Dark fibre
A dark fibre or unlit fibre is an unused optical fibre, available for use in fibre-optic communication. Dark fibre may be leased from a network service provider. Dark fibre originally referred to the potential network capacity of telecommunication infrastructure. Because the marginal cost of installing additional fibre optic cables is very low once a trench has been dug or conduit laid, a great excess of fibre was installed in the US during the telecom boom of the late 1990s and early 2000s. This excess capacity was later referred to as dark fibre following the dot-com crash of the early 2000s that briefly reduced demand for high-speed data transmission. These unused fibre optic cables later created a new market for unique private services that could not be accommodated on lit fibre cables (i.e., cables used in traditional long-distance communication). Motivations Much of the cost of installing cables is in the civil engineering work required. This includes planning and routing, obtaining permissions, creating ducts and channels for the cables, and finally installation and connection. This work usually accounts for most of the cost of developing fibre networks. For example, in Amsterdam's citywide installation of a fibre network, roughly 80% of the costs involved were labour, with only 10% being fibre. It therefore makes sense to plan for, and install, significantly more fibre than is needed for current demand, to provide for future expansion and provide for network redundancy in case any of the cables fail. Many fibre-optic cable owners such as railroads and power utilities have always included additional fibres with the intention to lease these to other carriers. During the dot-com bubble, a large number of telephone companies built optical-fibre networks, each with the business plan of cornering the market in telecommunications by providing a network with sufficient capacity to take all existing and forecast traffic for the entire region served. This was based on the assumption that telecoms traffic, particularly data traffic, would continue to grow exponentially for the foreseeable future. The advent of wavelength-division multiplexing reduced the demand for fibre by increasing the capacity of a single fibre by a factor of as much as 100. According to Gerry Butters, the former head of Lucent's Optical Networking Group at Bell Labs, the amount of data that could be carried by an optical fibre was doubling every nine months at the time. This progress in the ability to carry data over fibre reduced the need for more fibres. As a result, the wholesale price for data communications collapsed and a number of these companies filed for bankruptcy protection. Global Crossing and Worldcom are two high-profile examples in the United States. Similar to the Railway Mania, the misfortune of one market sector became the good fortune of another, and this overcapacity created a new telecommunications sector. Market For many years incumbent local exchange carriers would not sell dark fibre to end users, because they believed selling access to this core asset would cannibalize their other, more lucrative services. Incumbent carriers in