Hey WWWombat

When I was referring to speeds, I was referring to the actual speeds that BT use down each strand.

It seems I was about right for the speed for the strands used for FTTC of 1Gbps.

TBH isn't 2.5Gbps downstream a bit low for FTTP?
I thought it would at least be 5Gbps up to 10Gbps.

I know the fibre cables that we have linking all our FibreDP hardware are all using 96 strands of fibre, they were 48 strands, but throughout July last year they replaced those cables for what they had on that huge fibre drum which was 96 strands.
They told me it make no difference if its only connected to a 48 strand the other end, which makes sense.

I am a bit confused, so your saying to supply say 18,175 connections would need 18,175 strands leaving the exchange, that would require 64 cables with 288 strands in each.

And I read some place that each home gets 4 strands of fibre where 2 or 3 are spare., so that would mean 4 times that.

Your saying that an aggregation node extracts 48 to 60 strands and that an aggregation node will support up to 1500 premises, so for that to happen it will have to splice off each of those strands to 25 to 32 smaller strands.

Or am I missing something here?

Paul

splice off each of those strands to 25 to 32 smaller strands

Paul I think you should use the correct terminology.....split not splice....you can only splice 1 to 1 .....

Reading the page that www pointed to...a single fibre can be split to into 32 fibres http://www.fiber-optic-tutorial.com/tag/optical-spli...

Surely there is no such thing as a fibre cable, There is a fibre duct (black with yellow stripe) and then this contains several sub-ducts that contain the actual fibre.

Paul

WWWombat went through it all well. You missed the Splitters in his write up.. Each strand leaving the exchange goes to a primary splitter that splits it to 4, 8, 16 or 32 fibres out the other end of the splitter. A secondary splitter can also be used.

My recollection was a max of 128 premises passed per 2.5Gb ( giving min uncontended 19.5Mb). WWWombat thinks only 32 ( giving min uncontended 78Mb). As not all customers will take the service up or will only take the lower speeds it is more likely to be 128.

There were ( are?) plans to increase this to 256 premises but this will be 10Gb ( giving min 39Mb uncontended).

The linked diagrams are not very clear.

Ian

Look at WWWombats IWCS link there are pictures of the cables.

A large cable will have 288 fibres in it ( could be 360 fibres with some cables)

Each cable will be pulled or blown for smaller ones through the duct.

Nobody ever uses 1 fibre down a subduct. Blown fibe is normally a 4 fibre cable or 8 fibres.

The black and yellow cables are not duct these would be far larger and can have many cables in.

In reply to a post by ian007jen:

splice off each of those strands to 25 to 32 smaller strands

Paul I think you should use the correct terminology.....split not splice....you can only splice 1 to 1 .....

Yeah, sorry I was yapping to somebody here while posting.

In reply to a post by ian007jen:

Reading the page that www pointed to...a single fibre can be split to into 32 fibres http://www.fiber-optic-tutorial.com/tag/optical-spli...

Yeah, it was where WWWombat said

That's a lot of splices, but they're always 1 fibre strand to one fibre strand.

Thats where I got confused

But reading that PDF WWWobat linked to, I can see more.

Going by the images I see...
The Aggregation Node id fed a fibre cable of 200 odd strands and only splices off the 48 that it needs and passes through the rest to go onto the next Aggregation Node and so on.

And those 48 strands goes to a splitter that splices off 4 strands and passes through the rest that goes to the next splitter and so on.

Now each of these 4 strands gets split up into 32 strands giving about 128 strands that go to the FibreDP where it splices off < 20 strands and passes the rest to the next FibreDP and so on.

Is that right.

In reply to a post by ian007jen:

Surely there is no such thing as a fibre cable, There is a fibre duct (black with yellow stripe) and then this contains several sub-ducts that contain the actual fibre.

Ermm, I think there is, I recall throughout July 2015 then replacing the fibre cable that run between all our FibreDP harware, they replced the original 48 stands with a 96 srtand cable and that was all spliced and joint up after they replaced the cables.
So they didn't replace any ducts and blew the fibres.

Ah, I think I know what you mean now, the 96 strand fibre cable is labelled as Subduct - 14 x 10mm, but does that come with all the fibre strands in? due to I didn't see them blow any fibres in and the splicer/jointer guy was sitting on the edge of the chamber with the FibreDP hardware folded up on its arm and he was doing stuff with the wafers.

Paul

but does that come with all the fibre strands in?

No......I'm sure Mr S has said before all fibres are blown in after the subduct is pulled; they are much to fragile to be inside whilst the subduct is installed.

In reply to a post by kitcat:

Paul

WWWombat went through it all well. You missed the Splitters in his write up.. Each strand leaving the exchange goes to a primary splitter that splits it to 4, 8, 16 or 32 fibres out the other end of the splitter. A secondary splitter can also be used.

Yeah, the phone rang and I lost concentration, I knew it split up the fibres, I just wasn't too sure if it split any in the Aggregation Node.
So in theory each 288 strand fibre cable (COF 200 Cable) will get split into about 9,216 strands.

In reply to a post by kitcat:

My recollection was a max of 128 premises passed per 2.5Gb ( giving min uncontended 19.5Mb). WWWombat thinks only 32 ( giving min uncontended 78Mb). As not all customers will take the service up or will only take the lower speeds it is more likely to be 128.

That to me doesn't seem right to me, if everyone i.e. FTTC and FTTP users are all the same as that then the FTTP users are being shafted and ripped off.
Are you sure its 2.5Gbps for both FTTC and FTTP Customers?

Nope your right, it seems that its 2.5Gbps downstream and 1.2Gbps upstream, still doesn't see right to me.
That 2.5Gbps according to the docs that was linked say its gets split by 32, and where 4 strands go into the splitter resulting in 4 x 32 is 128 homes, so its 128 homes over 4 strands, that's my understanding (read it 4 times now LOL).

In reply to a post by kitcat:

There were ( are?) plans to increase this to 256 premises but this will be 10Gb ( giving min 39Mb uncontended).

I did read some place on the BT or openreach page that BT are working on 40Gbp over a single strand, Denmark has working 43Tbps over a single strand [shock]

In reply to a post by kitcat:

The linked diagrams are not very clear.

Yeah, doesn't really halp when they don't say what some of the names they use, like SASA, SPN, EU etc.

Paul

In reply to a post by ian007jen:

but does that come with all the fibre strands in?

No......I'm sure Mr S has said before all fibres are blown in after the subduct is pulled; they are much to fragile to be inside whilst the subduct is installed.

Well when I asked them will they be blowing in the fibre once the tubing has been installed and the exact words from the fibre engineers was "there is no need to blow any fibre in on these shot distances" and that the cables they was putting in already had the fibre strands in.

So I am only going by what I was told, and for the splicer/jointer guy did hid part not long after they put the cables in confirms this.

Paul

The cables that they replaced between all our FibreDP hardware was black with the yellow strip, but was a lot thinner that the tubing that goes up the phone pole, looking at that BT Doc it looks like the 96 core subduct cable (14 x 10mm), I say 96 due to that's what the guys said that installed.


When you say "Blown fibre is normally a 4 fibre cable or 8 fibres" is that why FTTP gets 4 fibre blown to their external termination box, like 3 spare ones for future use or redundancy?

Paul

This type does exist - and is part of the changes to try and reduce work load but mainly in the FoD2 and G.fast trials for now