What is modal dispersion?

Modal dispersion refers to the phenomenon where different modes of light travel at different speeds through a multi-mode fiber optic cable, leading to the broadening of a light pulse. In multi-mode fibers, multiple light paths (or modes) exist due to the fiber's larger core diameter, and as these different modes propagate, they do not arrive at the receiving end simultaneously. This results in the spreading of the light pulse over time, which can limit the bandwidth and overall performance of the fiber optic system.

Understanding modal dispersion is crucial for network design, especially when using multi-mode fibers, as it can impact the maximum distance the signals can be transmitted without significant distortion. Single-mode fibers, on the other hand, have a much smaller core and allow only one mode of light to travel, effectively eliminating modal dispersion but potentially introducing other forms of dispersion such as chromatic dispersion.

The other choices do not accurately describe modal dispersion. Scattering of light pertains to how light interacts with particles within the fiber, loss of signal strength involves attenuation factors unrelated to modal dispersion, and interference from electromagnetic waves refers to a different concept entirely. Thus, the correct interpretation of modal dispersion is directly linked to the broadening of a light pulse in multi-mode fiber.