Where to start? Well ... Run your own fiber :-)
Personally, I don't think you need GigE -- 100Mbps or even 48Mbps may suit you well ... You make no mention to how many computers you have on each side, but the server can only handle so many connections (limitation of a single NIC)
For a lot of money you have this option:
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for 1- 4 miles...For less money you have this option:
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...Or for some good, carrier grade 48Mbps MAX (Time Warner Telecom uses these)
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I use those RAD AirMux 200 radios for our backhaul - not bad... With the right module you can even run 4x T1 lines over it for voice traffic or whatever...Hope this helps ...