QSFP+ (40 Gbps)
Direct Answer
Quad Small Form-Factor Pluggable Plus (QSFP+) is a 40 Gbps transceiver standard defined by SFF-8436. Integrating four 10 Gbps electrical channels into a compact form factor, it supports 40 Gigabit Ethernet (40GbE), InfiniBand QDR/FDR, and 4x10G breakout configurations using MPO/MTP-12 or duplex LC connectors.
Source: SFF Committee SFF-8436 / IEEE 802.3ba (40GBASE-R)
Specs
| Standard / MSA | SFF-8436 / IEEE 802.3ba |
| Form Factor | QSFP+ (Quad SFP+) |
| Electrical Channels | 4 lanes @ 10.3125 Gbps NRZ |
| Max Data Rate (Ethernet) | 41.25 Gbps |
| Max Data Rate (InfiniBand) | 56 Gbps (FDR) |
| Optical Connectors | MPO/MTP-12 (SR4) or Duplex LC (LR4 / BiDi) |
| 4x10G Breakout Mode | Supported (1x MPO to 4x duplex LC) |
| Typical Power Consumption | 1.5–3.5 W |
Parallel Optics vs Wavelength Multiplexing
QSFP+ achieves 40 Gbps through two primary optical techniques:
- Parallel Optics (40GBASE-SR4): Uses an MPO/MTP-12 fiber connector where 4 fibers transmit and 4 fibers receive simultaneously over OM3/OM4 multi-mode fiber up to 100m/150m.
- Coarse Wavelength Division Multiplexing (CWDM / 40GBASE-LR4): Multiplexes 4 distinct optical wavelengths (1271, 1291, 1311, 1331 nm) onto a single duplex LC single-mode fiber pair up to 10km.
Breakout Capabilities
A key operational feature of QSFP+ 40GBASE-SR4 is 4x10G channelization. A single 40G QSFP+ switch port can be configured to breakout into four independent 10G SFP+ server connections using an MPO-to-4xLC breakout fanout cable or copper DAC breakout.