1. The Optical Module Landscape
Since SFP was born in 2005, optical modules have evolved through SFP → SFP+ → SFP28 → QSFP+ → QSFP28 → QSFP-DD → OSFP → QSFP112. Here is the mainstream comparison:
| Form Factor | Data Rate | Physical Interface | Typical Application | Thermal Class |
|---|---|---|---|---|
| SFP+ | 10 Gbps | Duplex LC | 10G server access, 10G switch uplink | 1.5 W |
| SFP28 | 25 Gbps | Duplex LC | 25G server access, GPU cluster management | 2.5 W |
| QSFP+ | 4×10 = 40 Gbps | MPO-12 / Duplex LC | 40G aggregation, ToR uplink | 3.5 W |
| QSFP28 | 4×25 = 100 Gbps | MPO-12 / Duplex LC | 100G backbone, AI cluster interconnect | 4.5 W |
2. Select by Transmission Distance
Within the same form factor, laser wavelength and fiber medium determine distance coverage from desktop to metro.
2.1 Short Reach (0-100 m): DAC Copper First
- DAC (Direct Attach Cable) is passive copper with no optical module IC — just connectors, lowest cost;
- Typical specs: SFP+ DAC 3m/5m, QSFP28 DAC 3m/5m;
- Near-zero power draw, top choice for in-rack server-to-ToR connections.
2.2 Medium Reach (100 m - 500 m): Multimode + OM3/OM4/OM5 Fiber
| Fiber Grade | 10G SR | 25G SR | 100G SR4 |
|---|---|---|---|
| OM3 | 300 m | 70 m | 70 m |
| OM4 | 400 m | 100 m | 100 m |
| OM5 | 440 m | 150 m | 150 m |
Rule of thumb: higher data rates mean shorter multimode reach. For greenfield 25G/100G data centers, deploy OM5 straight away.
2.3 Long Reach (500 m - 40 km): Single-Mode + OS2 Fiber
- LR (Long Range): 1310 nm single-mode, 10 km — the workhorse for campus and inter-datacenter links;
- ER (Extended Range): 1550 nm single-mode, 40 km, metro backup;
- ZR / ZR+: Coherent, 80-120 km, submarine cables and DCI.
3. Select by Compatibility
Different vendors enforce optical module whitelists — plug in the wrong one and you get "Vendor Not Approved" or no recognition at all. Every EZMAX module is factory-tested against multiple vendors and can be pre-coded for:
- Cisco / Cisco Nexus
- Huawei / CloudEngine
- H3C S-series
- Ruijie RG-N18000
- Juniper QFX / EX
- Arista 7050 / 7280
- Mellanox / NVIDIA Spectrum
Tell us your target switch model when ordering — we pre-code and label them for free.
4. Common Mistakes
- Mistake 1: SFP+ and SFP28 look identical — can I mix? No. SFP28 has upgraded electrical specs; it is backward compatible with SFP+ ports, but SFP+ modules will not fit SFP28 ports;
- Mistake 2: Can QSFP+ break out to 4×10G? Yes — QSFP-4SFP+ breakout cables are a classic budget-saving technique;
- Mistake 3: Why does my 100G SR4 only reach 70 m? Because you have OM3; upgrade to OM4 to reach 100 m;
- Mistake 4: Can multimode go long distance? No — chromatic dispersion caps multimode at ~500 m; long reach demands single-mode.
5. EZMAX Quick Selection
| Scenario | Recommended Product | Fiber Type | Distance |
|---|---|---|---|
| In-rack interconnect | EZMAX SFP+ DAC 3m | Passive copper | < 5 m |
| 10G ToR uplink | EZMAX SFP+ 10G SR | OM3/OM4 | 300-400 m |
| 25G GPU cluster | EZMAX SFP28 25G SR | OM4/OM5 | 100-150 m |
| 40G aggregation | EZMAX QSFP+ 40G SR4 | MPO-12 OM4 | 150 m |
| 100G backbone | EZMAX QSFP28 100G SR4 | MPO-12 OM4 | 100 m |
| 10 km campus link | EZMAX SFP+ 10G LR | OS2 single-mode | 10 km |
| 100G long reach | EZMAX QSFP28 100G LR4 | OS2 single-mode | 10 km |
Conclusion: Optical module selection boils down to three dimensions — data rate → distance → compatibility — walk through them in order and you cannot go wrong. EZMAX offers a full portfolio from 10G to 100G, supports pre-coding for all mainstream switch brands, and works out-of-the-box with NETI710 10G NICs.