Final answer:
Modal dispersion refers to the smearing of light pulses in an optical fiber due to different propagation speeds of various modes. To avoid it, use single-mode fibers and consider using graded-index fibers and maintaining a stable temperature.
Step-by-step explanation:
In the context of physics, modal dispersion refers to the spreading out or smearing of light pulses in an optical fiber due to the different propagation speeds of various modes or paths taken by light. This can result in a decrease in the quality and reliability of the transmitted signal.
To avoid modal dispersion, it is important to use single-mode fibers instead of multi-mode fibers. Single-mode fibers have a smaller core size, allowing only one mode of light to propagate through the fiber. This eliminates the issue of different modes arriving at different times and reduces dispersion.
In addition to using single-mode fibers, other methods to reduce modal dispersion include using graded-index fibers and keeping the fiber temperature stable.