SFP112

SFP112 brings the single-lane SFP to 100 Gb/s by running its one electrical lane at 100G PAM4 — the same lane rate as QSFP112, in the familiar SFP outline. It is the first SFP that is managed through CMIS rather than SFF-8472, so to a host it looks less like an SFP28 and more like a one-lane QSFP112.

Key facts

Specifications

• SFP-DD MSA hardware specification — the SFP-DD MSA defines SFP112 alongside SFP-DD and the two-lane SFP-DD112: mechanical outline (SFP compatible), the 112 Gb/s-per-lane connector and cage, thermal requirements.
• Electrical: 100GAUI-1 (IEEE 802.3ck) — one 100G PAM4 lane.
• Management: CMIS — see CMIS; identifier 20h from SFF-8024.

Management interface

The largest change from SFP56 is invisible from the outside: SFP112 leaves the two-address SFF-8472 layout (A0h/A2h) for CMIS, the model of QSFP-DD, OSFP and QSFP112, reduced to one lane. Byte 0 reports identifier 20h; the module exposes CMIS lower memory (module state, flags, controls) and paged upper memory for identity, application advertisement and diagnostics, and the host brings it up through the CMIS state machine — low power → high power → data path activation — after selecting an application. A host or tool that assumes SFF-8472 in an SFP cage misreads an SFP112, so both have to check the identifier first. The two-lane SFP-DD uses its own CMIS-derived MIS; SFP112 skips MIS and uses CMIS directly.

Compatibility notes

• An SFP112 port typically accepts SFP56, SFP28 and SFP+ modules at their rates, provided the host supports those rates and their SFF-8472 management.
• An SFP112 module needs 100G-per-lane SerDes and CMIS support in the host; in an SFP56 or SFP28 port it will not link.
• SFP112 is the single-lane sibling of QSFP112 (4×100G) and the usual far end of a 4×100G breakout from a 400G DR4 port.
• 100G single-lane optics rely on RS-FEC (544,514) on the host side; a FEC mismatch between the two ends is a common reason for no link.

In CodingBox

CodingBox recognises SFP112 modules by the identifier 20h and reads them with the CMIS decoder — module state, identity, applications and diagnostics appear in the EEPROM editor and on the DDM screen, as for QSFP112. For CMIS-specific bring-up problems see CMIS issues.