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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