Copper / Fibre bandwidth after FTTC arrives?

[iainH]

Our village's new cabinet is installed and we keenly await (yawn) the arrival of the fibre cable and some mains power to the cabinet, and many of us can't switch over fast enough to our providers' fibre products - I expect I will go with BT Infinity 2 as I have no complaints with my Business Account except poor speed and reliability of the existing copper connection.

However, I am being asked by others: "Will we see our speed improve if we choose not to take up our provider's fibre product?" i.e. unless they take some new product, will their bandwidth remain terrible?

How does it work? Will the existing copper cables still carry broadband traffic in addition to the new fibre cable (I assume so) and, if so, will "copper" broadband get any relief from less broadband "contention"?

I expect most users of this forum will have either moved over the fibre as soon as it was available and will not have noticed any improvement side-effects in bandwidth over the copper, but any real insight into this would be much appreciated.

Thanks.

[Burkem5]

Hi IainH

I have had to speak with a colleague about this as to be honest i was not quite sure myself.

Essentially this can in theory improve the connection speed - not to fibre quality but still a good bit.

This would only improve the connection if the cabling between the cab and the exchange was of poor quality.  You would see an increase similar to what would happen if we ran brand new copper cable to the cabinet.

I hope this answers your question

Thanks

[MHC]

Those who chose not to move from ADSL based products to VDSL based products will not see any significant difference in their connection speeds - a further comment later.

ADSL and voice are combined onto the customer's copper pair at the exchange and delivered all of the way from exchange to cabinet in a large bundle of pair (100 or 200 pairs) and from cabinet to premisies on a smaller bundle via underground ducts and poles.

VDSL (FTTC) is slightly different.   The voice circuit comes on the same copper pair as before from the exchange to the cabinet.   At that point the FTTC cabinet which is fed by fibre optic cable provides the combining of voice and data onto the copper pair.   That is then delivered to the customer premises.

One reson for slow speeds is cross talk - the signal from one pair is picked at very low level in an adjacent pair where it appears as noise.   With large numbers of pairs, a small amount from each one being picked up can result in a higher noise floor and thus a slower speed.     By reducing the number of ADSL connections back to the exchange, the overall noise will drop just a small amount which could result in a small increase in speed, however, this could be offset by noise introduced by VDSL connections.   So,  possibly a small incease, but nothing to "write home about".

As for contention - contention ratios were removed years back.   As for congestion,  there is very little in te network and again no improvement.

[iainH]

You both seem to confirm what I had deduced. Thanks for your replies.

And if anyone can quote actual numbers from their experiences of even "slightly better" or "not noticeable at all" ADSL bandwidths after fibre was brought to their cabinet then I would be be glad to see them. 

[iainH]

@Burkem5 thinking about your answer a bit more ("This would only improve the connection if the cabling between the cab and the exchange was of poor quality.") Yes, the copper cabling (plus we have some aluminium for some voice lines) is very poor from our cabinet to the exchange.

So ... so I can begin to fill a gap in my understanding I'd be really grateful for simple answers to these questions:

1. "Will ADSL customers not upgrading to Infinity be receiving broadband on the leg between exchange and their cabinet via the old copper cable OR the new fibre cable?"
   
   
2. Then ... After FTTC is connected are the old copper cables between exchange and old cabinet just used for voice?
   
   
3. Then ... If all broadband comes to the cabinet via fibre after FTTC, then is this the chain of transmission:
   I. for users not going to Infinity?:
   (Exchange <->VDSL<->New Cabinet<->Old Cabinet<->ADSL(over copper)<->Premises )
   II. And for those going to Infinity:
   (Exchange <->VDSL<->New Cabinet<->Old Cabinet<->VDSL(over copper)<->Premises )
   III. And for those going to FTTP or Fibre On Demand:
   (Exchange <->VDSL<->New Cabinet<->VDSL(over fibre)<->Premises )
   
   
4. Then does case I above explain an improved ADSL connection that  "... can in theory improve the connection speed - not to fibre quality but still a good bit"?

..... or am I completely at the wrong end of the stick? Quite possible!

[MHC]

ADSL customers will continue to use the original copper pair from exchange to cabinet and cabinet to premises. 

Only VDSL customers will get their data from the fibre connection to the cabinet.

When FTTC is enabled,   voice will continue to be supplied to all customers on the copper pairs from the exchange.

Your transmission chanins are Completely wrong in all cases and FTTP/FTTPoD are totally different products from ADSL and VDSL and best left out at the present time.

[iainH]

Hmmm "You would see an increase similar to what would happen if we ran brand new copper cable to the cabinet." vs "Nothing to write home about".

So my original question is not clearly answered yet then. How to square these two views?

Be great to get some actual figures from some actual tests!

@MHC can you show the correct transmission chains? That would be very helpful.

And please include the FTTP and Fibre on Demand chains if you know them. 

Many thanks.

[MHC]

Cu - Copper Pair

PCP - Primary Connection Point (Cabinet)

ADSL Customer - this is always the same (in the UK) irrespective of whether the cabinet is VDSL enabled or not.

Voice>>>>Exchange-DSLAM>>>>Combined Voice & ADSL Link on Cu>>>>PCP>>>>Premises

Data (ADSL) >>>^^

Infinity Customer:

Data >> Exchange >> Data on Fibre >>>>VDSL Cab-DSLAM>>>Combined V&D on Cu>>OldPCP-Dside>>Premises

Voice >> Exchange>>Voice on Cu >>OldPCP- Eside>>^^

FTTP/FTTPoD

Voice>>>>Exchange>>>>Combined Voice & Data on Fibre >>>>Fibre Aggregation Node>>>>Premises

Data >>>^

[iainH]

Very succinct.

Thanks for taking the time to transmit your knowledge!  

I'll be intersted to see the effect  on peoples' ADSL bandwidth after the fibre arrives; to what extent a reduction in noise can be detected.

[MHC]

Remember, every line will be different and it will be different throughout the day alongside variations caused by temperature and rain.

To get a meaningful figure it would be necessary to compare a month of data from 2012 against the same for 2013.

However,  prior to moving to FTTC I was on ADSL2+ giving around 6Mbps.    When I changed over, a neighbour who shares the cable including dropwire confirmed that he had seen no change in his speeds.   Other cases I have seen have "claimed" a few kbits or 10s of kbits but nothing major.