Multimode Fiber (MMF) is a type of optical fiber that is used to transmit data in optical communication systems. It is characterized by a relatively large core diameter, typically 50 to 100 micrometers, which allows multiple light modes to propagate through the fiber. MMF is used in applications where data transmission distances are relatively short, such as in local area networks (LANs) and data centers. The larger core diameter of multimode fiber provides higher bandwidth compared to single-mode fiber (SMF), but also results in modal dispersion, which can limit the maximum transmission distance and impair signal quality. Multimode fiber is commonly used in installations where cost and complexity are important factors. It is also used in applications where the signals being transmitted are not particularly sensitive to modal dispersion, such as in Gigabit Ethernet and Fibre Channel networks. Multimode Fiber Service is also known as Fiber Optic Service, Lit Fiber Service, or Wavelength Services.