1. OM1 refers to multimode optical fibers with a core diameter of 850/full injection bandwidth exceeding 200/. km for 5 Oum or 62.5um fibers;

2. OM2 refers to multimode optical fibers with a core diameter of 850/full injection bandwidth exceeding 500/. km for 50um or 62.5um fibers;

3. OM3 is a 50um core diameter multimode fiber optimized for 850nm laser. In 10Gb/s Ethernet using 850nm VCSEL, the fiber optic transmission distance can reach 300m;

4. OM4 Fiber Patch Cords is an upgraded version of OM 3 multimode fiber, with fiber transmission distances up to 550 meters.
link:https://www.fibertelcom.com/fiber-patch-cords/om4-fiber-patch-cables.html