Fibre cable joint

About 1.5km from our house a fibre cable on poles runs past our road (on the way to a single FTTC cabinet serving about two dozen premises). On one of the poles is a cylindrical tube about 30-40cm long and about 80-100mm in diameter with two cable entries, and the fibre cable appears to go into and out of this box. There is no mains electricity supply. How likely is it that this device is intended or could be used to split the fibre so another fibre cable could be run from this?

Unlikely. FTTC cabinets are connected using point to point fibre., not PON .

I did suspect that from reading this site. What do you suppose this box is? Just a passive spliced connection or some kind of amplifier? The total fibre cable length is probably over 3km.
My only reason for hoping this might be some kind of junction is that if they ever run fibre to us the first 1.5km will have to be on the same poles as the cable to said box.

Will not be a fibre amplifier and that would need power to work.

Don't know official name but just had assumed they were housings for splice between two runs of fibre, or could be mechanical connector rather than spliced.

Have seen them on country roads heading off to an FTTP area and others on what looks like a long run to a cabinet.

Thanks. That makes sense, there must be limit to how long made-up cables are. Same idea as the boxes for joining copper pairs, then.

These can be used for repairs too. If someone slices through the cable whilst cutting hedges with a tractor for example.