I was recently thinking about how I would go about connecting two separate buildings using optical fiber cables. This is mostly for understanding how this would be done to further my mental horizon, not because I actually need to do this. I have never before worked with fiber or PPP, so my knowledge in this area is quite limited.
My first plan was to put a router in each building and connect them with a fiber cable. They would then exchange IP (and other) packets via ethernet. I guess this would work fine and I can find plenty of clues on how to do this on the internet. Specifically I can find offers to buy SFP fiber cables and matching ethernet cards and I guess if I would plug those cables in those cards they would be able to communicate pretty much like any other ethernet connection (right?).
But then I thought: Wait, I have only two routers communicating with each other over this connection, so isn't at least the addressing part of ethernet unnecessary for this? Maybe there's a layer2 protocol that is better suited for this! I searched the internet about this and found, that PPP apparently is such a protocol for communication between exactly two nodes.
However, when I tried to find out how exactly I could communicate via PPP via fiber (i.e. without ethernet), I found some mentions that PPP over fiber is possible and then lots of tutorials on how to use various tools to connect to my ISP via PPPoE and some other use cases that don't involve fiber at all. I found no information about what kind of hardware I would need to do this or if I would need any special software to set up the connection.
This scarcity of information about this lead me to question even more if this is actually a good idea. Is PPP actually something I should consider using for this use case or am I overthinking this and should just use ethernet or something else entirely?