The installation of fibre to our block was overseen by open reach and involved access points being fitted at the entry to each of the flats.
A multi fibre cable is run from the floor DP node, or direct from the splitter. As this cable passes through each of the little junction/splice boxes outside each flat, the cables sheathing is removed to provide access to the multiple fibres inside which are individually coloured for identification purposes. The routing information on the install will identify the colour to be used, and the invisilight is then either spliced on, or in some cases has a nasty s/c to s/c coupling affair. The fibre is then glued into position on top of skirtings and door frames to reach its final location by the ONT. Discreet formers are used for bend radius protection, and premade micro tubes can be used where the fibre passes through walls to stop the risk of sagging in voids.
So, for instance, flat one gets fibre 1/blue, flat two/fibre 2/orange etc, etc so all fibres pass through the junction boxes, but they may not all get back to the next node.
If not already lit, then a light source will be applied at the ONT end, and this iced though to the splitter.
At least that’s how it *ought* to work.
Experience of some flats round this way, where Openreach had provided the fibre to the splitters, but the rest had been done by contractors working for the developers was far less satisfactory.
The common issue was that the invisilight fibre into the flats had been fitted by ham fisted morons … with multiple breaks in the fibres, or such high light loss readings, you couldn’t get a steady PON light.
The usual fix was to re run in eezee bend, often from ONT all the way back to the splitter. Not pretty, but at least it worked.
I feel sure/hope that things have improved .