What is the specified attenuation level for multimode fiber

Multimode fiber attenuation typically ranges from 2. 0–3. 5 dB/km at 850 nm and 0.

8–1. 5 dB/km at 1300 nm, depending on the fiber type (OM1–OM5) and wavelength. Standard Attenuation by Fiber TypeMultimode fibers are graded-index fibers standardized as OM1, OM2, OM3, OM4, and OM5, with attenuation values specified for the two primary wavelengths used in LAN and data center applications: 850 nm and 1300 nm.

OM1 (62. 5 µm core): 850 nm: ~3. 5 dB/km1300 nm: ~1.

5 dB/kmTypically used for legacy 1G Ethernet and short 10G links. OM2 (50 µm core): 850 nm: ~3. 0 dB/km1300 nm: ~1.

0 dB/kmSupports 1G Ethernet up to 550 m and 10G Ethernet up to 33 m under standard conditions. OM3 (50 µm core, laser-optimized): 850 nm: ~3. 0 dB/km1300 nm: ~1.

0 dB/kmDesigned for 10G, 40G, and 100G Ethernet over distances up to 300 m (10G) and 100–150 m (40/100G) using VCSELs. OM4 (50 µm core, laser-optimized, higher bandwidth): 850 nm: ~2. 6 dB/km1300 nm: ~0.

8 dB/kmSupports 10G Ethernet up to 550 m and 40/100G Ethernet up to 150 m. OM5 (50 µm core, wideband multimode): 850–950 nm: ~2. 6 dB/km1300 nm: ~0.

8 dB/kmOptimized for short-wavelength division multiplexing (SWDM) and backward compatible with OM4, supporting multi-wavelength systems.

Key Considerations

Wavelength Dependence: Attenuation is higher at 850 nm than at 1300 nm due to material absorption and scattering characteristics.

Laser-

Optimized Fibers: OM3, OM4, and OM5 are designed for VCSEL sources, providing lower effective attenuation and higher modal bandwidth compared to legacy OM1/OM2 fibers. Installation Factors: Actual attenuation can be affected by bending, splicing, and connector quality. Bend-insensitive fibers reduce macro-bending losses, especially in OM3–OM5 types.

Standards Compliance: ISO/IEC 11801 and TIA/EIA-568 define the attenuation and bandwidth requirements for each MMF type, ensuring interoperability across network equipment. In summary, multimode fiber attenuation standards vary by fiber type and wavelength, with modern laser-optimized fibers (OM3–OM5) offering lower attenuation and higher bandwidth for high-speed Ethernet applications, while legacy fibers (OM1/OM2) have higher attenuation and are suitable only for shorter distances.