Optical interface MSAs: CWDM4, PSM4, 100G Lambda, ZR/ZR+

Three kinds of document define a pluggable module. Form-factor MSAs (SFP, QSFP-DD, OSFP) fix the mechanics and electrical pins; management specifications (SFF-8472, SFF-8636, CMIS) fix the memory map; and the optical interface — wavelengths, powers, reach, coding — comes either from a formal standard (IEEE 802.3 for Ethernet, T11 for Fibre Channel, IBTA for InfiniBand, ITU-T for transport) or from an interface MSA: a group of vendors agreeing on a PMD the standards bodies had not (yet) written. Many of the most common data-centre optics are MSA interfaces, and their names are on the label, in SFF-8024 codes and in CMIS applications.

Why interface MSAs exist

IEEE standardises a small set of reaches per rate (for 100G: SR4, LR4, ER4 and later DR, FR1, LR1). Operators wanted cheaper 2 km and 500 m options, duplex multimode, bidirectional fibre, and coherent DWDM in a pluggable — so vendors wrote MSAs in months rather than the years an IEEE project takes. Several were later adopted or superseded by IEEE clauses, but the MSA names stuck.

The catalogue

MSA / group	Founded	Defines	Medium & reach	Codes
10x10 MSA	2011	100G as 10 × 10G wavelengths (CFP)	SMF 2 / 10 / 40 km	legacy
100G PSM4	2014	4 × 25G parallel single-mode, 1310 nm, MPO	SMF 500 m	Table 4-4 07h
100G CWDM4	2014	4 × 25G on 1271–1331 nm CWDM, duplex LC	SMF 2 km	06h
CLR4 Alliance	2014	CWDM4 variant intended to run without FEC	SMF 2 km	17h
SWDM Alliance	2015	40G/100G SWDM4: 4 wavelengths 850–940 nm on duplex MMF	OM4/OM5 100–150 m	1Fh / 20h
4WDM MSA	2017	100G 4WDM-10 / -20 / -40 on LAN-WDM wavelengths	SMF 10 / 20 / 40 km	22h–24h
100G Lambda MSA	2017	100G per wavelength PAM4: 100G-FR, 100G-LR, 400G-FR4, 400G-LR4-10, later 100G-ER1-30/40	SMF 2 / 10 / 30–40 km	26h, 27h, 48h, 49h
400G BiDi MSA	2018	400G-BD4.2 — 8 × 50G on 4 duplex MMF pairs, two wavelengths per fibre	MMF 70–150 m	became IEEE 400GBASE-SR4.2
OIF 400ZR	IA 2020	400G coherent DWDM (16QAM, CFEC) in QSFP-DD/OSFP, amplified metro	SMF 80–120 km amplified	4Ah (400GBASE-ZR in IEEE)
OpenZR+ MSA	2020	extends 400ZR: oFEC, 100–400G multi-rate, longer reach, QPSK/8QAM/16QAM	SMF regional	CMIS applications
OpenROADM MSA	2016	operator-driven coherent 100–400G plus open line-system YANG models	SMF long haul	CMIS applications
800G Pluggable MSA	2019	800G-FR4 (4 × 200G, 2 km) and 800G-PSM8 / DR8 (8 × 100G, 500 m)	SMF	800G media IDs
OpenEye MSA	2019	analog (DSP-free) PAM4 optics for 50G–400G to cut power and latency	SMF / MMF	vendor-specific
COBO	2015	on-board optics form factor and management (uses CMIS)	—	identifiers 02h-class
CFP MSA	2009	CFP / CFP2 / CFP4 / CFP8 form factors for 40G–400G, incl. coherent CFP2-DCO/ACO	—	form factor
25G / 50G Ethernet Consortia	2014 / 2016	single-lane 25G and 50G Ethernet ahead of IEEE 802.3by / 802.3cd	—	adopted by IEEE
QSFP-DD, OSFP, SFP-DD, DSFP MSAs	2016–2018	form factors and (with OIF) CMIS/MIS management	—	Form factors

Years are the founding or first-release year of each group; exact dates and revisions are on the MSA sites.

MSA vs IEEE: interoperability traps

Pairing	Interoperable?	Why
100G CWDM4 ↔ 100G CLR4	usually	same wavelengths; CLR4 specifies FEC-free operation — host FEC settings must match
100G CWDM4 ↔ 4WDM-10	no	4WDM uses LAN-WDM wavelengths (1295–1310 nm), not CWDM
100G PSM4 ↔ 100GBASE-DR4 / 400G DR4 breakout	no	PSM4 is 4 × 25G NRZ; DR is 100G PAM4 per fibre
100G-FR / 100G-LR (Lambda MSA) ↔ 100GBASE-FR1 / LR1 (IEEE)	yes	IEEE adopted the MSA parameters
400G-FR4 (MSA) ↔ 400GBASE-FR4 (IEEE)	yes	same
400ZR ↔ OpenZR+	only in 400ZR mode	ZR+ modules usually support the 400ZR application too
40G SWDM4 ↔ 40GBASE-SR4	no	duplex MMF with 4 wavelengths vs parallel MPO

Always read the module's compliance code rather than the marketing name: Compliance codes, Physical mismatches.

Where these optics appear

Data-centre leaf/spine — PSM4 and CWDM4 dominated 100G; 400G-FR4/DR4 and 800G-DR8 follow the same pattern (Ethernet optical interfaces).
Campus and enterprise MMF — SWDM4 and BiDi to reuse duplex OM3/OM4 for 40G/100G.
Metro and DCI — 400ZR/ZR+ replace transponders with pluggables (Coherent & long haul).
AI clusters — 800G DR8/2×FR4 per the 800G MSA and IEEE 802.3df (Optics in AI fabrics).

In CodingBox

CodingBox names MSA interfaces from their SFF-8024 codes and CMIS application IDs on Check transceiver — 100G CWDM4, 400G-FR4, 400ZR — so a module's real interface is visible regardless of what the label says.