Transceiver (pluggable optics)
termStands for: Pluggable transceiver form factors (GBIC to SFP, QSFP, OSFP)
The pluggable module that gives a switch port its personality - copper or fiber, short reach or long, one lineage from GBIC to OSFP.
Instead of fixing the optics at manufacture, ports take standardized pluggables: the chunky GBIC gave way to the SFP, then SFP+ (10G), SFP28 (25G), the quad-lane QSFP+ / QSFP28 (40/100G), and QSFP-DD and OSFP at 400G and beyond. The module choice - SR, LR, DAC twinax, RJ45 copper - decides medium and distance; the form factor decides what fits the port. Vendor lock-in games on 'unsupported' third-party optics are a running industry argument.
The transceiver is where a port's physical layer actually lives. A switch built with empty cages leaves the medium and the reach to the module: short-reach multimode at 850 nm, long-reach single-mode at 1310, copper over twisted pair, or a direct-attach cable. The IEEE's names say which: in 10GBASE-SR, BASE is baseband, S short wavelength and R the scrambled 64B/66B coding; in 100GBASE-SR4, the final 4 counts lanes on parallel fibre.
Reach belongs to the pair, module and fibre, never to the module alone. The same 10GBASE-SR module that covers 400 m of OM4 covers 33 m of OM1, and an LR module is specified for single-mode fibre, not multimode. That is why a transceiver swap is the first suspect after a cabling change, and the module's own diagnostics, its transmitted and received power, are the first numbers to read.
Also known as: transceiver, gbic, sfp+, qsfp, qsfp-dd, osfp, pluggable optics