Dark Fibre
Fibre installations often consist of multiple cores (for example ours is eight core) but often few of these cores are used (we only use two). The others are only used in case of failure - or to handle increases in network demands. This unused fibre (also known as Unlit fibre) is referred to as Dark Fibre - an indication that fibre requires light to operate.
Fibre is typically used for infrastructure installations (although more recently for desktop installations too) and difficulties and high costs may be encountered physically laying the optical fibre as it needs to be handled with care (the cores are very delicate). This fibre may also be installed underground or in other difficult to access places. Because of this it is common to put extra fibre in at the time of installation to reduce costs in running extra lengths at a later date.
This definition has been bought to you by: Jason Slater Weblog Tech Fact.