In short: 10G SR runs over multimode fiber for short links (up to about 300 m), LR over single-mode fiber up to 10 km, ER up to 40 km and ZR up to 80 km. For very short links inside a rack, a direct attach cable is usually the better choice, and for a normal network cable there is the 10G copper module.
SFP+ is the most common 10G module in switches, servers and storage systems. This guide shows which type fits which link.
The 10G SFP+ types side by side
| Type | Fiber / cable | Wavelength | Typical reach | Typical use |
|---|---|---|---|---|
| SR | multimode | 850 nm | up to 300 m | inside a data center or building |
| LR | single-mode | 1310 nm | 10 km | between buildings, campus |
| ER | single-mode | 1550 nm | 40 km | between sites in a region |
| ZR | single-mode | 1550 nm | 80 km | long links between cities |
| T | copper (RJ45) | – | 30 m | devices with a 10G network port |
| DAC | fixed copper cable | – | 0.5–10 m | inside a rack |
SR – the standard for short links
SR modules use multimode fiber and an 850 nm laser. They are the most economical optical choice for links inside a data center or a building. The reach depends on the quality of the fiber: modern OM3 and OM4 multimode fiber supports the full distance, older fiber less. If your links stay within one building, SR is usually the answer.
LR – 10 km over single-mode fiber
LR modules use single-mode fiber and a 1310 nm laser for up to 10 km. They connect buildings, floors of a campus or a company to its provider. Because single-mode fiber is not limited by distance inside a site, many networks use LR even for shorter runs to keep one module type everywhere.
ER and ZR – long distances
When the distance grows beyond 10 km, ER modules reach about 40 km and ZR modules about 80 km, both at 1550 nm over single-mode fiber. They are used between sites and by service providers. Their lasers are strong: on a very short fiber they can overload the receiver on the other side, so pick the module that matches the actual distance.
10G copper and direct attach cables
Not every 10G link needs fiber:
- The 10GBASE-T module has an RJ45 socket and works over a good network cable for up to about 30 m. It is the bridge to devices with 10G copper ports. Read 10G copper SFP+: is it a good option?
- A direct attach cable (DAC) is a copper cable with an SFP+ module fixed on each end. For connections inside a rack it is the cheapest and simplest option. For longer runs there are active optical cables – see DAC vs AOC vs transceivers.
10G direct attach cables from 0.5 to 10 mPassive and active DAC – coded for your switch on both ends.
BiDi, CWDM and DWDM
For special cases there are more types: 10G BiDi modules use a single fiber for both directions, and CWDM and DWDM modules work on a specific wavelength so that many links can share one fiber pair. See BiDi transceivers explained and CWDM vs DWDM.
How to choose
- Inside the rack? A DAC cable.
- Inside a building on multimode fiber? SR.
- Single-mode fiber? LR up to 10 km, ER up to 40 km, ZR up to 80 km.
- The same type on both ends, coded for the equipment it goes into – see our SFP compatibility guide.
Frequently asked questions
What is the difference between 10GBASE-SR and 10GBASE-LR?
SR uses multimode fiber and covers short distances (up to about 300 m); LR uses single-mode fiber and reaches 10 km.
Can I connect an SR module to an LR module?
No. They use different fiber types and wavelengths. Both ends of a link need the same type.
Can a 10G SFP+ module run at 1G?
Most 10G optical modules run at 10G only. If one side of the link is 1G, use 1G SFP modules on both ends – most SFP+ ports accept them.
