What is the difference between multimode and single mode fiber?

Multimode fiber typically has a core diameter of 50 to 300 microns which is larger than single mode fiber. Single mode fiber usually has a core diameter around 8.5 microns. Multimode fiber allows light to travel through multiple paths to reach its destination and is used for many short distance (< 5 Km) applications. Single mode fiber however, allows only one path for light to propagate and it is used for much longer transmission distances.