Not sure what you mean most cameras use ethernet or maybe still coax. There really is no need for fiber and it can not provide power to the camera like the other solutions.
Most ont or fiber modems use completely different technology than boards you find for a PC. Most pc boards are some form of ethernet or maybe something like fiber channel used for disk storage. The key difference you will find is things like ethernet use 2 strands of fiber one for transmit and one for receive. Most fiber broadband solutions are using one signal strand of fiber and run multiple different color lasers to make it appear at 2 or more connections. Most these also carry tv and telephone on other color lasers.
In addition most fiber broadband solutions are shared media, meaning you and all your neighbors are connected to the same fiber strand and share bandwidth. One of the most common methods to control this sharing is called GPON.
Now I guess in theory you could get a PCI board that is compatible with one of these systems rather than use a modem but there are many variations between ISP I suspect if they even exist it will be very hard to find.