QSFP28 (100 Gbps)
Direct Answer
QSFP28 (Quad Small Form-Factor Pluggable 28) is a 100 Gbps transceiver standard defined by SFF-8665 and IEEE 802.3bm. Integrating four 25 Gbps electrical lanes within the exact QSFP mechanical dimensions, it is the primary high-density interconnect for 100 Gigabit Ethernet and EDR InfiniBand.
Source: SFF Committee SFF-8665 / IEEE 802.3bm / CWDM4 MSA
Specs
| Standard / MSA | SFF-8665 / SFF-8636 / IEEE 802.3bm |
| Form Factor | QSFP28 |
| Electrical Channels | 4 lanes @ 25.78125 Gbps NRZ |
| Max Data Rate (Ethernet) | 103.125 Gbps |
| Max Data Rate (InfiniBand) | 100 Gbps (EDR) |
| Optical Connectors | MPO/MTP-12 (SR4, PSM4) or Duplex LC (CWDM4, LR4) |
| 4x25G Breakout Mode | Supported (to 4x SFP28 ports) |
| Typical Power Consumption | 3.5–5.0 W |
100G Form Factor Consolidation
Before QSFP28, 100G Ethernet required large CFP, CFP2, or CFP4 modules with 10x10G internal lanes. QSFP28 revolutionized datacenter switching by packing four 25G channels into the compact QSFP shell, enabling standard 32-port 100GbE 1RU switches delivering 3.2 Tbps aggregate switching capacity per rack unit.
Major 100G Standards
- 100GBASE-SR4: Multi-mode parallel optics (MPO-12) up to 100m.
- 100G-CWDM4: 4 uncooled wavelengths over duplex single-mode LC up to 2km (widely used by hyperscalers).
- 100GBASE-LR4: 4 LAN-WDM wavelengths over duplex LC single-mode fiber up to 10km.