SFP, SFP+, QSFP and QSFP+ Explained: Transceivers for Network+
A transceiver is the removable module that converts between a switch's electrical signalling and the optical or copper medium outside it. Modular transceivers let one switch port support fibre or copper at various distances by changing a small plug-in module. The form factors Form factor Speed Lanes SFP 1 Gbps 1 SFP+ 10 Gbps 1 SFP28 25 Gbps 1 QSFP+ 40 Gbps 4 × 10 QSFP28 100 Gbps 4 × 25 QSFP-DD 400 Gbps 8 × 50 The Q in QSFP stands for quad — four lanes in parallel. That single fact explains the whole family: QSFP+ is four SFP+ lanes at 10 Gbps giving 40, and QSFP28 is four SFP28 lanes at 25 giving 100. It also explains breakout cables : because a QSFP+ port is four independent lanes, it can be split into four separate 10 Gbps connections. That is a genuinely useful trick for connecting four servers to one switch port, and a likely exam point. The older GBIC is the predecessor to SFP — larger, 1 Gbps, essentially obsolete but still named on exams. SFP is sometimes cal...