Transceiver Reach Chart — Optic Names Decoded
Every suffix on an optic's label, decoded: what it means, how far it goes, and which glass it needs — with the basis column separating IEEE PMDs from MSA specs and pure vendor conventions. Reaches are the standardized values; a specific part can be rated differently, and the data sheet governs the warranty.
Suffix decoder
| Suffix | Meaning | Reach | Fiber | Basis |
|---|---|---|---|---|
| SX | 1G short wavelength, 850 nm | 275–550 m | Multimode | IEEE |
| LX | 1G long wavelength, 1310 nm | 5 km (550 m on MM + conditioning cord) | Single-mode | IEEE |
| SR | Short reach, 850 nm | 300 m OM3 / 400 m OM4 at 10G | Multimode | IEEE |
| LRM | Long reach multimode, 1310 nm | 220 m on legacy MM | Multimode | IEEE |
| LR | Long reach, 1310 nm | 10 km | Single-mode | IEEE |
| ER | Extended reach, 1550 nm | 40 km | Single-mode | IEEE |
| ZR | Beyond ER, 1550 nm | 80 km | Single-mode | vendor |
| SR4 / SR8 | SR × N parallel lanes over MPO | 100–150 m OM4 | Multimode (parallel) | IEEE |
| LR4 / ER4 | 4 wavelengths WDM-muxed on one duplex pair | 10 km / 40 km | Single-mode (duplex) | IEEE |
| DR / DR4 | Data-center reach, 100G/lane PAM4, parallel SM | 500 m | Single-mode (parallel MPO) | IEEE |
| FR / FR4 | 2 km duplex reach class | 2 km | Single-mode (duplex) | IEEE |
| BiDi | Single strand, two wavelengths, A/B paired | Per reach class | One strand | MSA |
| CWDM4 | 100G: 4 × 25G CWDM wavelengths, duplex LC | 2 km | Single-mode (duplex) | MSA |
| PSM4 | 100G: 4 × 25G parallel SM, 8 fibers, MPO | 500 m | Single-mode (parallel MPO) | MSA |
| SWDM4 | 40/100G over duplex multimode, 850–940 nm | 350–440 m (40G on OM4/OM5) | Multimode (duplex) | MSA |
Form factors
| Form factor | Max speed | Lanes |
|---|---|---|
| SFP | 1G | 1 |
| SFP+ | 10G | 1 |
| SFP28 | 25G | 1 |
| QSFP+ | 40G | 4 × 10G |
| QSFP28 | 100G | 4 × 25G |
| QSFP56 | 200G | 4 × 50G PAM4 |
| QSFP-DD | 400G (800G in -DD800) | 8 × 50G PAM4 |
| OSFP | 400G / 800G | 8 |
Reading an optic part number
The pattern is form factor + speed + suffix: “SFP-10G-SR” is a 10G short-reach multimode optic in an SFP+ cage; “QSFP-100G-LR4” is 100G over duplex single-mode to 10 km. The suffix decides the glass — SR-class needs the multimode grades on the distance chart, everything LR and beyond needs OS2 — and parallel suffixes (SR4, DR4, PSM4) additionally need MPO trunks with the right polarity. When a link budget is tight, the loss math lives on the loss budget page.
Common questions
What is the difference between SR and LR transceivers?
Wavelength and glass. SR (short reach) runs 850 nm on multimode — 300 m on OM3, 400 m on OM4 at 10G. LR (long reach) runs 1310 nm on single-mode to 10 km. They are not interchangeable: the optic must match the fiber type in the ground, which is why the fiber decision on day one constrains every optics purchase after it.
What do ER and ZR mean?
ER (extended reach) is the IEEE 40 km optic at 1550 nm. ZR — 80 km — was never IEEE; it is a de facto vendor convention that everyone honors. Both are strong enough to overload a receiver on short spans: plan a fixed attenuator (typically 5 dB) on ER links under 20 km.
What is the difference between 400G DR4, FR4, and LR8?
Reach classes on single-mode: DR4 runs 500 m over four parallel fibers (MPO); FR4 runs 2 km over one duplex pair using four CWDM wavelengths; LR8 is the IEEE 10 km optic (eight wavelengths). Note the trap: the IEEE 4-wavelength long optic is LR4-6 at 6 km — the "LR4-10" parts sold for 10 km exceed the spec and are vendor-engineered.
Are SFP and SFP+ interchangeable?
Mechanically yes, electrically no — the cage is the same but the host lanes differ. An SFP (1G) optic usually works in an SFP+ (10G) port at 1G if the switch supports it; the reverse never works. The same one-way story holds up the ladder (SFP28 ports usually accept SFP+). Form factors are all MSA-defined — IEEE specifies the signal, never the package — and vendor lock-in via coded EEPROMs is a purchasing fact to plan around.
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