Yeah I have 4 fibre strands coming into the external CSP. Only 1 (blue in colour) is hooked up the 4 port ONT, 3 are kept as spares all nicely coiled up. This means I could (in theory) have 3 additional ONTs without the need for any new blown fibre.
Thanks for the pictures.
In many cases people don't have spare fibres to their premise anyway, I don't, it is a single fibre from the DP run under ground with no outside connector box, in my case you can't see any indication from outside I have fibre. My install is the same as yours with the same conduit you have for the old telephone line, but my fibre comes into the house using the same hole behind the original conduit as the telephone wire, so it looks no different with no wires or fibre visible at all on the outside, a very neat job.
If my fibre breaks, they would need to pull out the broken one and pull in another fibre, although that task first time round took only minutes. We have here an 8 port connector at the DP amongst 5 properties, but I don't know if only 5 are lit or all of them are lit for use.
Technically of course it is possible to have more than one fibre, so question isn't whether it can be done, it is whether Openreach will do it and install two ONTs in the same house. End of the day it is purely an Openreach business decision rather than if technically possible, and if there is no fibre capacity they can add some of course at their or the customers costs.
Regards
Phil