FOA Guide

The Fiber Optic Association - Tech Topics

Fiber Optic Cable Plant Nomenclature
Multimode Premises Cable Plants

Types of MM Fiber
Multimode fiber has been manufactured in many sizes and types over the history of fiber optics. Here is a listing on the types available and most widely used.

 Fiber Types and Typical Specifications

 Multimode Graded-Index
 Core/Cladding (OMx refers to TIA/ISO types, to ITU) Attenuation @850/1300 nm, Typical (TIA*) Bandwidth @850/1300 nm  Applications/Notes
 50/125 microns (OM2, G.651.1)   3/1 dB/km (3.5/1.5 dB/km) 500/500 MHz-km  Laser-rated for GbE LANs
 50/125 microns (OM3, G.651.1)   3/1 dB/km (3.5/1.5 dB/km) 2000/500 MHz-km  Optimized for 850 nm VCSELs
 50/125 microns (OM4, G.651.1)**   3/1 dB/km (3.5/1.5 dB/km) 3600/500 MHz-km  Optimized for 850 nm VCSELs, higher speed for 10 GB/s and above
 62.5/125 microns (OM1)  3/1 dB/km (3.5/1.5 dB/km) 200/500 MHz-km  LAN fiber pre-GB/s networks
 62.5/125 microns (FDDI grade)  3/1 dB/km 160/500 MHz-km  LAN fiber from FDDI network specification
 100/140 microns  3/1 dB/km 150/300 MHz-km  Obsolete
 85/125 microns  3/1 dB/km 200/400 MHz-km  Rare, obsolete

Multimode Step-Index
 Core/Cladding Attenuation @850 nm Bandwidth @850 nm  Applications/Notes
 200/240 microns, usually PCS (plastic-clad silica) or HCS (hard-clad silica) types  4-6 dB/km  50 MHz-km  Slow LANs & links

POF (plastic optical fiber)
 Size  Attenuation @ 650 nm  Bandwidth  @ 650 nm  Applications/Notes
 1 mm (many other sizes available)  ~ 1 dB/m  ~5 MHz-km  Short Links & Cars

*TIA specifications are worst-case specifications for manufacturing fiber
** Specifications are being developed for a version of OM4 fiber that will support VCSEL-based WDM systems in the wavelength range of 850-950nm for network speeds >10G.

Since the introduction of Gigabit Ethernet, we've seen premises cabling, designed to carry gigabit and 10 gigabit (and faster) traffic using 850 nm VCSEL (laser) transmitters, moving toward standardization on 50/125 laser-optimized fiber (now often called OM3/OM4 fiber for it's international standards designation) often with LC connectors to match the manufacturers' standard for VCSEL transceivers. OM3 cabling even has it's own color, aqua, specified in TIA-598.
If you are planning, designing, installing or using high speed premises fiber optic networks,  you should probably be recommending and using OM3 or OM4 fiber and LC connectors. Within the industry, this is becoming a "de facto" standard. One big advantage of using a full OM3/OM4 cabling standard is that the cabling is easily identifiable by the aqua color and when LC connectors are used instead of ST or SC connectors, it cannot be interconnected with legacy cabling, especially 62.5/125 fiber which causes large mismatched fiber losses.

Using this nomenclature does not  specify a type of cable. Unlike Category-rated UTP, fiber optic cable is available in several types (zipcord, distribution or breakout) to allow choosing a cable for the installation, saving space, weight, and, since numerous links can be combined into one multifiber cable, installation costs.

The FOA is encouraging all FOA-Approved schools to adopt this nomenclature in their training. We've added this recommendation to the FOA User's Page.
Here is an example of the "OM3 Cabling" spec for designers to use in documentation:
The fiber optic cable plant will be type OM3 (or OM4) cabling, using laser optimized (OM3 or OM4) fiber in a cable with aqua colored jacket, terminated with LC type connectors and mating adapters all colored aqua. Individual fiber cable runs will be specified by number of fibers and cable type (riser, plenum, indoor-outdoor, etc.) required by the actual installation.

Here is a table of recommended nomenclature for all fiber optic cabling types to help specify a cable plant.

Cabling System Name Fiber Type Connector Type Cable Type (Premises, + fiber count)
OM4 OM4 - 50/125 laser optimized OM4 - (default LC)
OM4/ST - ST connector
OM4/SC - SC connector
OM3 OM3 - 50/125 laser optimized OM3 - (default LC)
OM3/ST - ST connector
OM3/SC - SC connector
OM2 OM2 - 50/125 OM2/ST - ST connector
OM2/SC - SC connector
OM2/LC - LC connector
OM1 OM1 - 62.5/125 OM1/ST - ST connector
OM1/SC - SC connector


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