Cable and Standard Reference
The distances that actually apply, copper categories, multimode and single mode fiber, and the connectors that go with them. All copper categories share a 100 m channel limit for standard speeds, so the category sets the achievable speed over that run, not the length.
COPPER CATEGORIES
| CATEGORY | SPEED AND DISTANCE | BANDWIDTH | NOTES |
|---|---|---|---|
| Cat5e | 1 Gbps to 100 m | 100 MHz | The legacy gigabit baseline, still widely deployed. |
| Cat6 | 1 Gbps to 100 m, 10 Gbps to 55 m | 250 MHz | 10 Gbps only on shorter runs, limited by alien crosstalk. |
| Cat6a | 10 Gbps to 100 m | 500 MHz | The recommended choice for new 10 Gbps cabling. |
| Cat7 | 10 Gbps to 100 m | 600 MHz | An ISO class F standard, not TIA, uses GG45 or TERA connectors. |
| Cat8 | 25 to 40 Gbps to 30 m | 2000 MHz | Short data center links only, fully shielded. |
MULTIMODE FIBER, SHORT REACH OPTICS
| FIBER | CORE | 10G-SR | 40G-SR4 | 100G-SR4 | COLOR |
|---|---|---|---|---|---|
| OM1 | 62.5 um | 33 m | not supported | not supported | orange |
| OM2 | 50 um | 82 m | not supported | not supported | orange |
| OM3 | 50 um | 300 m | 100 m | 70 m | aqua |
| OM4 | 50 um | 400 m | 150 m | 100 m | aqua or violet |
| OM5 | 50 um | 400 m | 150 m | 100 m | lime green |
SINGLE MODE FIBER, LONG REACH OPTICS
| STANDARD | FIBER | WAVELENGTH | REACH |
|---|---|---|---|
| 1000BASE-LX | OS1 or OS2 | 1310 nm | 5 km |
| 10GBASE-LR | OS2 | 1310 nm | 10 km |
| 10GBASE-ER | OS2 | 1550 nm | 40 km |
| 40GBASE-LR4 | OS2 | 1310 nm | 10 km |
| 100GBASE-LR4 | OS2 | 1310 nm | 10 km |
| 100GBASE-ER4 | OS2 | 1550 nm | 40 km |
DIRECT ATTACH, IN RACK AND ADJACENT RACKS
| TYPE | REACH | NOTES |
|---|---|---|
| DAC, passive | up to 3 m | Copper twinax with fixed transceivers, cheapest way to link ports in a rack. |
| DAC, active | up to 7 m | Powered copper for slightly longer in row runs. |
| AOC | up to 30 m, longer available | Active optical cable, fiber with fixed ends, for cross rack links beyond DAC reach. |
CONNECTORS
| CONNECTOR | USE |
|---|---|
| LC | Small duplex connector, the most common today for SFP and SFP+. |
| SC | Larger square push pull connector, common in older datacom links. |
| ST | Bayonet style, legacy multimode, still seen in older plants. |
| MPO or MTP | Multi fiber connector for parallel optics, used by 40G and 100G SR4. |
| FC | Screw on connector, legacy and test equipment. |
HOW TO CHOOSE
Copper or fiber
For a run inside a building under 100 m, copper is usually the right answer, cheaper and simpler, and the category sets the speed, Cat6a for new 10 Gbps work, Cat6 only if the run is short. Copper hits a hard 100 m limit for standard Ethernet regardless of speed. Past 100 m, or between buildings, or where you need to grow beyond 10 Gbps, move to fiber.
Multimode or single mode
Multimode is the short reach, lower cost choice for inside a building or a data center, its 850 nm optics are cheaper but its distance is limited, roughly 300 m on OM3 and 400 m on OM4 at 10 Gbps. Single mode is the long reach choice for between buildings and across a campus, its 1310 and 1550 nm optics reach kilometers. Do not use OM1 or OM2 for 10 Gbps, start at OM3.
Match the cable to the transceiver
The fiber determines the module, not the other way around. A single mode transceiver uses a 1310 nm laser for a 9 um core, a multimode transceiver uses an 850 nm VCSEL for a 50 um core, and the two do not interoperate. Never splice single mode to multimode, and if you must bridge fiber types use a media converter.
Measure the real length
Always plan on the actual routed length of the cable, not the straight line distance on a drawing. Ceiling height, cable tray paths, and drops to switches add up quickly, so a room that is 60 m across can be a 90 m run. Measure the real path and leave slack before comparing against the distance limits above.