Dark fiber is the popular denomination that is attributed to fiber optic circuits , which have been deployed by some telecommunications operator , but they are not being used. The connectivity of the fiber is marketed raw, so it is the customer who applies transmission technology that best suits their needs, thereby improving the yield obtained since unnecessary conversions are avoided protocols.
When a telecommunications operator deploys its dark fiber network, it has to make a large investment to build the pipelines and lay the fiber optic cables. If in the future it were necessary to expand the capacity of an existing network, it would be necessary to lay and connect additional cables. Given the cost of this operation, it is more attractive to oversize the initial network by installing more fiber optic cables than are necessary.