If TPON cabinets were passive, how did they convert the light signals into something that would travel down a copper pair?

PON networks while passive do need power to the lasers at each end of the fibre.

In reply to a post by MrSaffron:

If TPON cabinets were passive, how did they convert the light signals into something that would travel down a copper pair?

PON networks while passive do need power to the lasers at each end of the fibre.

And the old-style phones at the end of the copper need that -50V level to work at, and to be able to signal on/off-hook.

That voltage has to come from somewhere.

Andrew

I wasn't involved in the provision of that bit of the technology, but we never had to provide power at the final splitter ( or the intermediate one) in the way they do with FTTC.

I wonder now if as all the estates we fed would have had street lighting and if it was fed directly off that by the builder. ( It never seemed to be affected by power outages either though, but all the power infratructure for the estate would be new as well). Certainly no batteries or other power infrastructure but must have got 50v from somewhere. ( The pillars are amazingly small.)

Certainly the intermediate spitters needed nothing, jusr split the wavelengths into 30 different fibres.

Same as fttc rollout then aggregation nodes and splitters don't need power either

The reason I thought the TPON cabinets had power to them is that I could swear blind that I've seen a sticker on one to that effect. I'm sure I've also seen a training document to say to stay clear of one part of the TPON cabinet as it has power to it. I could be wrong though.

I don't know what you mean by pillar by the way, I'm talking about those big, wide, grey TPON cabinets.

I've just been googling to find descriptions of a TPON network architecture, and everything (not BT specific) generally seems to put the remote electronics into an ONU that is placed in the home - effectively a variant of FTTP. These descriptions do include a passive splitter - which may be the small pillar, rather than the large cabinet.

However, I've come across a 2005 Analysys report for Ofcom, as part of their study into the "cost of the BT local loop network".

It has this to say about TPON:

In reference to stakeholders.ofcom.org.uk/binaries/consultations/copper/annexes/loo...:

There have been within BT a number of small trial scale deployments (of order 30,000
lines � approximately 0.1% of all BT lines) of TPON systems. Whilst these trials have
undoubtedly shown that such systems are feasible for either a fibre to the DP architecture
(in the past) or a fibre to the premises solution (in a more recent trial), they have not yet
demonstrated economic viability for the current service set. We understand that a new
build of TPON would use a similar duct layout to the existing network (i.e. a �tree�), and
that it would therefore face very similar costs to the existing network for duct and fibres.
Unfortunately for the economic case for TPON however, there is an additional significant
cost, the CPE (Optical Network Unit, ONU), currently costing several hundred pounds per
line: accordingly significant additional service revenues would be needed to make it
attractive compared to the existing architecture. It is therefore not a modern equivalent
asset we will consider further in this study.

That suggests the ONU has been tried in both the premises, and in a DP-like location.

It also has this to say on power backup:

We understand that the BT TPON deployments with fibre to the cabinet have of order 8hrs of battery backup
power.

Use of battery backup suggests mains power is needed in the first place.

Given the numbers of tpon users with adsl when copper overlay was added between cab and exchange the ont in home I think was rare

I've never seen any kind of ONU in a home and I've worked a lot in ex-TPON areas. I'll do some digging and find out exactly how BT did it.

I've found out the info, don't ask for a source because I can't give one but larger business customers could be served by an optical unit inside the building. Small businesses and residential customers were served by an optical unit housed in street cabinets. Each cabinet connects up to 32 lines or 128 lines depending on the cabinet used.

I can confirm that the grey TPON street cabinets 100% DO have 240v power to them. I've found the warning that I was talking about before.

Edited by deleted (Sat 05-Sep-15 14:16:18)

That makes perfect sense as something has to power the optical/electrical interface, and I don't think a 50V supply from the exchange would do it (due to resistive losses), nor do I think that "reverse power" from the premises be at all likely (I've never heard of such a thing).

What I imagine might be possible is that a number of the TPON grey boxes are supplied via low voltage supplies from a nearby one. That's certainly what VM do with their green boxes.

As to whether the supply to the TPON boxes is up to the job of supplying an FTTC cabinet, I've no idea. I suspect TPON used relatively low power.