How many specifications are there for multimode optical fiber

Multimode optical fiber (MMF) is standardized by ISO/IEC 11801 and ITU-T G.651.1, with core diameters of 50–62.5 µm, supporting multiple light modes for short-distance, high-speed data transmission.Core and Cladding

Multimode fibers have a larger core diameter than single-mode fibers, typically 50 µm or 62.5 µm, surrounded by a cladding of 125 µm. The core allows multiple light modes to propagate simultaneously, which increases launch tolerance but introduces modal dispersion, limiting maximum transmission distance. MMF can have either a step-index profile (sharp core-cladding transition) or a graded-index profile (gradual transition), with graded-index fibers reducing modal dispersion and extending effective propagation distances .

Fiber Types and Standards

MMF is classified into five main types according to ISO/IEC 11801 and TIA standards:

• OM1: 62.5/125 µm, LED-optimized, orange jacket, supports 1G Ethernet up to 275 m and 10G Ethernet up to 33 m. Standardized in 1989 .
• OM2: 50/125 µm, LED-optimized, orange jacket, supports 1G Ethernet up to 550 m and 10G Ethernet up to 33 m. Standardized in 1998 .
• OM3: 50/125 µm, laser-optimized for VCSELs, aqua jacket, supports 10G Ethernet up to 300 m, 40/100G up to 100 m. Standardized in 2003 .
• OM4: 50/125 µm, laser-optimized, aqua jacket, supports 10G Ethernet up to 550 m, 40/100G up to 150 m. Published in 2009 (TIA-492-AAAD), .
• OM5: 50/125 µm, wideband multimode fiber (WBMMF), lime green jacket, optimized for shortwave wavelength division multiplexing (SWDM), supporting multiple wavelengths for higher aggregate bandwidth .

Wavelength and Modal Bandwidth

MMF typically operates at 850 nm and 1300 nm wavelengths. Modal bandwidth, measured in MHz·km, defines the fiber's capacity to transmit data without significant signal degradation. OM1 and OM2 are LED-optimized with lower bandwidth, while OM3–OM5 are laser-optimized, providing higher bandwidth suitable for modern high-speed networks .

Standards and Compliance

• ITU-T G.651.1: Defines the most widely used forms of multimode optical fiber .
• ISO/IEC 11801: Specifies OM1–OM5 classifications, modal bandwidth, and performance requirements .
• TIA-492-AAAD: Defines OM4 fiber and its performance for high-speed Ethernet applications .

Applications

MMF is primarily used for short-distance communication, such as within buildings, campuses, and data centers. It is cost-effective due to compatibility with LED and VCSEL transceivers. Typical applications include 10G/25G/40G/100G Ethernet, backbone cabling, and high-speed interconnects in enterprise networks .

Summary

Multimode optical fiber is defined by core size, modal bandwidth, wavelength, and fiber type, with standards ensuring interoperability and performance. OM3 and OM4 dominate modern deployments, while OM1 and OM2 remain in legacy networks. OM5 introduces wideband capabilities for future high-speed, multi-wavelength applications. Compliance with ITU-T G.651.1, ISO/IEC 11801, and TIA standards ensures reliable, high-performance short-range optical communication.