Dark fiber refers to unused or unlit optical fibers that have been laid but are currently not being used for data transmission. Optical fibers are strands of glass or plastic that are used to transmit data through pulses of light. When an optical fiber is "lit" or "active," it is being used to transmit data. However, in many cases, telecommunications companies lay more fibers than they immediately need in order to have the capacity for future growth. These unused fibers are referred to as "dark" because they are not carrying any light or data. Dark fiber can be leased or sold to other companies who want to use the fiber for their own data transmission needs. Leasing dark fiber can provide significant benefits in terms of bandwidth, latency, and control over the network. Dark fiber can be used by businesses, schools, hospitals, and other organizations to build their own private networks, bypassing the need to rely on existing telecommunications infrastructure.