FOA Tech Topics - Fiber Optic Cable Plant Nomenclature

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 of the types available and most widely used and their nomenclature. Generally fibers are standardized by each standards body so the nomenclature can be different for each. More on optical fiber nomenclature for fiber here.

Fiber Types and Typical Specifications
Multimode Graded-Index
Core/Cladding (OMx refers to TIA/ISO types, G.xxx 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
50/125 microns (OM5, G.651.1)	3/1 dB/km (3.5/1.5 dB/km)	3500/500 MHz-km	Optimized for WDM with VCSELs, in wavelength range 850-950nm
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 & Vehicles

*TIA specifications are worst-case specifications for manufacturing fiber

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 color codes.

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. OM5 fiber is a special version of OM4 specified for use in the full range of 850-950nm to allow wavelength division multiplexing with VCSELs.

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.

Here is an example of the "OM3 Cabling" spec for designers to use in documentation:
The fiber optic cable plant will be type OM3 cabling, using laser optimized OM3 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)
OM5	OM5 - 50/125 laser optimized	OM5 - (default LC) OM5/ST - ST connector OM5/SC - SC connector	Zipcord Distribution Breakout
OM4	OM4 - 50/125 laser optimized	OM4 - (default LC) OM4/ST - ST connector OM4/SC - SC connector	Same
OM2	OM2 - 50/125	OM2/ST - ST connector OM2/SC - SC connector OM2/LC - LC connector	Same
OM1	OM1 - 62.5/125	OM1/ST - ST connector OM1/SC - SC connector	Same

Color Codes

Fiber types are identified by color codes for cable jackets and/or connectors.

More information on fiber optic color codes.

More Information on Singlemode and Multimode fiber.

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