OM1, OM2, OM3, OM4 and OS1, OS2 Fibers
In ANSI/TIA-T568C.3, the TIA adopted the nomenclature for fiber found in the international standard
ISO/IEC 11801. The multimode fiber is prefixed with “OM” and the singlemode mode “OS”.
The new designation in ANSI/TIA-568-C.3 should alleviate some of the confusion associated with application
support distance issues. Each “OM” has a minimum Modal Bandwidth (MBW) requirement.
Minimum modal bandwidth MHz.km | ||||
Wavelength | Overfilled launch bandwidth | Effect laser launch bandwidth | ||
Fiber Type | Core diameter | 850 nm | 1300 nm | 850 nm |
OM1 | 62.5 µm | 200 | 500 | Not specified |
OM2 | 50 µm | 500 | 500 | Not specified |
OM3 | 50 µm | 1500 | 500 | 2,000 |
OM4 | 50 µm | 3500 | 500 | 4,700 |
Why two values? What’s the difference between overfilled and effective? Overfilled is with an LED source,
effective is with a VCSEL. New vs old. Loss length testing to ISO/IEC must be done with an LED and
should be done with an LED for TIA testing.
To most users, the following table may be of more benefit:
1000BASE-SX | 10GBASE-S | 40GBASE-SR4 | 100GBASE-SR10 | |
OM1 | 275 m | 33 m | Not specified | Not specified |
OM2 | 550 m | 82 m | Not specified | Not specified |
OM3 | Not specified | 300 m | 100 m | 100 m |
OM4 | Not specified | 500 m* | 150 m | 150 m |
* The IEEE has yet to officially give a distance for 10GBASE-S on OM4 fiber.
The distances are decided by the IEEE in 802.3, not the TIA or ISO/IEC cabling standards.
Some glass vendors say 500 m, but most are now quoting “up to 550 m”.
Cautionary note: In ANSI/TIA-568-B.3, the modal bandwidth of 62.5 µm fiber was 160 MHz.km,
not the 200 MHz.km found in the current ANSI/TIA-568-C.3. This change was done to harmonize with ISO/IEC 11801.
That would reduce the distance for 1000BASE-SX to 220 m and 10GBASE-S to 26 m.
There is also a loss limit associated with these distances too.
1000BASE-SX | 10GBASE-S | 40GBASE-SR4 | 100GBASE-SR10 | |
OM1 | 2.60 dB | 2.5 dB | Not specified | Not specified |
OM2 | 3.56 dB | 2.3 dB | Not specified | Not specified |
OM3 | 3.56 dB | 2.6 dB | 1.9 dB | 1.9 dB |
OM4 | Not specified | Not specified | 1.9 dB | 1.9 dB |
So in your design, you have to take into account BOTH distance and loss to ensure your application will work.
OM4 fiber needs a reduced fiber loss in order to support 100GBASE-SR10 to 150 m.
850 nm | 1300 nm | 1310 nm | 1550 nm | |
OM1 | 3.5 dB/km | 1.5 dB/km | ||
OM2 | 3.5 dB/km | 1.5 dB/km | ||
OM3 | 3.5 dB/km | 1.5 dB/km | ||
OM4* | 2.5 dB/km | 0.8 dB/km | ||
OS1 ISP | 1.0 dB/km | 1.0 dB/km | ||
OS1 OSP | 0.5 dB/km | 0.5 dB/km | ||
OS2 ISP | 1.0 dB/km | 1.0 dB/km | ||
OS2 OSP | 0.5 dB/km | 0.5 dB/km |
ISP = Inside plant, OSP = Outside plant (Applicable to TIA only)
* The values above for OM4 are taken from TIA-492AAAD. This is a minimum requirement. Some vendors are quoting 2.3 dB/km. Check with your vendor and
work with them carefully on the design of the fiber plant.
OM4 fiber will be added as a Fiber Type in the next release of DTX code due end Q2 2010