Dark fiber is offered by a few AB&T fiber carriers for wholesale capacity to the very large Fortune 100 organzation, carrier or large Federal Government agency.  Dark fiber consist of "unlit" fiber strands that exist in carrier conduit for sale in multi-year leases and where the customer provides their own equipment to connect to make the fiber functional for communications.  This is a very specialized area of the telecom business and we recommend you call an AB&T Channel Manger to engage in talks about dark fiber capacity.