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Standard User Pheasant
(member) Mon 19-Oct-20 21:38:55
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Re: How are exchanges connected?


[re: Nick_W789] [link to this post]
 
In reply to a post by Nick_W789:
In reply to a post by chriswillsher:
Thanks for that helpful information. Will it be possible to know where the head-end exchanges are located in the same way that you can now map the copper exchange network?

One trick is if there is any FTTP only near you (eg new build), to put one of those addresses in the BT Wholesale checker. It will say 'Connected to XXXXX exchange' - that is the fibre headend.

Actually no it is not the head end exchange (necessarily).
Standard User dect
(fountain of knowledge) Mon 19-Oct-20 22:34:00
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Re: How are exchanges connected?


[re: Pheasant] [link to this post]
 
In reply to a post by Pheasant:
Actually no it is not the head end exchange (necessarily).
Your response took me by surprise.

I was also lead to believe that for a fttp only property (without any copper) the DSL checker shows the head end exchange instead of the local exchange, if the exchange shown on the DSL checker is not the head end exchange nor the local exchange what purpose does it serve and why is it in the results on the DSL checker.
Standard User Pheasant
(member) Mon 19-Oct-20 23:13:27
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Re: How are exchanges connected?


[re: dect] [link to this post]
 
In reply to a post by dect:
In reply to a post by Pheasant:
Actually no it is not the head end exchange (necessarily).
Your response took me by surprise.

I was also lead to believe that for a fttp only property (without any copper) the DSL checker shows the head end exchange instead of the local exchange, if the exchange shown on the DSL checker is not the head end exchange nor the local exchange what purpose does it serve and why is it in the results on the DSL checker.

Apologies I missed the ‘“only” in the statement, otherwise if FTTP is enabled (and copper is present however not necessarily active) then just the local exchange is shown on the checker. A better system imho would be to indicate both where the property is served by fibre and copper, but no doubt too complex


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Standard User witchunt
(experienced) Tue 20-Oct-20 07:56:11
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Re: How are exchanges connected?


[re: chriswillsher] [link to this post]
 
The headend is in Perth.
Standard User chriswillsher
(newbie) Tue 20-Oct-20 08:09:30
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Re: How are exchanges connected?


[re: witchunt] [link to this post]
 
Thanks I suspected as much. Our local exchange is really only a small hut and is obviously not part of the fibre network at all. We are about 12 miles from the centre of Perth. These head end exchanges must cover quite an area. One can only speculate the cost savings that will eventually be realised by removing the copper network throughout the country. Hardly a day goes by without seeing an Openreach engineer mending a faulty copper connection.
Standard User chriswillsher
(learned) Tue 20-Oct-20 08:57:50
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Re: How are exchanges connected?


[re: chriswillsher] [link to this post]
 
I have found an excellent description of the physical construction aspect of laying fibre networks throughout the country. This is a few years old and some of the connection technology might have changed but the basics are still very relevant.

Building fibre networks
Standard User kitcat
(experienced) Tue 20-Oct-20 14:55:18
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Re: How are exchanges connected?


[re: witchunt] [link to this post]
 
witchunt

COST

It worked in S Wales ( think it still does) but it cost too much and as usual with certain suppliers the promises exceeded the delivery.

The actual cost of transferring from one technology ( RCU/RSS) to another (MSAN) by rejumpering was too much to ever cost in with VOIP on the horizon. (and OFCOM wouldn't let the cost be recovered).

So decision was to sweat the assets until they wore out sometime around 2025 and move to VOIP. With call revenue trending towards zero the was no profit in voice to pay for anything else.
Standard User kitcat
(experienced) Tue 20-Oct-20 15:15:53
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Re: How are exchanges connected?


[re: Pheasant] [link to this post]
 
Pheasant

I think you are getting confused there were around 51 exchanges still on (20CN) ADSL last year. The rest were all on 21CN broadband ( ADSL2+ / VDSL / FTTP)

These were all very small ultra rural places.

PSTN Voice apart from a small subset (in S Wales) are all still on 20CN. Salisbury is likely to be the first Voice area to be migrated completely to VOIP ( via FTTP) and Mildenhall ( Via FTTC) then the is a published programme to close new provision on 118 further exchanges announced in May. This will then be a continual programme. OFCOM are just starting a consultation of the ability of OR to start forcing migration 2 years after the closure of new provision.
Standard User Pheasant
(member) Tue 20-Oct-20 19:10:10
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Re: How are exchanges connected?


[re: j0hn83] [link to this post]
 
In reply to a post by j0hn83:
In reply to a post by mwarby:
How far can FTTP go in terms of bypassing the smaller exchanges 10 miles, 50 miles etc ?


Around 20km using the standard deployment method.

They can increase this distance by using Subtended Head Ends, making it more like 20km from where they install the S.H.E (ideally next to an existing Huawei FTTC cabinet).

Wonder if Openreach ever did or do specify any distance limits with their FTTP infrastructure?

I ask because I stumbled on an old (ancient really, 2013!) Openreach PIA reference offer document online that had a GEA FTTP schematic diagram, where a 28dB optical loss budget was noted, from OLT to the ONT.

This max figure would have included various necessary PON splitter losses, presumably up to 32 way splitting per core (but 128 way is noted, I guess in line with the GPON standards) as well as splices and connectors along in the full link.

Not sure what splitter losses they allow for, but a quick search says something in the order of 17 dB for combo of two series PON splits, so some fag pack maths and you're down to around 11 dB budget for the fibre attenuation @ around 0.36 dB per km, which is around 30 km or so, with no margins....

All back of fag packet of course! wink
Standard User Pheasant
(member) Tue 20-Oct-20 19:19:32
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Re: How are exchanges connected?


[re: kitcat] [link to this post]
 
In reply to a post by kitcat:
Pheasant

I think you are getting confused there were around 51 exchanges still on (20CN) ADSL last year. The rest were all on 21CN broadband ( ADSL2+ / VDSL / FTTP)

Yep that's what I thought I had said, around 51 exchanges left to convert to 21CN...no?

Interesting about the PSTN wind down.
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