What is the primary difference between single-mode and multi-mode fibers?

The primary difference between single-mode and multi-mode fibers lies in their capability to transmit light. Single-mode fibers allow only one light path, or mode, to travel through the core of the fiber. This is achieved because single-mode fibers have a very small core diameter, typically around 8 to 10 micrometers, which restricts the light to a single path. As a result, single-mode fibers are ideal for long-distance communication as they minimize modal dispersion, enabling higher bandwidth over greater distances.

In contrast, multi-mode fibers have a larger core diameter, usually around 50 to 62.5 micrometers, allowing multiple light paths or modes to travel simultaneously. This can lead to modal dispersion, where different paths of light arrive at different times, which can limit the distance over which multi-mode fibers can effectively transmit signals without degradation.

Understanding this fundamental difference is crucial for selecting the appropriate type of fiber optic cable based on the application, particularly when considering factors such as distance, bandwidth, and environmental conditions in communication networks.