In reply to a post by paulb100:

I just though FTTP was an extension on from FTTC cabs.. I suppose it has something to do with the Mutliplexing at the cab DSLAM etc?

Think of BT radiating bundles of fibre out from an exchange (or, as Mr Saffron says, handover node). The bundles have *many* fibres within them, and they go to form a spine or backbone of fibre. This spine is common to all 3 products - FTTC, Native FTTP and the FTTP on demand - even if all 3 aren't available in any one area.

Along the spine are located a number of "Aggregation Nodes" - a fancy name for a box with a set of splice trays within, allowing joints in some of the fibres. Again, these are common to the 3 technologies.

For an FTTC cabinet, a fibre (probably more than one) will be taken from the spine at an aggregation node and jointed (spliced) to one heading towards the cabinet. The splice will be in the aggregation node. This fibre will be used exclusively for traffic for that cabinet - a concept known as point-to-point.

For an FTTP product, a fibre is taken from the spine (spliced again at an aggregation node) and used to service up to 32 separate properties as a shared service known as a PON. The single "master" fibre is spliced to those 32 other fibres in a different node known as a splitter - it looks the same as an aggregation node, and is also made of many splice trays.

This FTTP setup, in the ground and on the street, is identical for both FTTP and FTTP-on-Demand. The only difference is the way in which it is administrated, ordered and paid for.

So the FTTC cabinet isn't physically used in any of the FTTP products. In 20-30 years time, it can be taken away leaving a pure FTTP network hidden in the ground.

suppose it would mean another 'pure fibre' DSLAM in each cab too??...so it makes sense just to run it direct to the exchange.

A DSLAM is only needed to interface with copper. Pure fibre just needs to be spliced in a splice tray.

Some videos to watch, to see the different bits of equipment:
FTTP
FTTC
FTTx kit being worked on

wow! - amazing info WWWombat - thanks.

I understand, so really FTTP feeds into the fibre 'beyond' the FTTC cab at an aggregation node...

is each propertys connection a single strand of fibre to the exchange? (as splitters are mentioned) if not how is your traffic identified? diferent colours? also how does it affect performance on shared connections?

thanks

Edited by paulb100 (Wed 17-Apr-13 23:45:25)

In reply to a post by MrSaffron:

Partial fibre = FTTC
Full Fibre = FTTP

Native FTTP = my label for areas with just FTTP
FoD = Fibre on Demand

Any better ideas?

I've picked up your use of "native", but only because it needs some sort of label and I don't want to add to the confusion.

It certainly makes sense to use the simple FTTP name to mean *either* product.

Problem with the word "native" is that it suggests there is some sort of "non-native" variant, or perhaps a hybrid FTTC. Whereas, once FoD is in the ground, the only real difference is in the way it was paid for - so both are technically native.

But otherwise, I can't for the life of me think of a decent way of trying to describe an old "FTTP area" that is now the cheap way of getting FTTP, nor describing the old "FTTC area" in a simple way that shows you can now get both FTTC and FTTP there, except you have to pay more.

It's a marketing nightmare, and we're going to get a lot of people asking why it is cheaper for "him over there" to get the same FTTP kit installed.

Not a single fibre to exchange, that is termed point to point.

A shared system is used called GPON which uses different light frequencies that can be split to cover lots of different premises. Thus saving the need to run hundreds of individual fibres, apart from over the last few metres into each home.

GPON has a 2.5 Gbps speed limit, but a 10 Gig variant has been played with.

@paulb100 - If you want to see more than you ever thought possible about the UK access network, take a look at this presentation from Openreach to the British Computer Society. It dates back 2 years now, but it has some good stats, and a couple of pictures of the way in which both FTTC and FTTP are to be deployed in the field.

@MrSaffron - I didn't think BT were using WDM-PON yet, just keeping it open for the future (see same link).

Right now, the OLT is more likely to be transmitting packets to all the ONT's, which must filter based on address (MAC address?). Upstream likely to be split using TDM, hence the lower bandwidth (both total and to individual lines)

In reply to a post by MrSaffron:

Not a single fibre to exchange, that is termed point to point.

A shared system is used called GPON which uses different light frequencies that can be split to cover lots of different premises. Thus saving the need to run hundreds of individual fibres, apart from over the last few metres into each home.

GPON has a 2.5 Gbps speed limit, but a 10 Gig variant has been played with.

amazing isnt it?? so the different light frequencies must be able to travel alongside each other yes? they dont clash at al..

In reply to a post by paulb100:

so the different light frequencies must be able to travel alongside each other yes? they dont clash at al..

Well the visible frequencies manage to travel alongside each other OK wrt daylight, until you put a coloured filter in front of them. Or get a diffracting medium such as a prism or raindrops to separate them.

Edited by RobertoS (Fri 19-Apr-13 13:34:26)