What is the maximum speed supported by multimode fiber

Multimode fiber can support speeds up to 400 Gbps using OM5 fiber with wavelength-division multiplexing (WDM) over short distances.

Overview of Multimode Fiber Speeds

Multimode fiber (MMF) is designed for short- to medium-range data transmission, typically inside buildings, data centers, or campus networks. The maximum speed depends on the fiber type, core size, and optical technology used. Standard multimode fibers are classified as OM1, OM2, OM3, OM4, and OM5, with increasing bandwidth and distance capabilities .

• OM1 (62.5 µm core): Supports up to 10 Gbps for distances up to 33 meters, commonly used for 100 Mbps Ethernet .
• OM2 (50 µm core): Supports 10 Gbps up to 82 meters, typically used for 1 Gbps Ethernet .
• OM3 (50 µm, laser-optimized): Supports 10 Gbps up to 300 meters, 40 Gbps and 100 Gbps up to 100 meters .
• OM4 (50 µm, laser-optimized): Supports 10 Gbps up to 400–550 meters, 40 Gbps and 100 Gbps up to 150 meters .
• OM5 (50 µm, wideband multimode): Designed for short-range WDM applications, supporting 40 Gbps, 100 Gbps, and even 400 Gbps using multiple wavelengths over distances similar to OM4 .

Enabling Technologies

High-speed multimode fiber relies on VCSELs (Vertical-Cavity Surface-Emitting Lasers), which can modulate light at rates exceeding 10 Gbps, unlike LEDs that are limited to around 622 Mbps . For speeds beyond 100 Gbps, wavelength-division multiplexing (WDM) is used, particularly with OM5 fiber, allowing multiple data channels on different wavelengths to transmit simultaneously .

Practical Considerations

• Distance limitations: Higher speeds reduce the maximum transmission distance due to modal dispersion. For example, 400 Gbps over OM5 is feasible only for short-range data center links.
• Backward compatibility: OM4 and OM5 fibers are compatible with OM3 equipment, allowing gradual upgrades.
• Connector types: LC connectors are standard for most high-speed multimode installations, while MPO/MTP connectors are used for parallel optics in 40G, 100G, and 400G links .

Summary

The highest practical speed for multimode fiber is 400 Gbps, achievable with OM5 fiber using WDM over short distances in data centers. For conventional Ethernet applications, OM4 supports up to 100 Gbps, while OM3 supports up to 100 Gbps over shorter distances. The choice of fiber type depends on the required speed, distance, and network design constraints .