Multimode fiber uses wavelengths of

Multimode fiber typically operates at 850 nm and 1300 nm, using LEDs or VCSELs for short- to medium-distance data transmission.

Standard Wavelengths

Multimode fiber (MMF) is designed to operate primarily at 850 nm and 1300 nm wavelengths, which are in the near-infrared spectrum. These wavelengths are chosen because they balance low attenuation in the fiber with the ability to use cost-effective light sources such as LEDs and VCSELs (Vertical-Cavity Surface-Emitting Lasers) for data transmission. The 850 nm wavelength is most common for short-distance links, while 1300 nm is used for slightly longer distances within buildings or campus networks.

Light SourcesLEDs: Broad emission spectrum, suitable for 850 nm operation, ideal for lower-cost, short-range applications.

VCSE

Ls: Narrower emission spectrum, more efficient, and commonly used in modern MMF systems, especially for OM3, OM4, and OM5 fibers.

Fiber Types and Wavelength Compatibility

Multimode fibers are classified as OM1, OM2, OM3, OM4, and OM5, with differences in core size, modal bandwidth, and optimized wavelength performance: OM1: 62. 5 µm core, typically uses 850 nm LED sources. OM2: 50 µm core, supports 850 nm and 1300 nm.

OM3/OM4: 50 µm core, optimized for laser-based VCSELs at 850 nm, supporting higher data rates (up to 100 Gbps) over distances up to 550 meters. OM5: 50 µm core, designed for shortwave wavelength-division multiplexing (SWDM), supporting multiple wavelengths from 850 nm to 940 nm for higher aggregate bandwidth.

Performance Considerations

The choice of wavelength affects attenuation, modal dispersion, and maximum transmission distance: 850 nm: Lower attenuation for short distances, widely used in data centers. 1300 nm: Slightly higher attenuation but reduced modal dispersion, suitable for longer intra-building links. Multiple wavelengths (OM5 SWDM): Allow simultaneous transmission of multiple signals over a single fiber, increasing capacity without additional cabling.

Summary

Multimode fiber wavelengths are carefully selected to optimize cost, performance, and distance. 850 nm and 1300 nm remain the standard, with modern fibers like OM5 enabling multi-wavelength operation for high-speed, short-reach applications. Choosing the correct wavelength and fiber type ensures reliable, high-bandwidth communication in enterprise and data center networks.