Multimode is a type of fiber-optic cabling that allows multiple signals to be transmitted simultaneously. Multimode Fiber (MMF) has a core diameter, typically 50–100 micrometers, has ability to transfer multiple modes of light through the fiber core, uses lower-cost electronics (LED, VCSEL) operates at. Multimode fiber (MMF) is an optical fiber designed to carry multiple light propagation paths—or modes—simultaneously. This is made possible by its relatively large core diameter, typically 50 or 62. 5 microns, compared to the ~9-micron core in single-mode fiber. While they may seem obscure to some, they play a central role in the architecture of modern digital ecosystems.