http://www.zetta.net.au/services/networks/dark-fibre/ Dark fiber optics may sound mildly sinister but in fact they are merely fiber optic cables which are currently not in use, or unlit. While a fiber optic cable in use by someone leasing it may still be referred to as dark fiber that may be because they have no specific long term use and may return to unused status as soon as the lease expires.

1. DARK FIBRE
Dark fibre allows your business the freedom to create your own
dedicated network for any purpose including connecting office
branches and disaster recovery sites.
Dark fibre is not managed (lit) with any ZettaNet equipment
providing you with the opportunity to securely operate the link
using any technology and network protocols you require including
single frequencies, CWDM and DWDM technologies. The dark
fibre service can be delivered as single or dual core
for additional bandwidth and redundancy.
ZettaNet can provide point-to-point, point-to-multipoint, self-healing
ring or mesh dark fibre network topologies in most capital
cities. For more information visit our website :
http://www.zetta.net.au/services/networks/dark-fibre