Fibre
OM4 vs OS2 — choosing fibre for office backbones
When multimode OM4 is enough inside a building, when OS2 single-mode is the safer backbone, and how hybrid designs usually look.
Fibre type is a long-lived decision. Cable cost is rarely the expensive part — optics, pathways and re-pulls are.
Short version
- OM4 (multimode): often suitable for shorter intra-building links (MDF↔IDF style) where distances stay within multimode application limits and SR-class optics are preferred.
- OS2 (single-mode): default for inter-building / campus, longer risers, or any path you do not want to outgrow when speeds rise.
- Hybrid: OS2 on campus/risers + OM4 only where distance is controlled inside rooms is a common pattern in industry guidance.
Vendor and integrator guides consistently warn that as Ethernet rates climb, multimode reach shrinks — distance is physics, not marketing.
Cost honesty
OS2 cable is often competitive with OM4; transceiver budgets differ by design. Quote composition should separate plant from optics owned by IT.
Lock before price
Fibre count, connector family, enclosure and test method belong in the brief before mobilisation. See Fibre vs copper backbone.