Does apply to cabinets but to less extent hence why three power masks are used based on distance from exchange.

In reply to a post by billford:

Thus the (relatively) powerful outgoing VDSL signals would interfere with the (much weaker) incoming ADSL signals, some of which may be coming from very long lines, and degrade the performance of those lines to an unacceptable degree.

That is a very good explanation of the potential problems that can beset a Cabinet, where it has a mix of locally generated VDSL signals, & "carried-through" ADSL signals!

So what is the difference at the Exchange end, though?

Have spoke anfp with various people and difference in uk is that a cautious approach is taken, a lets try and then fix it approach is more prevalent in some places. Hence some places rolling out before international ratification

In countries were adsl2+ takeup is less its less of an issue ie less rf in cable bundles. Also if just adsl probably easier. Some countries replace adsl with vdsl.

The presence of llu is a big uk difference ie talktalk sky and others have input into anfp

Originally believe aim was that short eo would be fttp but cost realities kicked in

Messy typing as on phone

In reply to a post by MrSaffron:

Originally believe aim was that short eo would be fttp but cost realities kicked in

I suspect that that provides a "hint" on the situation in as much that there was an assumption that short EO wouldn't be an issue as the "aim .... would be fttp"!

Certainly, the document, that jchamier linked to, states that "It is for future study" (which implies that EO VDSL hasn't been considered yet!)

well here's just a sample of the complexity relating to near and far-end cross-talk

http://www.princeton.edu/fastcopper/eusipco.pdf

I nave also perused ND1602; and generally agree with your comments - but there is a qualification in Part D, regarding EO lines-

"
D.1 Introduction
This part of the ANFP specifies the PSD Mask that applies to transmission equipment connected to the MDF at an MDF site when that MDF is connected to cables routed directly to the NTP (i.e. without being routed via a SLCP) and where those cables are not in a cable sheath with any metallic access cables routed via a SLCP.
"
Presuming that the implication is that these are the same (EO) cables-
"when that MDF is connected to cables ...... and where those cables...."

That does seem to imply a possible VDSL interference problem with any "Part A" sheathed cables, going to SLCP (PCP) Cabinets, where I understand there are HF Reject filters fitted to confine the FTTC-VDSL signals to the (very) final stretch from the SLCP/PCP in to the Customer's Premises.

That is, preventing the FTTC-VDSL signals leaking back to the Exchange MDF etc electrically, although probably this would be at extremely low levels given the likely Attenuation etc.

=======================

Another aspect that I wonder if it has any bearing on the matter.

Generally the SLCP/PCP cables will pass through the Exchange walls in relatively tidy groups; and at the SLCP/PCP, gives a nice, concentrated node "near" the various Customer Premises, that injecting the VDSL signals at such locations is relatively easy to do.

I suspect and would appreciate confirmation from someone with good Exchange Practice knowledge, that EO lines tend to pass in/out of the Exchanges at relatively widely scattered points, heading to/from the Jumpers and Risers etc (Or have the Jumpers and Risers gone?)

If the latter is the case, I suspect that to re-arrange them in to a tidy group so that a pseudo "FTTC SLCP/PCP" in the Exchange to provide VDSL to them, would involve quite a lot of extra work, tending to be almost unique in detail in each Exchange; and with a varying quantity of those pseudo cabinets, dependent on the quantities of EO lines and whether the specific EO lines are suitable.

Density of the cable bundles as they travel around the building, which increases the scope for crosstalk.

In reply to a post by eckiedoo:

Generally the SLCP/PCP cables will pass through the Exchange walls in relatively tidy groups; and at the SLCP/PCP, gives a nice, concentrated node "near" the various Customer Premises.

These bundles of E-side lines are indeed in tidy groups, of perhaps 1,000. You'll also find that they have a tendency to be pressurised (with air) as a way to keep moisture out, and as a way to indicate breakage.

There is some sort of manifold at the PCP-end of the line that provides the far-end seal.

E-side lines stay pretty much untouched. breaking into them for trivial matters is a no-no.

There's some posts here, including a photo of pressure gauges and a link to an Ofcom document that gives titbits about the access network (first post of second page).

Thanks for the fast reply, link etc.

You have confirmed that the SLCP/PCP cables pass through the Exchange walls in sealed, pressurised sheaths containing large numbers of pairs, what is the situation with the EO lines?

Do the EO lines range from single pairs "to the premises next door", to anything approaching being mini-versions of the SLCP/PCP cables above?

My feeling, from things I have read online, is that EO lines tend to leave the exchange in cable that is nearer to E-side in style, rather than D-side. That is, that it is still grouped quite strongly as it leaves the building. Perhaps more cables, each smaller than full E-side cables, but not individually.

[Note 1: The E-side cable I talk about can be made of separate cable lengths that are jointed. However, this is a one-time jointing operation, and the sheathing surrounding the set of joints is restored permanently to prevent water ingress. Perhaps, for old cables, in soldered lead sheaths.]

[Note 2: As I understand it, pressurised E-side cables tend to terminate in the ground (ie jointbox pits in the pathway), where they are jointed to short cables up into the PCP. There they are jointed, as needed, to a short linking pair that takes the connection back to a separate cable down underground to the D-side cables. The short linking pairs are the joints that are made/unmade when doing fault repairs, or routing through FTTC cabinets]

The main structural difference in the EO case is that the main EO-cable terminates underground, where it is jointed to more local D-side cables directly.

But I must add caution here - that is my interpretation of the way I understand it from the way I have seen things written written. It certainly doesn't come from absolute confirmation.

You might like another thread on the E-side and (in one of my favourite set of pictures) an american story under a flooded Verizon exchange