In short: SX is for short multimode fiber links, LX for single-mode links up to 10 km, EX for 40 km and ZX for 80 km. T is the copper version with an RJ45 socket, and BX modules send and receive over a single fiber. Pick the type by the fiber you have and the distance you need to cover.
1G SFP modules are still the backbone of access networks, offices, campuses and industrial sites. Here is what each type is for.
The 1G SFP types side by side
| Type | Fiber / cable | Wavelength | Typical reach | Typical use |
|---|---|---|---|---|
| SX | multimode | 850 nm | up to 550 m | inside a building or a data center |
| LX | single-mode | 1310 nm | 10 km | between buildings, campus links |
| EX | single-mode | 1310 nm | 40 km | between sites in a city |
| ZX | single-mode | 1550 nm | 80 km | long links between cities |
| T | copper (RJ45) | – | 100 m | devices with a normal network port |
| BX | single fiber | two, one per direction | 10–80 km | where fiber is scarce |
The distances are the typical ones for each type; the exact value is always on the product page.
SX – short links over multimode fiber
SX modules use multimode fiber and an 850 nm laser. They are the most economical choice for links inside a building: between a floor switch and the core, or between racks. If the fiber in your walls is orange or aqua, it is most likely multimode. Our guide to single-mode vs multimode explains how to tell.
LX – the 10 km all-rounder
LX modules use single-mode fiber (usually yellow) and a 1310 nm laser, and cover up to 10 km. They are the default choice for links between buildings and across a campus, and they are among the most widely used SFPs.
EX and ZX – long distances
When a link has to cover more than 10 km, EX modules reach about 40 km and ZX modules about 80 km over single-mode fiber. They are used between sites, for example by service providers or between two locations of a company. Long-reach modules have stronger lasers, so on a very short fiber they can overload the receiver on the other side; for short links, choose the type that matches the distance.
T – copper with an RJ45 socket
The 1000BASE-T module turns an SFP port into a normal RJ45 network port for up to 100 m of standard network cable. It is useful when a device with only copper ports – a camera, a server, an access point – has to connect to an SFP port.
1G copper SFP (RJ45)Turns an SFP port into a normal network port, up to 100 m.
BX – one fiber instead of two
Standard modules need two fibers: one to send and one to receive. BiDi (BX) modules do both over a single fiber by using two different wavelengths. They always come in pairs – a "U" and a "D" version – and are useful where fibers are scarce or expensive to rent. More in BiDi transceivers explained.
How to choose
- Which fiber do you have? Multimode points to SX, single-mode to LX, EX, ZX or BX, a network cable to T.
- How long is the link? Pick the type whose reach covers the distance, with a little reserve.
- The same type on both ends (or a matching U/D pair for BiDi).
- Coded for your equipment, so the switch accepts it – see the SFP compatibility guide.
Frequently asked questions
What is the difference between 1000BASE-SX and 1000BASE-LX?
SX uses multimode fiber for short links up to a few hundred meters; LX uses single-mode fiber and reaches about 10 km.
Can an LX module work over multimode fiber?
It is not what LX is made for. Use SX modules on multimode fiber and LX on single-mode fiber.
Can I connect an SX module to an LX module?
No. Both ends of a link need the same type, because they use different wavelengths and different fiber.
