What causes modal dispersion in multimode fiber?

Modal dispersion in multimode fiber occurs due to the phenomenon where light travels through the fiber in different modes, or paths, which can lead to varied arrival times of those light signals at the receiving end. The correct answer focuses on the impact of different optical patch wavelengths on the behavior of light within the fiber.

When using multimode fiber, light sources such as LEDs or laser diodes emit light at various wavelengths. These different wavelengths can propagate through the fiber at different speeds. As a result, when a signal composed of multiple wavelengths travels through the fiber, some wavelengths may arrive at the destination sooner than others. This arrival time difference is what leads to modal dispersion, causing signal broadening and potential distortion of the transmitted data.

In contrast, other options do not directly relate to the specific mechanism of modal dispersion. Different core sizes may affect the overall capacity and types of modes supported, but they are not the direct cause of modal dispersion itself. Different light sources can influence modal dispersion indirectly by emitting light at different wavelengths, but it is the interaction of those wavelengths with the fiber that directly contributes to the phenomenon. Lastly, different coaxial cables are unrelated to fiber optics and do not influence modal dispersion in multimode fiber at all.