In fiber optic, light can travel in two forms, characterizing two types of fiber: single-mode fibre and multimode fibre.
In multimode fibre the core diameter is large (50 µm – 300 µm), therefore it can transmit more light rays. Some of the signal goes straight down the fiber while the rest of the signal bounces off the cladding. This makes for signal dispersion, which limits the bandwidth. Because the signals are not shooting straight down the cable like they are in single mode, the signals take longer to reach the end of the fiber. Multimode fibre has high attenuation so that is used for small distances and bandwidth.
