ADSL - The physical layer

[KingDaveRa]

Now, I'm sure somebody will know this. I've found some stuff, which kinda gives an answer, but I'm not sure.

I'm aware of what goes on at the logical layer in terms of how ADSL works. What I've been mulling over lately is what goes on at the PHYSICAL layer.

At some point, the ADSL signal is injected/lifted by the DSLAM, and the POTS bit goes into the exchange gear.

What I've so far found suggests this happens:

Local Loop --> MDF --> DSLAM --> back to MDF --> Exchange switchgear.

So basically, the DSL/Voice signals enters onto the MDF, are routed into the DSLAM, which hoiks out the digital data, then the cable is routed back to the MDF and into the exchange. The DSLAM effectively has an 'in' and 'out' side.

Is this the case?

This picture (http://www.flickr.com/photos/riceyo/2056979411/in/set-72157603271928916/) makes me think this, along with reading other bits and bobs.

[GeeDee]

Not sure it would go back to the MDF - as that's just (afaik) where all the copper lineplant terminates.

I believe it should be:

SMPF:
Local loop -> MDF -> 'Splitter' -> Chosen providers DSLAM via tie pair & chosen providers switching gear (which would be BTw in all current examples) ( --> rest of world)

FMPF:
Local loop -> MDF -> Chosen providers MSAN via tie pair ( --> rest of world)

[bvark]

http://www.openreach.co.uk/orpg/products/llu/signup/downloads/LLU-PB-TRAINING_PACK_VER1.2_(R).pdf is pretty thorough

[KingDaveRa]

So it looks like the voice signal goes in either via a splitter as a separate box, or via the DSLAM doing it.

That LLU document is fascinating tho :o

[Portia]

I like the sound of this :)

CPs have a right to access their co-mingling PoPs 24*7