Hi @laukejas, welcome to the forum 
This comment from another thread is likely relevant:
I’m not aware of any available options for this, but it’s also not an area I’m experienced in, so it’s possible there’s something I don’t know about. In general, many things are possible in theory but may not be readily available and affordable, and may not be robust enough to be a good idea.
From a theoretical standpoint the primary requirements of such a connector would be:
- keeps water out when connected (dry mate-able)
- this is likely feasible, but would probably require some form of locking sleeve, and a seal that gets replaced from time to time
- ideally it would also keep water out when disconnected / if the tether gets cut (wet mate-able)
- if there’s a marine epoxy that bonds well enough to the fiber this could work, in which case a replaceable seal may not be required
- provides a sufficiently good optical connection
- as Etienne described above, the low requirements of a general ROV use-case compared to the optimal capacity of the fiber itself mean that this could be ok (using the “fast” termination method, since the other methods form more permanent connections)
- the connector would likely need some form of locating and/or clamping feature(s), for repeatable alignment and contact between the fibers
- this could be quite challenging to do robustly, in a way that ensures good contact between the fibers while also avoiding damaging them
- some form of protection and/or regular checks and maintenance to ensure the fibers do not get damaged while they are disconnected, and to prevent/remove any particulate matter (e.g. dust, salt, etc) that could block the light path
- maintenance for this could be challenging to avoid damaging the fibers