Understanding Multimode - Fiber Types

Part 1

When I first started in the fiber telecom industry, multimode optical fiber was simple with just one option available (62.5/125um core size). It wasn’t long before a second option came around with a smaller core size of 50/125um offering extended transmission distance and bandwidth. Today, there are 4 multimode cabling standards as defined by ISO/IEC 11801 regarding Fiber Optic Interconnect systems. It is important to know and understand the benefits of each multimode fiber type when designing or expanding a fiber network. It can save you money and potential hassles later in the installation.

All fiber technicians and network designers should know that singlemode fiber is most often reserved for long distance networks and high bandwidth trunk lines while multimode fiber is most commonly found in premise or short distance campus networks. Improvements in multimode fiber design in the last decade have expanded the distance and bandwidth restriction that once prevented it from meeting network demands. We now have 4 industry standard multimode fiber types which include OM1, OM2, OM3 and OM4 cabling.

OM1 is the classic large core 62.5/125um multimode fiber cable and in premise networks, designated with an orange jacketing. OM2 is the original 50/125um reduced core cable and in premise networks, designated with a red/orange jacketing. OM3 and OM4 are the new kids in the neighborhood and are the only multimode fiber cable types capable of meeting the IEEE 802.3ba standard for 40GbE and 100GbE. Both types are often referred to as laser optimized. In a premise network, OM3 is designated with an aqua colored jacket while OM4 is designated with a violet colored jacketing. If you are ever unsure about which type of multimode cable you are working on, look for printing on the jacketing that specifies the core/cladding diameter and fiber type (OM1, OM2, OM3 and OM4).

A table has been provided below from FNT outlining the different types of multimode fiber with each bandwidth and distance restrictions.

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Knowing and understanding the benefits of each multimode fiber type when designing or expanding a fiber network can save you money and potential hassels later in the installation.

Refer to the FNT Multimode chart below outlining the different types of fiber with bandwidth and distance restrictions.

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