Remember that one pair of fibre can get an awful lot down it using CWDM or DWDM. I personally would have 2 fibres coming in and ideally have these taken back to 2 major peering points (if you're not too far away from these) and have the fibres lit at gigabit (if you use CWDM it's relatively cheap to add more waves). I'd then route at the peering points and pick up transits there then use an IGP to handle failover at the DC end.