What operational principles differentiate single-mode and multi-mode fiber optic cables, and how do their structural variations impact transmission capabilities?

Q: What operational principles differentiate single-mode and multi-mode fiber optic cables, and how do their structural variations impact transmission capabilities?   A: Single-mode fiber optic cables feature an extremely narrow core diameter (typically less than 10 micrometers), enabling light to propagate in a direct, linear path with minimal signal dispersion. This design facilitates data transmission over distances exceeding 100 kilometers, making them ideal for long-haul telecommunications infrastructure. In contrast, multi-mode fibers incorporate a wider core that allows multiple light reflection pathways, resulting in greater modal dispersion and limiting effective transmission ranges to approximately 2 kilometers. Despite this distance constraint, multi-mode cables offer cost advantages and remain highly efficient for short-range applications such as data center interconnects, where their broader core simplifies light source alignment and reduces hardware expenses compared to single-mode alternatives. Both variants leverage total internal reflection to minimize signal loss, outperforming metallic conductors in bandwidth capacity (with fiber supporting up to 400 Gbps versus 1 Gbps for traditional copper Ethernet cables) while maintaining immunity to electromagnetic interference.