I have been surveying and patching up some fibres this morning in order to dual-feed our cabinets from the VSS (Cisco 6509) rather than from individual hubs (Cisco 3750-G) around campus. We have two VSS feeds from two server centres so if one route goes down the traffic routes the other way and nobody notices (in theory).
A few trays I have come across only have the multi-mode fibre terminated so I will have to terminate the single-mode to have enough fibres to dual feed all the cabs (40 or 50... to begin with).
This morning, however, I came across a tray that only had four multi-mode and 4 single-mode terminated. We need 8 fibres and would prefer not to have to use mode-conditioning leads. Also it would be nice to be able to patch up from the VSS, keeping the aggregation link from the hub connected until early one morning when we just swap the link therefore having minimal downtime.
So I opened up the tray and to my horror found the other tubes were empty. The fibre coming in is only a 4+4! I guess this tray was put in about 15 years ago when fibre prices were a lot higher per meter and nobody saw the need to have more than 8 cores.
So some 'bodging' will be needed until we can get some more fibre pulled through.
It also looks like we will need about four or five 24 cores putting in for other cabs which we have not started yet. Probably looking at around £70K+.
So, in summary, plan for the future, your network will probably grow many times over the size it is now.