Single Mode Fiber (SMF) is a type of optical fiber used for high-speed and long-distance data transmission. It has a small core diameter, typically 8 to 10 micrometers, which allows only one mode of light to propagate through the fiber. This single mode of light travels in a straight path, reducing the effects of modal dispersion that can impair signal quality in multimode fiber. SMF is designed to transmit data over long distances, typically greater than 10 kilometers, and is used in high-speed, high-capacity optical communication systems, such as those used in metropolitan area networks (MANs) and long-haul telecommunications links. However, it is also more expensive and technically challenging to install compared to multimode fiber. Single Mode Fiber Service is also known as Fiber Optic Service, Lit Fiber Service, or Wavelength Services.