for a splitter so 12 or 24.

A single splitter would be 32, but then depending on which type of splitter is fitted, additional splitters can be added to their node, so 64, etc.

What dictates the number of properties, is the number of ports on the CBT (connectorised block terminal) so these come in 4, 8, or 12 port varieties. Each port has a single fibre back to the splitter. After the physical splitter/prism there is one fibre back to the head end in the serving exchange.

In reply to a post by Zarjaz:

Each port has a single fibre back to the splitter. After the physical splitter/prism there is one fibre back to the head end in the serving exchange.

"One fibre" back to the head end, is that the same as the "one fibre" which goes into a property? Or is it one fibre with more strands. There must be a limit to the number of final connections that can squeeze down the line.

Its all hard to get my head around....

One fibre is split by wavelength so only some data goes down the street that splitter serves and than its kinda split again at the CBT? Or is that where everyone gets everyone else's data and we hope the ONT filters our neighbours smut out? 😳

I'm hyper sensitive to OR vans at the moment and haven't seen any very close although I did see someone sitting doing something fibre like in a chamber near the FTTC cabinet recently. I have seen big vans running cable down the nearby main road though.

1 single fibre from the exchange to a splitter.
The splitter then splits this single fibre to 32 fibres, 1 for each property.

The exact same data travels down all of the 32 fibres.
Your ONT only decrypts your own data.

Edited by j0hn83 (Mon 13-Jul-20 16:18:12)

In reply to a post by j0hn83:

1 single fibre from the exchange to a splitter.
The splitter then splits this single fibre to 32 fibres, 1 for each property.

The exact same data travels down all of the 32 fibres.
Your ONT only decrypts your own data.

So there is one single fibre per 32 properties running from the head end. If there are 3200 properties there's a bundle of 1000 fibres at the head?

3200 properties is a bundle of 100 fibres.

https://www.thinkbroadband.com/news/8324-openreach-t...

1,728 fibres in a 9.5 mm diameter cable.

In reply to a post by Woolwich:

In reply to a post by j0hn83:

1 single fibre from the exchange to a splitter.
The splitter then splits this single fibre to 32 fibres, 1 for each property.

The exact same data travels down all of the 32 fibres.
Your ONT only decrypts your own data.

So there is one single fibre per 32 properties running from the head end. If there are 3200 properties there's a bundle of 1000 fibres at the head?

Check your calculation ...

3200/32 = 100

In reply to a post by MHC:

Check your calculation ...

3200/32 = 100

Er, sticky "0" on me keyboard.

In reply to a post by MrSaffron:

3200 properties is a bundle of 100 fibres.

https://www.thinkbroadband.com/news/8324-openreach-t...

1,728 fibres in a 9.5 mm diameter cable.

It's quite amazing really to think how much space would be saved in ducts replacing copper with fibre at that type of density level.

I bet Openreach wished they could just pull the copper out and push the fibre back in, as surely this would avoid so many blocked duct and speed up the process considerably for many areas. Oh the hassle of having customers needing a service . Shame someone couldn't devise a machine that would allow a connection for customers at the DP for continuity whilst they rip the copper out.

In reply to a post by kitcat:

You may find that each close is run from 1 chamber and may have just the right number of houses for a splitter

This.

I live at the end of a cul-de-sac with 23 houses. When OR installed FTTPoD, they put a splitter node in the footbox nearest the entry to the cul-de-sac (I talked to the engineers while they were splicing it), and from there a cable to the CBT in the footbox outside my house, passing through other footboxes on its way.

This latter cable was much thinner - I'd say roughly TV-coax sized - so they'll be able to pass other ones through the same ducts later.

Are the splitters put in place first or the cbts, or is it dependent on which teams are available?

In reply to a post by MrSaffron:

3200 properties is a bundle of 100 fibres.

https://www.thinkbroadband.com/news/8324-openreach-t...

1,728 fibres in a 9.5 mm diameter cable.

So that single 9.5mm cable could in theory be used to wire up 55296 homes which if each took 1gbps service that 55,296,000,000,000 1's and 0's per second through that single cable.

And if my understanding is correct that's without doing anything fancy like using higher data rates and multiple wavelengths of light to cram more data down which I believe they can do and that could multiply the data throughput by up to several hundreds of times.

Simply amazing

In reply to a post by StuB:

So that single 9.5mm cable could in theory be used to wire up 55296 homes which if each took 1gbps service that 55,296,000,000,000 1's and 0's per second through that single cable.

Not exactly. With today's GPON, that "1gbps" service is contended: everyone on the same fibre gets 2.4G down and 1.2G up (shared). So your 1,728 fibres are used to deliver 1728*2.4G = 4.147 Tbps downstream.

Not that a small town of 55,000 homes uses anything like that amount of bandwidth currently.

However as you then observe:

In reply to a post by StuB:

And if my understanding is correct that's without doing anything fancy like using higher data rates and multiple wavelengths of light to cram more data down which I believe they can do and that could multiply the data throughput by up to several hundreds of times.

Exactly. When there's enough demand, they can switch to one of the 10G versions of GPON, or in future 40G, or 100G... just by changing the optics at each end. Single-mode fibre is indeed amazing.

. Shame someone couldn't devise a machine that would allow a connection for customers at the DP for continuity whilst they rip the copper out.

They have - mobile phones.

In reply to a post by candlerb:

Not exactly. With today's GPON, that "1gbps" service is contended: everyone on the same fibre gets 2.4G down and 1.2G up (shared). So your 1,728 fibres are used to deliver 1728*2.4G = 4.147 Tbps downstream.

Not that a small town of 55,000 homes uses anything like that amount of bandwidth currently.

Thanks for clarifying that.

So with the BT Full Fibre packages they guarantee a download speed which if multiple people on the same, shared fibre took could be way above the 2.4gbps that the fibre can carry.

In the real world I guess this is unlikely to be an issue as you're very unlikely to have everyone on a shared fibre fully utilizing their connection at the same time.

Has contention ever become an issue for fttp yet?

I bet Openreach wished they could just pull the copper out and push the fibre back in, as surely this would avoid so many blocked duct and speed up the process considerably for many areas. Oh the hassle of having customers needing a service . Shame someone couldn't devise a machine that would allow a connection for customers at the DP for continuity whilst they rip the copper out.

Indeed - one of the many reasons why Openreach is desperate to shut down the PSTN. Once that has gone and we are all on at least SOGEA FTTC, the copper from cabinet to the exchange is redundant.

In reply to a post by Nick_W789:

Indeed - one of the many reasons why Openreach is desperate to shut down the PSTN. Once that has gone and we are all on at least SOGEA FTTC, the copper from cabinet to the exchange is redundant.

So will they leave it in the ground or pull it out? Does the scrap value make it worth doing?

In reply to a post by Nick_W789:

Indeed - one of the many reasons why Openreach is desperate to shut down the PSTN. Once that has gone and we are all on at least SOGEA FTTC, the copper from cabinet to the exchange is redundant.

It isn't redundant on SOGEA yet.

The E-Side is still physically connected on all SOGEA lines so that ISP's can perform some line tests.

There's also products like SOTAP that have been developed for the PSTN switch off.

The PSTN switch off doesn't mean the end of E-Side cables. It just means the end of PSTN.

There can't be any E-Side recovery until there's full coverage of FTTC or FTTP.

They can’t, they need Ofcom’s permission to rip out the copper and force people onto fibre unfortunately. If BT still had the monopoly that wouldn’t be the case. Problem is now that the likes of Sky have their DSLAMs in the exchange, copper is being used for that.

Regarding the Fibre Cities rollout, my observation round here (knowing what I know about the network) is that they’re targeting high fault areas first. That makes a lot of sense to me. Of course that won’t be the case with every Fibre Cities/ Fibre First rollout but without a doubt that’s what I’m seeing here and Openreach managers have confirmed it.

So will they leave it in the ground or pull it out? Does the scrap value make it worth doing?

Damn straight it does.

That’s why others are so keen to do just that before Openreach have finished with it.

They are heading towards a world of just GEA - FTTP, SOGfast and FTTC. SOTAP notwithstanding - T is for transitional. And I can’t see all that valuable copper, not to mention racks and racks of equipment filling exchanges, being left in place just for line tests.

It won't be left in place for line tests, no.
The DSLAM's are technically capable of these, and I believe some of the tests are DSLAM based already.

ADSL will still be a thing in 2025.
Until there's full GEA coverage and agreement with LLU operators (or forcing it upon them) to decommission all their exchange based MSAN/DSLAM's then E-Sides will remain.

Just pointing out that PSTN switch off isn't the end of E-Side lines like your post suggested.
There's a few more years after 2025 till that can/will happen.

The BT 900 service has a 455 Mbps guarantee, and that only triggers a small refund. So nothing like the guarantee you would get from a 1 Gbps leased line

Contention if seen is likely to be transitory i.e. short duration.

That makes sense.

I am sure i read that the cost of scrap copper is a not insignificant part of FTTP costing in . When some E side cable is as thick as your arm and a few Ks long the scrap value must be huge.So yes very much worth pulling out .

Ps is any low life is reading this foxtort oscar as a 4x4 will not work !

No hard and fast rules

Guardian did the sums some years ago but got them wrong.

The price of copper is a big driver, and likely that will go down as lots of telco start to scrap copper around globe

In reply to a post by MrSaffron:

Guardian did the sums some years ago but got them wrong.

The price of copper is a big driver, and likely that will go down as lots of telco start to scrap copper around globe

Or up, as more people buy electric cars containing ~90kg of copper each, versus 10-25kg in a conventional vehicle.