In fiber optics, a dark fiber is any optical fibre that is currently not being used in the ever expanding fiber optics network. Because the fibers have already been laid out, they can be used by anyone should they be leased from the network service provider such as AT&T or Sprint. However, because they are not currently being used, they have gained the name dark fiber or unlit fiber.

Why Is There Dark Fiber?

The reason for dark fiber is a two fold answer. The first and foremost is the fact that, during the dot-com bubble, many telco (telephone companies) believed that the amount of Internet use was going to continue to grow exponentially. It was believed that data traffic would grow so much that telephone companies wanted to have their particular regions so cornered off and secure to ensure that they continued to show record profits.

The issue with this is that, as they added more fiber, it suddenly became possible for more to be done on a single fiber. As time went on, the amount of data that could be put onto a fiber was increased by a factor of 100. This resulted in the profits many of these telephone companies had previously made to drop suddenly because it was so much cheaper to transmit data. The general result of this was the bubble exploding; many companies bankrupted and disappeared.

The other reason for the increased amount of dark fiber was the fact that it was cheaper to lay more than it was to lay less. Because the planning, permission gaining, duct and channel digging, and the installation and correction accounted for over sixty percent of the total cost of getting fiber optic lines laid, it made sense to get permission in bulk and to dig in bulk. Therefore, companies planned for the future and developed many more lines than were necessary. While the companies, in the long run, failed, this provided a tremendous network of fibers that, to this day, are beginning to come online and become used more.

Dark Fibre Market Today

With the arrival of capital again after the dot-com bubble, the dark fiber market tightened as companies began to work together. Using a process known as coopetion, providers could trade their lines with others. For example, if provider A did not have access to the region that provider B was a part of, provider B could lease some of their lines to A. The same thing was done, though, on the flip side. This made it possible for these firms to start opening up their dark fibre regions and begin making it available to other companies.