Classification of Multimode Fiber Optic Connectors

Multimode fiber optic connectors are classified according to ISO/IEC 11801 standards, with fibers categorized as OM1 through OM5, each supporting specific core sizes, bandwidths, and transmission distances, and using standardized connector types like ST, SC, LC, and MTP/MPO.

Multimode Fiber Classification

Multimode fibers (MMF) are designed for short-distance communication, typically within buildings or campuses, and have larger core diameters (50–62.5 µm) that allow multiple light modes to propagate simultaneously . The ISO/IEC 11801 standard defines five generations of multimode fiber:

• OM1: 62.5 µm core, LED light source, orange jacket, supports 10 Gb/s up to 33 m, mainly used in legacy 100 Mb/s and 1 Gb/s networks .
• OM2: 50 µm core, LED light source, orange jacket, supports 10 Gb/s up to 82 m, suitable for 1 Gb/s applications .
• OM3: 50 µm core, laser-optimized for VCSELs, aqua jacket, supports 10 Gb/s up to 300 m and 40/100 Gb/s up to 100 m .
• OM4: Enhanced laser-optimized 50 µm core, aqua jacket, supports 10 Gb/s up to 550 m and 40/100 Gb/s up to 150 m, backward compatible with OM3 .
• OM5: Wideband multimode fiber (WB-MMF), supports shortwave division multiplexing (SWDM) across 850–940 nm, enabling multiple wavelengths for 100G/200G/400G short-range applications .

Connector Types for Multimode Fiber

Multimode fibers use standardized connectors to ensure compatibility and performance. Common connector types include:

• ST (Straight Tip): Bayonet-style, widely used in legacy networks, suitable for multimode applications.
• SC (Subscriber Connector): Push-pull design, common in data centers and enterprise networks.
• LC (Lucent Connector): Small form factor, high-density applications, widely used with OM3/OM4 fibers.
• MTRJ (Mechanical Transfer Registered Jack): Duplex connector, compact, used in some LAN applications.
• MTP/MPO (Multi-Fiber Push-On/Pull-Off): High-density multi-fiber connectors, ideal for 40/100 Gb/s data center links.
• FC (Ferrule Connector): Screw-on type, less common in modern enterprise networks but still used in some industrial applications .

Standards and Compliance

All multimode fibers and connectors should comply with ISO/IEC 11801 and related industry standards, ensuring consistent performance, modal bandwidth, and interoperability across devices and transceivers . Laser-optimized 50 µm multimode fibers (LOMMF) are recommended for modern LAN and data center environments, particularly when using VCSEL-based transceivers for 10 Gb/s and higher speeds .

Practical Considerations

• Backward Compatibility: OM3 and OM4 fibers are backward compatible with OM1 and OM2 connectors, but older fibers may not support high-speed 40/100 Gb/s links .
• Color Coding: Fiber jackets are color-coded for easy identification: OM1/OM2 (orange), OM3/OM4 (aqua), OM5 (lime green), .
• Application Suitability: OM1/OM2 are mostly legacy; OM3/OM4 are standard for modern enterprise and data center networks; OM5 is emerging for high-speed SWDM applications . Understanding these classifications and connector standards is essential for designing reliable, high-performance multimode fiber networks that meet current and future data transmission requirements.