What is Single-Mode Fiber?
Single-mode fiber has a core diameter in 10 micron to allow only single mode of light to propagate. This eliminates the main limitation to bandwidth and modal dispersion. However,the small core of a single-mode fiber makes coupling light into the fiber more difficult, and thus expensive lasers must be used as light sources. The main limitation to the bandwidth of a single-mode fiber is material (chromatic) dispersion. Laser sources must also be used to attain high bandwidth, because LEDs emit a large range of frequencies, and thus material dispersion becomes significant. Single-mode fiber is capable of supporting much longer segment lengths than multi-mode fiber. Segment lengths of 5000 meters and beyond are supported at all Ethernet data rates through 1 Gbps. Single-mode fiber is significantly more expensive to deploy than multi-mode fiber because of the high laser equipment cost.
