Single Mode Fiber (SMF), one of two types of optical fibers, is a single glass fiber strand that transmits a single mode or ray of light over long distances.

By contrast, the multi-mode fiber (MMF) offers high bandwidth over moderate distances. SMF’s core, that through which the light travels, is much smaller than that of MMF through which a single light wave passes, and thus provides a stronger signal and a greater transmission rate — nearly 50 times that of MMF. It is also referred to as a single-mode optical fiber, uni-mode fiber, mono-mode optical fiber or single-mode optical waveguide.