OM3 Fiber Cable: The Standard Inside the Building
Quick answer / TL;DR: Short answer: OM3 supports 10G to 300 m, 40G and 100G to about 100 m with MPO connectors, and 1G far beyond that. Choose OM4 when you need 400 m at 10G or 150 m at 40G, and single mode when the run leaves the building.
Fiber cords: two connector families, two fiber types, three polish options.OM3 is a laser-optimized 50 micron multimode fiber rated at 2000 MHz-km. It carries 10G to 300 metres and higher rates over shorter distances.
It remains the default choice for in-building backbone because the optics are inexpensive.
Reach by Speed
| Speed | OM3 | OM4 |
|---|
| 1G | 550 m | 550 m |
| 10G | 300 m | 400 m |
| 40G | 100 m | 150 m |
| 100G | 100 m | 150 m |
The 40G and 100G figures assume parallel optics over an MPO cable, not a duplex pair.
What Makes It Laser Optimized
- Controlled core index profile
- Consistent bandwidth at 850 nm
- Aqua jacket as the usual colour code
- Compatible with OM4 patch cords in one direction
Mixing OM3 and OM4 is permitted, but the link performs to the lower grade. There is no upgrade in one direction.
Real-World Applications
A floor-to-floor backbone in an office building with runs under 250 m is the classic OM3 case. A data hall being built for 100G at 150 m should specify OM4 now, because relocating cable later costs many times the difference in cable price.
Standards and Verification
| Reference | Relevance |
|---|
| ISO/IEC 11801 | OM3 category definition |
| TIA-492AAAC | Fiber specification |
| IEEE 802.3 | Reach by Ethernet rate |
Actual attenuation for a delivered cable is not provided in the knowledge base. Ask for the factory test report per reel.
Practical Notes
Record the fiber type at every patch panel. A later technician who assumes OM4 will plan a 400 m link that the installed OM3 cannot carry.
Related reading: fiber cable — blogs/news/fiber-cable
Related reading: om3 lc fiber patch — blogs/news/om3-lc-fiber-patch
Related reading: powered fiber cable — blogs/news/powered-fiber-cable
Frequently Asked Questions
How far does OM3 go at 10G?
300 metres.
Is OM3 obsolete?
No. It is still widely deployed for 10G in-building.
Can OM3 do 100G?
Yes, to about 100 m using MPO parallel optics.
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