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Standard User PaulKirby
(fountain of knowledge) Fri 26-Feb-16 22:00:39
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Splicing fibres and speed questions...


[link to this post]
 
I am just wondering how long on average does it take a BT Fibre Splicer Engineer to splice/join a strand of fibre?

Also I recall a little while back we was discussing actual speeds down a single strand of fibre, I don't recall getting a definite answer.

Also not really knowing how many fibres get spliced from a strand of fibre.
So say a fibre cable leaving an exchange consists of 48 strands, I assume that will get spliced as it runs down the road, but to what amount of fibres get spliced from one of the 48 fibre strands?

I worked out the following which I am positive I am completely wrong and I am happy to be corrected.

My understanding was a fibre strand that is to be used for FTTP has a bandwidth of 10Gbps and each strand gets spliced off into 30 smaller ones.

Where as a fibre strand for FTTC has a bandwidth of 1Gbps that gets split up into 15 smaller strands.

And where exactly does the fibres get spliced for FTTP, is it as it goes down the road from the exchange to the first daisy chained FibreDP hardware.

Or does it only get spliced in the actual FibreDP hardware where 1 ro 2 strands are spliced into 15 strands on each resulting into 30 lines for 30 addresses on the same phone pole.

I am aware they would need to install extra tubing's for more addresses.

The main reason that I am asking these questions are due to BT have had work outside our exchange on roadworks since January stating
Safe Access to Underground BT footway and carriageway boxes for fibre cabling and jointing works in existing duct. Required for new customer connection

Now that work never happened due to they required some lanes to be closed for safety reasons, which I can understand.

Then then rescheduled that work 1 month later i.e. 23 Feb - 24 Feb with lane closures.

I just noticed on roadworks today that they have two lots of work down as the following.
  1. Safe Access to Underground BT footway and carriageway boxes for fibre cabling and jointing works in existing duct.
    Required for new customer connection we did not finish all the work last time we where there that is why we need to rebook it
  2. Safe Access to Underground BT footway and carriageway boxes for fibre cabling and jointing works in existing duct.
    Required for new customer connection we did not finish all the work off last time we where there so that is why we need to go back there

Basically the same thing, but it seems that the tile allocated for 23 to 24 wasn't long enough, so I am assuming that there must be a lot of jointing work to be done if they could do it in that allocated time.

We have been told by BT that they are looking into our FTTP issue that has been delayed for 50 months now, and BTOR has told me the work will be completed end of Feb then up-to a further 2 weeks for the database to get updated and then activated.
We have around 18,175 FTTP lines partly done leaving 12,303 FTTP lines including the ~400 line in our area.

Our area is hoping its for us and the remaining FTTP connections.

My guesses are our fibre has already been blow due to they spliced our fibres in the FibreDP hardware end of July 2015, so I am thinking that they are just joining them up at our exchange end.

I was told by many different BT Fibre Engineers that there was a big chunk of our fibres got damaged back end of 2011 and that FTTP fibres come form a different place or cable or node that FTTC does which was why the FTTC got all done leaving the FTTP partly completed, now whether those engineers were correct or not I cannot say, but that would explain why every engineer that looks in the chamber by our phone pole all say its done.

Thanks

Paul
Standard User Zarjaz
(eat-sleep-adslguide) Fri 26-Feb-16 22:34:40
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Re: Splicing fibres and speed questions...


[re: PaulKirby] [link to this post]
 
I am just wondering how long on average does it take a BT Fibre Splicer Engineer to splice/join a strand of fibre?

Lots of variables to take into account, but once all set up OK, strip/cleave/clean/splice, a couple of minutes.

Standard User Zarjaz
(eat-sleep-adslguide) Fri 26-Feb-16 22:44:09
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Re: Splicing fibres and speed questions...


[re: Zarjaz] [link to this post]
 
https://www.youtube.com/watch?v=kfYNj3nIPV8

..but the old guy looks a little slow to me ....

.. nice to have it all laid out on a table ..


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Standard User PaulKirby
(fountain of knowledge) Fri 26-Feb-16 22:50:07
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Re: Splicing fibres and speed questions...


[re: Zarjaz] [link to this post]
 
In reply to a post by Zarjaz:
I am just wondering how long on average does it take a BT Fibre Splicer Engineer to splice/join a strand of fibre?

Lots of variables to take into account, but once all set up OK, strip/cleave/clean/splice, a couple of minutes.
Ah, so my guess of 2 mins was about right ,I know there is a machine that thermally joins the fibres, which is a lot better than what we used 20 years ago LOL all we had was an eye lens a knife, very fine grit stone and what looked like washing up liquid which was used to polish the fibre ends where we then had a section that had glue in it and we pushed the two end into that LOL.

Do you know answers to any of the other questions ?

Paul
Standard User partial
(experienced) Fri 26-Feb-16 22:56:21
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Re: Splicing fibres and speed questions...


[re: PaulKirby] [link to this post]
 
Jointing 48 fibres and closing them is pretty quick work. The delay will be down to traffic management, cars parked on boxes and cabling problems such as blocked ducts etc.

Jointing 4800 copper pairs and closing them, long time.
Standard User PaulKirby
(fountain of knowledge) Fri 26-Feb-16 23:01:09
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Re: Splicing fibres and speed questions...


[re: Zarjaz] [link to this post]
 
In reply to a post by Zarjaz:
https://www.youtube.com/watch?v=kfYNj3nIPV8

..but the old guy looks a little slow to me ....

.. nice to have it all laid out on a table ..
Yeah, that's what I am saying, we never had all that to do it for us 20 years ago LOL

So easy nowadays tongue

Also that last part with the shrinking part, that didn't look like it was done due to it was the same size, heat shrinkable tubing I use all the time and they normally always shrink in diameter, like 3:1 or 2:1, I have also worked with a 5:1 tubing when I have had to cram loads of copper wires through them.

Paul
Standard User PaulKirby
(fountain of knowledge) Fri 26-Feb-16 23:31:33
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Re: Splicing fibres and speed questions...


[re: partial] [link to this post]
 
In reply to a post by partial:
Jointing 48 fibres and closing them is pretty quick work. The delay will be down to traffic management, cars parked on boxes and cabling problems such as blocked ducts etc.

Jointing 4800 copper pairs and closing them, long time.
Ah, well I did some maths LOL.

Still not fully sure on how many strands gets spliced off each of those 48 strands, like I said I am probably wrong when I say each strands gets spliced into 30 strands.

If that is correct and we only require another 12,303 FTTP to be completed, so that would be about 9 lots of fibre cables with 48 strands in them, and 7 cables would be all used up and would also use up 17 strands of the 9th cable, or maybe they will spread them across all of them.

That is assuming I am right and that this work is for us, but 2 days wasn't enough time so it must of been a lot of work to do to request for another 2 days to complete the rest.

Well I am just assuming here, but I am thinking that where there was loads of talk about broken fibre cables back end of 2011, I was thinking that the actual break was in between those two chambers and that they would just need to cut the broken fibre cables in each chambers and then pull them out and replace those removed with new cables and then re-join those back up in both chambers and that's it.

I am aware its a main road that there is a lane closure, but doesn't stop a car from hitting you tongue

I am also not sure if the work is for both sides of the road, so yeah, that becomes more of an issue and delays, but it looks like the chambers are on either side of the road.

The nearest postcode to it is IG1 2FB and select 2 weeks or longer and you will see the two jobs pop up.

Paul
Standard User WWWombat
(knowledge is power) Sat 27-Feb-16 11:36:36
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Re: Splicing fibres and speed questions...


[re: PaulKirby] [link to this post]
 
I feel a long post coming on...

In reply to a post by PaulKirby:
I am just wondering how long on average does it take a BT Fibre Splicer Engineer to splice/join a strand of fibre?


Another video, courtesy B4RN.
https://www.youtube.com/watch?v=PpjVHpYHFQA

A mix of stills and video, but useful part is around 5 mins in.

In reply to a post by PaulKirby:
Also I recall a little while back we was discussing actual speeds down a single strand of fibre, I don't recall getting a definite answer.


How long is a piece of string?

Minimum speed probably around 100Mbps. Maximum speed achieved in a trial between Huawei and BT in 2014 was 3Tbps. But achieving that required a "grid" of wavelengths on the same fibre: 15 wavelengths of 200Gbps each. That is backed by serious transmission hardware.

For the access network, they need cheaper hardware at each end of the fibre.

The GPON system BT are trying desperately to put in your street is 2.5Gbps downstream, 1Gbps upstream, shared. With a distance limitation of around 20km.

The fibre network being deployed is quite capable of carry 10G-PON signals too, which is 10Gbps downstream, all to be shared.

Those speeds are more limited by the hardware they put at each end of the fibre than on the fibre itself.

Meanwhile, the fibres used for FTTC carry a point-to-point connection running at 1Gbps. They too could be upgraded to higher speed PtP connections in the future, depending on the hardware in the OLT and the DSLAM.

Standardised speeds, cheap-to-achieve, suitable for 1 wavelength on a fibre in the access network seem to be 100Mbps, 1Gbps, 10Gbps. With perhaps 25Gbps coming.

In reply to a post by PaulKirby:
Also not really knowing how many fibres get spliced from a strand of fibre.
So say a fibre cable leaving an exchange consists of 48 strands, I assume that will get spliced as it runs down the road, but to what amount of fibres get spliced from one of the 48 fibre strands?


One fibre will be spliced to one fibre. No question about that.

When you see B4RN's video, watch the screen showing the two fibres being spliced ... there is no room to branch the connection there.

In reply to a post by PaulKirby:
My understanding was a fibre strand that is to be used for FTTP has a bandwidth of 10Gbps and each strand gets spliced off into 30 smaller ones.

Where as a fibre strand for FTTC has a bandwidth of 1Gbps that gets split up into 15 smaller strands.


The fibre strand that exits the exchange, identical for FTTP and FTTC, will be one strand within a cable of up to 288 - but usually in groups of 12 strands known as an element.

Where one fibre (at the exchange end) is used to serve multiple homes in an FTTP GPON, the division isn't done by "splicing off 30 smaller ones". It is done by splicing that single fibre to one end of a "splitter device". That device will have 4, 8, 16 or 32 fibres at the other end - all ready to be spliced onto by the fibres strands that (eventually) make it to your house.

The splitter devices appear to be passive silicon wave-guide devices.
http://www.fiber-optic-tutorial.com/tag/optical-spli...

At first, BT seemed to be set on using a single level of splitter: one 32-way splitter device. This would be housed within a "splitter node" which had room for 4 devices, so could serve 128 properties, all from 4 fibres back to the exchange. Towards the homes, there would be a final splice at a fibre DP - where the fibre strands would change from being within a cable alongside other subscribers, to a fibre blown down a BFT that is exclusively for your house.

Nowadays, BT seem to be planning for two levels of split: The first level would be an 8-way primary splitter, and the second level would have 8 four-way secondary splitters. It still amounts to one fibre in, 32 homes served.

The 8-way splitter looks likely to be housed alongside 3 others in a smaller splitter node, while the 4-way splitter might be housed underground, in a pole-mounted housing or even at the top of the pole (in the new FoD2-style of connectorisation). In this 2-level setup, the secondary splitter is likely to act as a DP too.

The fibre for FTTC doesn't go through a splitter device at all. It is spliced 1:1 through the aggregation node to a port on the FTTC cabinet.

And where exactly does the fibres get spliced for FTTP, is it as it goes down the road from the exchange to the first daisy chained FibreDP hardware.

Or does it only get spliced in the actual FibreDP hardware where 1 ro 2 strands are spliced into 15 strands on each resulting into 30 lines for 30 addresses on the same phone pole.


There are lots of places that splices happen, for a multitude of purposes.

First, take a look at some example architectures for FTTP.
This PDF includes BT's thoughts for the whole access network circa 2010:
IWCS presentation 2010

This image is of a considerably more modern look
Two-level of split FTTP

Finally, you can also see some details of the architectural changes for FoD2:
TBB Blog on FoD2

Here's how the architecture boils down to a set of splices...

Stage 1 - Out of the building
1. The FTTP fibre starts as a connector plugged into a GPON port on the OLT.
2. The first splice is within the OCR (Optical consolidation rack), where it starts to joining up with all the other strands heading to the same area of town.
3. The yellow cables from the OCR are probably internal grade (low smoke). They will be spliced to external-grade cables down in the "cable chamber" in the basement - A "CCJ" (cable chamber joint?)
4. The cable leaving the exchange, via the chamber, will be up to 288 strands of fibre, and will form one of the fibre spines snaking out of the exchange to an area of the town.

Stage 2 - Fibre Spine
5. When the cable gets to the first area to service, it will go into an aggregation node. Here , perhaps some 48-60 of the fibres will be extracted from the spine, and "laid up" in splice trays for future use. The remainder will pass straight through unspliced to the next aggregation node in the daisy-chain.
6. Each aggregation node is a "flexibility point" like today's PCP, in that this is one of the main locations for swapping connections in the case of failures or breakages. It will support up to 1500 premises, so is perhaps equivalent to 2-4 PCP's in scale.
7. A fibre spine that starts as 288 fibres might drop 48-60 of them at each aggregation node. That might make for 5 large aggregation nodes along one spine, or more smaller ones.
8. Each fibre cable is of a limited length, so might not be able to run the complete distance between exchange and aggregation node. If so, extra "TJ"s will be inserted, complete with splices, so a new section of cable can be run. Track Joints? or Transit Joints?
9. The fibre spine is the equivalent to today's E-side cables. The fibre from the aggregation nodes towards the premises is the distribution fibre, equivalent to the D-side.

FTTC areas will only have the architecture above. FTTP areas will continue with the next level.

Stage3 - Distribution Fibre
10. The first step of the distribution fibre is to be routed to a tray in the aggregation node, and spliced to one of the spine fibres. The cable will then be fed through ducts into a splitter node. I guess that these cables are likely to have 36, 48 or 96 fibres.
11. In the example 2-level architecture, the distribution fibre will then, for example, be sent to one of the 8-way splitter nodes - where it will be located in a splice tray, and spliced to the input to the splitter device.
12. The output from the splitter device will then be located in another tray, and spliced to the fibre strand that is heading further in your direction. This fibre will be in another cable, fed through ducts towards the house.
13. This fibre will enter the 2nd-level splitter, and again put into a tray where it will be spliced to the input to the splitter device.
14. The output from the splitter will be routed into a separate tray, where it will be spliced onto another strand of fibre heading in your direction. If this secondary splitter forms the job of a DP too, then this strand will be the final strand of fibre destined for your house.
15. The final strand is likely to be fibre for blowing in BFT over to your house. Once it arrives, it will be put into the splice tray located on the outside of your property. Here it will be spliced onto cable suitable for running inside your house.

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

There are some pictures and descriptions of the exchange-side of this here:
http://connectingshropshire.co.uk/2015/01/fibre-fact...

There are some details of the insides of aggregation nodes, splitter nodes etc in here:
http://forums.thinkbroadband.com/fibre/4375161-fibre...
These guides show how fibre cable needs to be handled to form all the connection work within the nodes, but without detailing the fusion splicing itself.
Standard User Zarjaz
(eat-sleep-adslguide) Sat 27-Feb-16 12:16:21
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Re: Splicing fibres and speed questions...


[re: PaulKirby] [link to this post]
 
Also that last part with the shrinking part, that didn't look like it was done due to it was the same size, heat shrinkable tubing I use all the time and they normally always shrink in diameter,

I use a 30ml splice protector which is heat shrunk over the recently made splice to , err, protect it.

Standard User Ignitionnet
(knowledge is power) Sat 27-Feb-16 18:54:03
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Re: Splicing fibres and speed questions...


[re: PaulKirby] [link to this post]
 
We have, besides maybe some BDUK stuff I'm not aware of, zero native FTTP lines in our entire county so you're not doing badly regardless.

There has been some real pain with regards to street works in London. The powers that be are getting pretty anal about it apparently which may well have held things up.

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