What is the difference between LX, LR, ER, and ZR optical modules?
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These reach-class abbreviations indicate distance capability, laser wavelength, and target fiber type.
1 Gigabit Ethernet Variants
- 1000BASE-SX: 850nm MMF, 220-550m
- 1000BASE-LX: 1310nm SMF, 10km (or MMF 550m)
- 1000BASE-EX: 1310nm SMF, 40km
- 1000BASE-ZX: 1550nm SMF, 80km (non-standard but common)
10 Gigabit Ethernet Variants
- 10GBASE-SR: 850nm MMF, 300m (OM3) / 400m (OM4)
- 10GBASE-LR: 1310nm SMF, 10km
- 10GBASE-LRM: 1300nm MMF, 220m (legacy MMF)
- 10GBASE-ER: 1550nm SMF, 40km
- 10GBASE-ZR: 1550nm SMF, 80km
25/100 Gigabit Variants
- 25GBASE-SR: MMF, 70-100m
- 25GBASE-LR: SMF, 10km
- 100GBASE-SR4: Parallel MMF, 100m
- 100GBASE-LR4: WDM SMF, 10km
- 100GBASE-ER4: WDM SMF, 40km
Understanding the Codes
- First letter: Wavelength (S=short 850nm, L=long 1310nm, E=extra long 1550nm)
- Second letter: Reach class (R=reach, X=legacy)
- Number suffix: Number of parallel channels (SR4 = 4x lanes)
Choosing the Right Module
| Distance | 1G | 10G | 25G |
|---|---|---|---|
| <300m MMF | SX | SR | SR |
| <10km SMF | LX | LR | LR |
| <40km SMF | EX | ER | ER |
| <80km SMF | ZX | ZR | ZR |
Common Mistakes
- Using LR on very short link → too much power, may overdrive receiver
- Using SR on multi-building link → distance too far
- Mixing wavelengths (1310nm to 1550nm) — won't work
2 Other Answers
17
Great summary. Add: for very short SMF links (<1km), consider attenuators to avoid overdriving receivers.
21
Match modules on both ends! Don't mix ER with LR or you get link issues.
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