What is single mode fiber?

Single-mode fiber is a type of fiber optic cable through which only one light signal can travel at a time.
Because single-mode fiber is more resistant to attenuation than multi-mode fiber, it can be used in significantly longer cable runs.
The core of a single-mode fiber is normally 9 microns wide. A micron is one millionth of a meter.
Single-mode fiber can support Gigabit Ethernet over distances as long as 10 kilomters.
The opposite of single-mode fiber is multi-mode fiber.