An SFP port (Small Form-factor Pluggable) is a modular slot on a network switch or router that accepts a hot-swappable transceiver module. Rather than building network equipment with fixed optical or copper interfaces, manufacturers provide SFP slots that let the buyer choose the specific transceiver type for each port. The same switch can use fibre on some ports and copper on others, simply by inserting the right SFP module.

In short: Common SFP variants include SFP (up to 1 Gbps), SFP+ (up to 10 Gbps), SFP28 (up to 25 Gbps), and QSFP (multi-lane modules at 40 Gbps, 100 Gbps, or higher). Transceivers are available for multimode fibre over short distances, single-mode fibre over long distances, copper Ethernet (1000BASE-T SFP), and specialist applications like coarse or dense wavelength division multiplexing for telecoms. Most SFP modules are interoperable across vendors, although some vendors restrict their equipment to recognise only their own branded modules.

For IoT and industrial deployments, SFP ports are most commonly seen on the WAN side of larger industrial switches and on telecoms equipment. A site connected to fibre will typically present that fibre into a switch via an SFP module. SFP support in industrial switches like Teltonika's TSW models extends the switch's usefulness in deployments that mix copper and fibre, where the fibre might back-haul to a distant cabinet or aggregate multiple sites onto a single ring.

Selecting the right SFP module depends on the fibre type (single-mode or multimode), the distance (short reach, long reach, extended reach), the wavelength, and the data rate. Specifying the wrong module is one of the more common mistakes in fibre installations, so it is worth confirming compatibility with both the switch documentation and the upstream optical infrastructure before purchase.