Technical parameters of ordinary multimode optical cables

Multimode optical fibers (MMF) are characterized by core size, modal bandwidth, attenuation, maximum transmission distance, and optical source type, with OM1 through OM5 standards defining their performance for different data rates and applications.Core Size and Fiber TypesMultimode fibers have larger cores than single-mode fibers, typically 50 µm or 62.5 µm, allowing multiple light modes to propagate simultaneously. The ISO/IEC 11801 standard classifies MMF into five generations:OM1: 62.5 µm core, LED source, legacy applications, supports 10G Ethernet up to 33 m.OM2: 50 µm core, LED source, supports 1G Ethernet and limited 10G up to 82 m.OM3: 50 µm core, laser-optimized for VCSELs, supports 10G/25G Ethernet up to 300 m, 40G/100G up to 100 m.OM4: Enhanced 50 µm core, higher bandwidth, supports 10G/25G Ethernet up to 550 m, 40G/100G up to 150 m.OM5: Wideband 50 µm core, supports short-wavelength division multiplexing (SWDM), modal bandwidth 4700 MHz·km at 850 nm and 2470 MHz·km at 953 nm, optimized for multi-wavelength 40G/100G/400G links .Bandwidth and AttenuationThe effective modal bandwidth (EMB) is a key parameter determining data rate and distance. Typical values:OM1: ~200 MHz·km at 850 nmOM2: ~500 MHz·km at 850 nmOM3: ~2000 MHz·km at 850 nmOM4: ~4700 MHz·km at 850 nmOM5: 4700 MHz·km at 850 nm, 2470 MHz·km at 953 nm Attenuation is usually measured in dB/km and varies with wavelength:850 nm: 2.5–3.5 dB/km1300 nm: 0.8–1.5 dB/km These parameters directly affect the maximum transmission distance for a given data rate .Optical SourcesLEDs: Used in OM1 and OM2, suitable for lower-speed, short-distance links.VCSELs: Used in OM3 and OM4, optimized for high-speed data center applications.SWDM lasers: Used in OM5 for multi-wavelength high-speed links .Maximum Transmission DistancesThe supported distances depend on fiber type and data rate:1G Ethernet: OM1 up to 275 m, OM2 up to 550 m10G Ethernet: OM1 up to 33 m, OM2 up to 82 m, OM3 up to 300 m, OM4 up to 550 m40G/100G Ethernet: OM3 up to 100 m, OM4 up to 150 m, OM5 optimized for SWDM links .SummaryWhen selecting a multimode optical cable, the core size, modal bandwidth, attenuation, optical source, and maximum distance are the primary model parameters. OM3 and OM4 are the most common for modern data centers, while OM5 is emerging for multi-wavelength high-speed applications. OM1 and OM2 remain in legacy networks but are generally unsuitable for 10G+ Ethernet. Proper selection ensures cost-effective, high-performance network deployment .