One way to reduce modal dispersion is to?

Reducing modal dispersion is essential for enhancing the performance of multimode fiber optics, which can be affected by the different paths that light rays can take through the fiber. One effective strategy to minimize modal dispersion is to use a smaller core diameter.

When the core of the fiber is smaller, it restricts the number of light modes that can propagate through it. In smaller cores, light is more likely to travel in a single, straight path rather than bouncing off the core walls at various angles. This limitation on the number of modes reduces the likelihood of overlapping light waves that can cause delays and distortions, which is the essence of modal dispersion.

The other options, while they might seem relevant, do not effectively reduce modal dispersion. Lowering the wavelength does not inherently solve the dispersion issue because it's more about how many paths or modes can exist within the fiber. Increasing the cladding diameter or using a larger core actually allows more light modes to be present in the fiber, which can increase modal dispersion rather than decrease it. Thus, using a smaller core is the best approach to addressing modal dispersion, making it the correct choice.