OM4 fiber is a laser-optimized, high bandwidth 50um multimode fiber. OM4 fiber is not a new fiber type. All major fiber manufacturers have been selling a fiber with an effective modal bandwidth (EMB) value equivalent to that specified by OM4 since 2005. The change is that there is now a standard that is specifically targeted at this product. Prior to the standardization of OM4, these higher bandwidth fibers were sold as a part of OM3.

OM3 and OM4 fiber are referred to as “laser-optimized” multimode fibers because they are specifically designed for optimum performance when used with low cost Vertical-Cavity-Surface-Emitting-Lasers (VCSELs).

OM4 fiber is designed to enhance the system cost benefits enabled by 850nm VCSELs for existing 1 Gb/s and 10 Gb/s applications as well as future 40 Gb/s and 100 Gb/s systems.

OM4 fiber supports Ethernet, Fibre Channel, and OIF applications, allowing extended reach upwards of 550 meters at 10 Gb/s for ultra long building backbones and medium length campus backbones.

:: Why Is It Called OM4?

Multimode fibers are identified by the OM (“optical mode”) designation as outlined in the ISO/IEC 11801 standard.

  • OM1, for fiber with 200/500 MHz*km overfilled launch (OFL) bandwidth at 850/1300nm (typically 62.5/125um fiber)
  • OM2, for fiber with 500/500 MHz*km OFL bandwidth at 850/1300nm (typically 50/125um fiber)
  • OM3, for laser-optimized 50um fiber having 2000 MHz*km effective modal bandwidth (EMB, also known as laser bandwidth), designed for 10 Gb/s transmission.
  • OM4, for laser-optimized 50um fiber having 4700 MHz*km EMB bandwidth designed for 10 Gb/s, 40 Gb/s, and 100 Gb/s transmission.

:: OM4 Fiber Standard

The TIA/EIA approved OM4 specification in its TIA-492AAAD in 2009. IEC’s document covering OM4 standard is IEC 60793-2-10 as fiber type A1a.3.

:: Bandwidth Comparison of OM1, OM2, OM3, and OM4 Fibers

The following table shows the bandwidth comparison among OM1, OM2, OM3 and OM4 fibers.

Multimode Fiber Bandwidth (MHz * km)
OM Designation TIA Fiber Standard Fiber Type
(um)
Overfilled Launch (OFL)
@850nm
Effective Modal Bandwidth (EMB)
@850nm
Overfilled Launch (OFL)
@1300nm
OM1 492-AAAA 62.5/125 200 n/s 500
OM2 492-AAAB 50/125 500 n/s 500
OM3 492-AAAC 50/125 1500 2000 500
OM4 492-AAAD 50/125 3500 4700 500

The following table and graph shows the maximum distance different multimode fibers can carry.

Applications Wavelength(nm) Maximum Channel Length (meters)
OM1 OM2 OM3 OM4
Fibre Channel
4 Gb/s 850 70 150 380 400
8 Gb/s 850 21 50 150 200
16 Gb/s 850 15 35 100 130
Ethernet
1 Gb/s 850 275 550 800 1100
10 Gb/s 850 33 82 300 550
40 & 100 Gb/s 850 n/s n/s 100 125
1 Gb/s 1300 550 550 550 550
10 Gb/s 1300 220
(10GBase-LRM)
300
(10Gbase-LX4)
220
(10GBase-LRM)
300
(10Gbase-LX4)
220
(10GBase-LRM)
300
(10Gbase-LX4)
220
(10GBase-LRM)
300
(10Gbase-LX4)

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