Reading through the forum I didn't see this suggestion posted so I figured I'd throw it out.
Fiber GBIC's; You can get them off e-bay at $10-50/unit and the controllers for even less. Max range on the old ones are in the km's but the newer one's do 40km+. Frame relay did 100km's per strech of line if memory serves; the db output of some of the newer repeaters is as high as 40db whereas cd optical drives are in the 15db range. The chip datasheets are also available which means harvesting controllers and building them into custom circuts is possible. You can also use fiber line to focus multiple beams where you need them.
