What is the primary disadvantage of multi-mode fiber in long-distance applications?

The primary disadvantage of multi-mode fiber in long-distance applications is the higher modal dispersion, which reduces signal quality. Multi-mode fiber allows multiple light modes (or pathways) to propagate through the core, but this leads to variations in travel times for different modes. When the light signals travel over long distances, these variations can cause the signals to spread out and become indistinguishable from one another upon reaching the receiver. This phenomenon results in a degradation of the signal quality and limits the effective data transmission distance compared to single-mode fiber, which allows only one mode of light to travel, thereby minimizing dispersion and enabling longer distance communication with better signal integrity.