What is the multimode and length of a 40G optical fiber

40G Ethernet over multimode fiber typically uses OM3, OM4, or OM5 fiber, with maximum distances of 100–150 meters depending on the fiber type.Fiber Types for 40GOM3 (50/125 µm laser-optimized multimode fiber): Supports 40G Ethernet up to 100 meters using 850 nm VCSEL transceivers .OM4 (50/125 µm enhanced laser-optimized multimode fiber): Extends 40G Ethernet reach to 150 meters at 850 nm .OM5 (Wideband multimode fiber, 50/125 µm): Designed for Short Wavelength Division Multiplexing (SWDM), OM5 also supports 40G Ethernet up to 150 meters, with additional benefits for multi-wavelength 100G and 400G applications .Key CharacteristicsCore diameter: 50 µm for OM3, OM4, and OM5, allowing multiple light modes to propagate simultaneously .Wavelength: 850 nm is standard for 40G VCSEL transceivers. OM5 additionally supports 850–953 nm for SWDM applications .Application: Short-reach data center links, typically within the same building or campus .Summary TableFiber TypeCore DiameterMax 40G DistanceNotesOM350 µm100 mStandard laser-optimized MMFOM450 µm150 mEnhanced bandwidth for longer reachOM550 µm150 mSupports SWDM for multi-wavelength 40G/100GFor most modern data centers, OM4 or OM5 is preferred for 40G links due to their higher bandwidth and extended reach, while OM3 remains suitable for shorter connections .