400g qsfp cable

How to read a 400G reply before ranking the number

A 400G QSFP-family cable is usually discussed as a QSFP-DD shell with eight electrical lanes, often described around 50G PAM4 per lane, or as a later cage the host manual names. Write the cage from the switch faceplate. An OSFP shell is a different mechanical purchase even when the headline rate is also 400G. Keep it on a separate line if a supplier offers it as an alternative.

Ask for length in meters, AWG when the lead is copper, and whether the part is passive twinax, active copper, or an active optical cable. Passive copper loss climbs quickly at this lane rate, so a 0.5 m, 1 m, or 2 m figure is a specification, not a suggestion from this desk. Request the maximum length the supplier will support on the named host.

Management memory for QSFP-DD parts is often discussed under CMIS. Older QSFP28 parts are often discussed under SFF-8636. Ask which map the exact part uses, and whether the host software release reads it. Coding that works in one leaf switch can be rejected by another software train. That is a host question, not a catalog badge.

If the path leaves copper, record wavelength, fiber mode, connector, and optical budget. An 850 nm multimode alternative and a 1310 nm single-mode alternative are different plants. Dispersion and reach belong to that glass line. Insertion loss and return loss should be copied from the supplier table at the temperature they state, commonly discussed as 0 °C to 70 °C for commercial gear until the datasheet says otherwise.

Normalize money after scope matches: per assembly versus whole order, currency, Incoterm, freight, duties, coding fees, and test-sheet fees. A lower printed rate on a shorter lead, or on a copper part when you specified glass, is a different purchase. Quote preparation lists fields to align, and the RFQ form is where the brief is sent. FEC, power in watts, and connector mating cycles stay on the supplier datasheet for the named part number.