SFP

The Small Form-factor Pluggable (SFP) replaced the GBIC and became the most common optical module ever made. Its footprint is still used, unchanged, by SFP+, SFP28 and SFP56 — which is why a modern 50G port is physically the same size as a 1G port from two decades ago.

Key facts


Lanes × rate	1 × up to ~4.25 Gb/s
Total	1G class (also 2G/4G FC, OC-3/12/48)
Connector	LC duplex (also simplex BiDi, RJ45 copper)
Supply	3.3 V
Applications	1000BASE-SX/LX/EX/ZX/BX, 1/2/4GFC, SONET/SDH, CWDM/DWDM SFP

Specifications

INF-8074 — SFP Transceiver 1.0: the original SFP MSA (mechanical, electrical).
SFF-8432 — SFP+ Module and Cage: the improved mechanical definition also used

for SFP.

SFF-8472 — Management Interface: identification, DDM and thresholds.
SFF-8079 — SFP Rate and Application Selection; SFF-8089 — *SFP Rate and

Application Codes*.

SFF-8075 — PCI Card Version of SFP Cage.

Management interface

SFP uses the two-address model of SFF-8472:

A0h — serial ID: vendor, part number, serial, transceiver codes, wavelength,

distances, and the CC_BASE / CC_EXT checksums.

A2h — digital diagnostics: live monitors, alarm/warning thresholds, flags, and

— on protected modules — the password area at offset 0x7B.

Not every 1G SFP implements A2h diagnostics; a capability bit in A0h says whether DDM is present.

Compatibility notes

Fits SFP+, SFP28 and SFP56 cages (rate permitting).
Coloured CWDM SFPs and DWDM SFPs use the same memory layout with the

wavelength field set — see CWDM.

In CodingBox

Fully supported: read, decode, edit and write per SFF-8472 with automatic CC_BASE/CC_EXT recalculation in the EEPROM editor. Protected modules are handled through Protected memory & passwords.