What does the term ‘modal dispersion’ refer to in fiber optics?

Modal dispersion refers specifically to the phenomenon that occurs in multimode fibers where light pulses broaden as they travel down the fiber. This broadening happens because different modes of light follow different paths through the fiber, with some modes taking longer than others to reach the end of the fiber. As a result, when a light pulse is transmitted, it may spread out over time due to these varying travel times, which leads to a distortion of the signal and can limit the bandwidth and distance over which the signal can be effectively transmitted.

This type of dispersion is particularly significant in multimode fibers, where many modes are supported, unlike single-mode fibers, which only allow one mode and thus minimize modal dispersion. Understanding modal dispersion is crucial when designing fiber optic systems, as it directly impacts signal integrity and transmission speeds.