Effective modal bandwidth (EMB), or how much data a certain fiber can send at a certain wavelength, is one of the most important characteristics about multimode fibers. EMB is measured in Megahertz over 1 Kilometer, or MHz/km. For example, OM3 fiber has an EMB of 2000 MHz/km and OM4 fiber has an EMB of 4700 MHz/km, therefore maximum distance for transporting 10G Ethernet over OM3 fiber is 300 meters and over OM4 fiber it is 400 meters.