Multimode fiber is classified into five main categories—OM1, OM2, OM3, OM4, and OM5—each with distinct core sizes, bandwidths, and distance capabilities for short-range network applications.

Overview of Multimode Fiber

Multimode fiber (MMF) has a larger core diameter, typically 50 µm or 62.5 µm, allowing multiple light modes to propagate simultaneously. This makes it ideal for short-distance communication, such as within buildings, campuses, or data centers. MMF uses lower-cost light sources like LEDs or VCSELs and operates mainly at 850 nm and 1300 nm wavelengths. It is generally used for distances up to 550 meters, depending on the fiber type and data rate, whereas single-mode fiber is used for longer distances due to its smaller core and lower attenuation .

Multimode Fiber Categories

Key Points

• OM1 and OM2 are older standards, primarily used in legacy networks and are LED-optimized, making them less suitable for modern high-speed applications .
• OM3 and OM4 are laser-optimized multimode fibers (LOMMF), designed for VCSEL-based transceivers, supporting higher data rates and longer distances, making them the mainstream choice for modern data centers .
• OM5 extends OM4 capabilities by supporting shortwave wavelength division multiplexing (SWDM), allowing multiple wavelengths over a single fiber pair, which increases capacity without adding more fibers .
• All multimode fibers are backwards compatible with lower-speed applications, but high-speed standards like 40G and 100G Ethernet are not supported by OM1 and OM2 .

Applications

Multimode fiber is widely used in:

• Enterprise networks for building backbone and horizontal cabling
• Data centers for high-speed server interconnects
• Campus networks for short-range connectivity
• Specialized equipment like fiber optic spectroscopy or laser welding where high optical power is needed . Understanding these categories helps in selecting the right fiber type for cost-effective, high-performance network design, ensuring compatibility with current and future data rates.