OS2, OM3 and OM4 fibre: choosing the right fibre optic cable
Singlemode or multimode? A guide to OS2, OM3 and OM4 fibre, supported distances at 10, 40 and 100 Gb/s, connector types and which cable construction to use inside and outside.
Short answer: use OS2 singlemode for any link between buildings or over 300 m, and for anything you want to be future-proof. Use OM4 multimode for links inside a building where the optics are cheaper and the distance is under 400 m at 10 Gb/s. OM3 is still fine for short in-building links but there is little price difference, so buy OM4. OM1 and OM2 are legacy and should only be bought to match existing installations.
Distance by fibre type
| OM3 | OM4 | OS2 | |
|---|---|---|---|
| Core / cladding | 50/125 µm | 50/125 µm | 9/125 µm |
| 1 Gb/s | 1000 m | 1100 m | 5 km+ |
| 10 Gb/s | 300 m | 400 m | 10 km |
| 40 / 100 Gb/s | 100 m | 150 m | 10 km |
| Jacket colour | Aqua | Aqua or violet | Yellow |
Cable construction
- Tight buffered for internal and riser runs. Easy to terminate directly and flexible. See tight buffered fibre cable.
- Loose tube for external ducts. Gel or dry water-blocked tubes; needs a transition to pigtails or a breakout kit. See loose tube fibre cable.
- Steel wire or steel tape armoured for direct burial, rodent protection and crushing risk. See SWA fibre cable.
How many cores?
Every duplex link uses two cores. A 4-core cable gives you two links, an 8-core gives four. Fibre is cheap compared with the installation, so a 12 or 24-core backbone between buildings is normal even where only two links are needed today.
Connectors and presentation
LC is the modern default for switches and SFP modules; SC is common on older kit and in FTTx; ST is legacy. Terminate at a 19 inch fibre patch panel or wall box by fusion splicing pigtails onto the cable, then connect to equipment with patchcords. Match the fibre type of the pigtail and patchcord to the cable exactly.
Testing
Every fibre link should be inspected and cleaned before connection, then tested with an optical loss test set (Tier 1). Long or spliced links should also have an OTDR trace (Tier 2). Our Fibre Testers range covers both.
Unsure? Send us the run lengths, the switch optics you plan to use and the route (internal, duct or buried) and we will specify the cable, cores and connectivity.