What is the definition of modal dispersion?

Modal dispersion refers specifically to the phenomenon that occurs in multi-mode fibers where light can take various paths or modes as it travels through the fiber. Each mode corresponds to a different path that the light can take, and because these paths have varying lengths, it results in a spreading of the light pulse over time. This spreading can cause overlapping of signals and limits the bandwidth of the fiber optic communication.

Different modes travel at different speeds and arrive at different times, leading to broadening of the pulse. This effect is particularly significant in multi-mode fibers, where several modes are supported, and is a key limitation for distance and speed in fiber optic systems. Therefore, the definition that describes the spreading of the light pulse due to different paths taken by light modes in multi-mode fibers accurately captures the essence of modal dispersion.