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OM1, OM2, OM3, OM4, OM5 and OS1, OS2 Fiber

Fiber Testing Best Practices

In ANSI/TIA-568.3-D, 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-568.3-D 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

OM5 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 avoid optimistic results.

To most users, the following table may be of more benefit:

 

1000BASE-SX

10GBASE-SR

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

400 m*

150 m

150 m

OM5 Not specified 400 m* 150 m 150 m

* The IEEE in conjunction with the TIA is supporting 10GBASE-SR to 400 m over OM4.

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-568.3-D. 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

2.4 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

2.9 dB

1.5 dB

1.5 dB

OM5 Not specified 2.9 dB 1.5 dB 1.5 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

3.0 dB/km

1.5 dB/km

 

 

OM4*

3.0 dB/km

1.5 dB/km

 

 

OM5 3.0 dB/km 1.5 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)

 

While OM5 has similar performance values to OM4 for Insertion Loss and Distances supported, it has a special characteristic that differentiates it. OM5 fiber is designed to be used at wavelengths beyond 850 nm, specifically, 880 nm, 910 nm, and 940 nm. This means that it can support four simultaneous transmissions with Wave Division Multiplexing. There is an attenuation value for the 953 nm wavelength, 2.3 dB per KM. Field testing of OM5, however, only needs to be done at 850 and 1300 nm wavelengths.

 

* 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.


IMPORTANT:
When you setup your DSX CableAnalyzer Cable Type for fiber, 
 
            Setup of DTX CableAnalyzer Cable Type
 
it is important to make sure you select the fiber with the correct modal bandwidth. It will not affect the outcome of your TIA or ISO/IEC loss length test, but it will affect what shows up at the bottom of the test report in LinkWare for Network Compliant Standards.

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Author: Adrian Young

Creation Date: 2014-02-28

Last Modified: 2014-02-28