Why is single-mode fiber preferred for long-distance transmission?

Single-mode fiber is preferred for long-distance transmission primarily because it supports only one mode of light. This characteristic significantly reduces modal dispersion, which is the spreading of light pulses over time. Since single-mode fiber allows only a single path or mode for the light to travel, it maintains signal integrity over longer distances more effectively than multi-mode fiber, which can suffer from multiple paths of light overlapping and causing interference.

The design of single-mode fiber typically involves a smaller core diameter compared to multi-mode fiber, which is advantageous for reducing the number of modes and thus the potential for dispersion. For long-distance communication, minimizing signal loss and maintaining clarity is crucial, making this design a practical choice for high-bandwidth and long-range data transmission needs.

While other options, such as light weight, installation ease, and cost, may have some relevance, they do not pertain directly to the primary reason for choosing single-mode fiber for long-distance applications. The defining feature of supporting only one mode is what truly underpins its effectiveness in this context.