What is the key disadvantage of using multimode fiber in long-distance communications?

The key disadvantage of using multimode fiber in long-distance communications is primarily due to signal distortion caused by modal dispersion. Multimode fiber allows multiple light modes to propagate through the core simultaneously. However, because these modes travel at different speeds, they can arrive at the destination at different times. This phenomenon, known as modal dispersion, can lead to signal overlap and distortion, which deteriorates the quality of the transmitted data over long distances.

As communication distances increase, the effects of modal dispersion become more pronounced. In practical terms, this means that multimode fiber is not suitable for long-distance applications where data integrity and signal clarity are critical. It is generally better to use single-mode fiber for these scenarios, as it supports only one mode of light propagation, resulting in significantly less dispersion and allowing signals to travel much farther without degradation.

Maintaining high fidelity in data transmission is essential, especially in environments where bandwidth and speed are priorities, such as telecommunications and data centers, further emphasizing the limitation of multimode fibers in long-distance applications.