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Maximum attenuation of multimode fiber

Fiber and communications infrastructure knowledge brief Published 22 Sep 2024

Use this reference to prepare product questions for BAGYOU FIBRE. Check interfaces, capacity, protection and installation requirements against the current product documentation.

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

6–1. 5 dB/km at 1300 nm, depending on fiber type (OM1–OM5) and laser optimization.

Attenuation Overview

Attenuation in multimode fiber (MMF) refers to the loss of optical power per unit length, usually expressed in dB/km. It is a critical factor in determining the maximum transmission distance for a given data rate and wavelength. Lower attenuation allows longer links without signal repeaters or amplifiers.

Typical Attenuation by Fiber TypeOM1 (62. 5 µm core, LED-optimized): 850 nm: ~3. 5 dB/km1300 nm: ~1.

5 dB/kmSuitable for 1G Ethernet up to 275 m and 10G Ethernet up to 33 m. OM2 (50 µm core, LED-optimized): 850 nm: ~3. 0 dB/km1300 nm: ~1.

0 dB/kmSupports 1G Ethernet up to 550 m and 10G Ethernet up to 33 m. OM3 (50 µm core, laser-optimized): 850 nm: ~3. 5 dB/km1300 nm: ~1.

0 dB/kmDesigned for VCSELs, supports 10G Ethernet up to 300 m, 40G up to 100 m, and 100G up to 100 m. OM4 (50 µm core, laser-optimized, higher bandwidth): 850 nm: ~3. 0 dB/km1300 nm: ~1.

0 dB/kmExtends 10G Ethernet to 400 m, 40G to 150 m, and 100G to 150 m. OM5 (50 µm core, wideband, SWDM-capable): 850–950 nm: similar attenuation to OM4 (~3. 0 dB/km at 850 nm)Supports multi-wavelength short-range multiplexing for 40G, 100G, and 400G applications.

Key Considerations

Wavelength Dependence: Attenuation is lower at 1300 nm than at 850 nm for all MMF types, but most modern data center applications use 850 nm VCSELs, making 850 nm attenuation the primary design factor.

Laser-

Optimized Fibers: OM3, OM4, and OM5 fibers are optimized for VCSELs, providing lower effective attenuation and higher modal bandwidth compared to older LED-optimized OM1 and OM2 fibers. Distance and Data Rate: The allowable link distance is determined by the total channel loss, which includes fiber attenuation, connector loss, and splice loss. Designers must ensure that the sum of these losses does not exceed the transceiver's power budget.

Standards Compliance: MMF attenuation requirements are defined by TIA-492AAAB/AAAC/AAAD and IEC 60793-2-10, ensuring interoperability and predictable performance across vendors.

Summary

For modern enterprise and data center networks, OM3, OM4, and OM5 fibers are preferred due to their lower attenuation and higher bandwidth, supporting high-speed Ethernet over longer distances. Attenuation values are typically 3. 0–3.

5 dB/km at 850 nm and 1. 0–1. 5 dB/km at 1300 nm, and these values are critical for calculating link budgets and ensuring reliable network performance.

Maximum attenuation of multimode fiber - BAGYOU FIBRE NETWORKS [PDF]

Maximum attenuation of multimode fiber

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Technical note

This reference is intended for preliminary fiber and communications infrastructure research. Optical interface, fiber type, port or core capacity, electrical input and output, enclosure protection, cooling, installation limits and applicable standards must be verified for the specific project.

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