Most routers have a port called SFP if they support fiber. There are a couple of different types of optics used so you must buy those separately to match the type of fiber you are connecting to. Mostly this is a distance related thing as to which you choose.
If you are talking about a fiber to the home solution say like verizon fios those use very special things. Even if you could buy the optics they likely would not allow you to install them. Most home delivered ISP on fiber require you to use their box commonly called a ONT. This converts the fiber to standard ethernet much like a modem.
Now if you are talking a commercial connection those you can get raw fiber you connect to your router. Those commonly run on single mode fiber using ZX sfp but you need to check with the ISP for sure since they must use the same optics on their end.