OM3 and OM4 fibers are backward compatible. Connectors, transceivers, and equipment designed for one will generally work with the other, provided all components use the same core size (50/125 µm). However, the overall performance will be limited to the lowest-rated component in. ISO/IEC 11801 defines the OM1, OM2, OM3, OM4, and OM5 types of multimode fiber. It also lists the key technical requirements for each type. Two of the most widely deployed laser-optimized multimode fibers are OM3 and OM4, both designed to support high-speed data transmission. OM3 and OM4 are both multimode fiber types that are widely used in data centers and enterprise networks. While they share similarities, they also have distinct differences that can impact their use in a network.