DIRECT ANSWER / 01
Confirm equipment and mating parts before freezing cable configuration
A 400G breakout is not merely a split of “total fibre count.” It is determined by the transceiver, host-port mode and target rate. Cisco’s official material shows that selected 400G DR4 / VR4 modules support specific 100G or 200G breakouts; that does not make every 400G module freely breakable.
Freeze the source and target modules first, then use the vendor-supported lane relationship to define MPO ports, branch interfaces, polarity and lengths. A breakout link should be drawn per port and per lane.
SELECTION MATRIX / 02
Purchasing decision matrix
| Item | Identify | Correct action | Avoid |
|---|---|---|---|
| Source | Full 400G module reference and host-port mode | Determines vendor-supported breakout combinations | Writing only “400G to 4×100G” |
| Optical interface | MPO-12, MPO-16 or LC | Determines mechanical interface and usable lanes | Guessing the interface from total fibre count |
| Target | 100G / 200G target module references | Confirms remote interface, end face and architecture | Confirming only the source end |
| Mapping | Position of every branch and lane | Makes TX/RX and labels verifiable | Using a single A/B/C label instead of a complete map |
RFQ INPUTS / 03
Minimum inputs a supplier can verify
| Category | Required input or confirmation |
|---|---|
| Source | Full module reference, port configuration and vendor-supported breakout target |
| Remote end | Equipment and module reference for every target port |
| Cable | Main interface, branch interface, APC/UPC, gender, polarity and length datum |
| Acceptance | Port labels, fibre-by-fibre continuity, project test method and report requirements |
BUYER FAQ / 04
Purchasing FAQ
Does every 400G optic support 4×100G?
No. Breakout capability is defined by official support for the module and platform.
Does an MPO-12 end always break out to four LC ends?
No. Branch interfaces depend on module architecture and the target modules; do not infer them from connector appearance alone.
Can an installed MPO trunk be reused?
Review fibre type, end face, count, polarity, loss budget and complete map.
What does a supplier need?
Module references at both ends, port mode, breakout drawing, length datum, quantity and acceptance requirements.
SOURCES / 05
Sources and applicability
Sources checked: 2026-09-22. This guide clarifies purchasing fields; it does not replace current equipment data sheets, full standards or the approved project drawing.