Optical fiber carries signals as light, immune to the electrical noise and distance limits of copper. In AV it shows up in three places: long HDMI/HDBaseT runs (active optical or fiber extenders), AV-over-IP uplinks and backbones, and inter-building links. Choosing fiber comes down to multimode vs single-mode, then the specific grade.
Multimode vs single-mode
- Multimode (MMF) — larger core (50 or 62.5 µm) lets light travel multiple paths (“modes”). Cheaper optics, shorter reach. Uses 850/1300 nm sources (often VCSELs). Aqua, violet, or lime jackets by grade.
- Single-mode (SMF) — tiny 9 µm core carries one path, so almost no modal dispersion. Longer, higher-bandwidth reach; pricier optics. Uses 1310/1550 nm lasers. Yellow jacket.
Grades at a glance
| Type | Core (µm) | Color | 10G reach | 40/100G reach |
|---|---|---|---|---|
| OM1 | 62.5 | Orange | ~33 m | not supported |
| OM2 | 50 | Orange | ~82 m | not supported |
| OM3 | 50 | Aqua | ~300 m | ~100 m |
| OM4 | 50 | Aqua/violet | ~400 m | ~150 m |
| OM5 | 50 | Lime | ~400 m | ~150 m (+ SWDM) |
| OS1/OS2 | 9 | Yellow | 10 km+ | 10 km+ |
Reach figures are typical maximums and depend on the transceiver optics. Always match the fiber grade to the transceiver’s rated distance for the target speed.
Connectors you’ll meet
- LC — small form factor, the dominant connector on modern SFP/SFP+ optics and AV-over-IP gear.
- SC — larger square push-pull, common on legacy and some extender equipment.
- ST — bayonet, older installs.
- MPO/MTP — multi-fiber ribbon connector for 40/100G and high-density trunks.
Where each fits in AV
- Room-to-rack HDMI/HDBaseT — active optical HDMI or fiber extenders, usually OM3/OM4.
- AV-over-IP leaf/spine uplinks — OM3/OM4 within a building; OS2 between buildings or on long campus runs.
- Anything over ~300–400 m or inter-building — single-mode (OS2); multimode won’t reach.
Practical notes
- Don’t exceed the bend radius. Tight kinks cause loss and can crack the glass.
- Keep it clean. Contaminated end-faces are the #1 cause of fiber faults — inspect and clean before mating; cap unused connectors.
- OM5 vs OM4. OM5 mainly adds short-wavelength division multiplexing (SWDM) headroom; for typical AV distances OM4 is usually sufficient.
Related
- Ethernet Cabling · HDBaseT
- Sizing an AV-over-IP backbone? See AV-over-IP Network Design.
Sources
- ISO/IEC 11801 — generic cabling standard defining the OM (multimode) and OS (single-mode) fiber classifications.
- ANSI/TIA-568.3 & TIA-492 — optical fiber cabling components and OM/OS designations adopted by TIA.
- IEC 60793-2-10 — multimode fiber categories and modal-bandwidth specifications.