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g/av • Posted by u/fiber_fred •

Best practices for fiber runs in a multi-building campus — OM3 vs OM4?

Laying out fiber infrastructure for a new 5-building campus, max run between buildings about 280 meters. We'll be running 10Gb Ethernet now with plans to upgrade to 25Gb or 40Gb in the future.

OM3 is significantly cheaper than OM4 for a run this size. But OM4 gives more headroom for 40Gb applications. At 280 meters, does OM4 matter, or is OM3 more than adequate?

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u/fiber_splicer_faye •

Also consider OM5 (wide band multimode) if you want maximum future-proofing for SWDM4 applications. The price delta between OM4 and OM5 is smaller than it used to be. At 280m, OM5 gives you 100Gb/SWDM4 headroom you won't get from OM3 or OM4.

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u/cat6_carlos •

OM4 supports 10Gb to 550m vs OM3's 300m limit. At 280m you're within OM3 spec for 10Gb but at the edge of OM3 for 40Gb/SWDM4 (which is also limited to ~240m on OM3). If 40Gb is a realistic future scenario, spend the money on OM4 now — you won't be re-pulling fiber in 5 years.

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u/rack_and_stack_rob •

Don't forget conduit fill and future pulls. Whatever fiber type you choose, install in innerduct with pull tape and leave significant slack at both ends. The cable type is one decision; making it re-pullable without a construction project is equally important.

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