There are a lot of unknowns here so I'll generalize. I also noticed the word "minimum". As a government worker I understand that to mean "Small Budget".
Two segments can be joined by fiber using fiber to RJ-45 Transceivers. These units can runabout 90.00 each, (you will need two), depending on the speed rating. This is bare budget stuff. You can get a lot fancier.
The type of fiber is dependent upon distance. If this is less the 2 Kilometers Multi Mode will do fine. You mentioned books pertaining to fiber. I use a contractor to run my fiber. I can't do everything.
Now the networking. If you are IPX only joining the two networks is a no brainer. If you are running IP you have two choices. Put both networks on the same subnet or install a router to route between the networks.
I am afraid I did not understand the "different scenario" part of your question.