Bandwidth of multimode optical cables

Multimode optical fibers support high data rates over short distances, with bandwidth varying by fiber type: OM1 (200 MHz·km) to OM5 (4700 MHz·km at 850 nm).

Overview of Multimode Fiber

Multimode fiber (MMF) has a larger core diameter (50–62. 5 µm) than single-mode fiber, allowing multiple light modes to propagate simultaneously. This makes it ideal for short-range, high-bandwidth applications such as enterprise networks, campus backbones, and data centers.

MM

F is generally paired with LEDs or VCSELs as light sources, which are cost-effective and suitable for high-speed transmission over limited distances.

Fiber Types and Bandwidth

Multimode fibers are classified according to ISO/IEC 11801 standards into OM1, OM2, OM3, OM4, and OM5, with each type offering different modal bandwidths and maximum transmission distances: OM1 (62. 5 µm core): Modal bandwidth ~200 MHz·km; supports 10 Mbit/s to 1 Gbit/s Ethernet; 10G Ethernet up to 33 meters; uses LED sources; orange jacket. OM2 (50 µm core): Modal bandwidth ~500 MHz·km; supports 1G Ethernet and limited 10G Ethernet up to 82 meters; LED sources; orange jacket.

OM3 (50 µm core, laser-optimized): Modal bandwidth ~2000 MHz·km; supports 10G Ethernet up to 300 meters, 40G/100G Ethernet up to 100 meters; VCSEL sources; aqua jacket. OM4 (50 µm core, laser-optimized): Modal bandwidth ~4700 MHz·km; supports 10G Ethernet up to 400 meters, 40G Ethernet up to 150 meters, 100G Ethernet up to 100 meters; improved attenuation and dispersion; aqua jacket. OM5 (50 µm core, wideband MMF): Modal bandwidth 4700 MHz·km at 850 nm and 2470 MHz·km at 953 nm; designed for short-wavelength division multiplexing (SWDM); supports 40G, 100G, and 400G SWDM links; lime green jacket.

Bandwidth Considerations

The effective bandwidth of multimode fiber depends on: Core size and fiber type: Larger cores (OM1) have lower bandwidth due to modal dispersion, while laser-optimized fibers (OM3–OM5) reduce dispersion and increase bandwidth. Distance: Bandwidth decreases with longer distances; for example, OM3 supports 10G Ethernet up to 300 meters but only 40G/100G up to 100 meters. Light source: LEDs have slower modulation rates (~622 Mbit/s), limiting bandwidth, whereas VCSELs enable higher-speed transmission.

Practical ApplicationsOM1/OM2: Legacy networks, short-distance 1G Ethernet, older campus installations. OM3/OM4: Modern enterprise networks, data centers, 10G–100G Ethernet, cost-effective for short-range high-speed links. OM5: Emerging high-speed networks using SWDM, future-proofing for 400G and beyond.

In summary, multimode fiber bandwidth ranges from 200 MHz·km (OM1) to 4700 MHz·km (OM4/OM5), with higher-speed, laser-optimized fibers enabling longer distances and higher data rates for modern network applications.