QUESTION-LED PLANNER
Use this planner before you accept a substitute for a qsfp cable 100g requirement. The usual object is a QSFP28 assembly: four electrical lanes near 25.78125 Gb/s, NRZ, inside one shell. A breakout to four SFP28 ends is a different line from a straight QSFP28-to-QSFP28 lead.
01
Passive twinax at 100G is commonly a short inside-rack lead. Ask the supplier for the maximum meters on your host, and for AWG in the 30 AWG to 26 AWG range they actually build. Active copper and active optical cables add watts and a powered end. Insertion loss and return loss must come from that part datasheet, with the temperature of the measurement. Commercial notes often say 0 °C to 70 °C until replaced by the sheet.
02
A 100G SR4-style path is often multimode, around 850 nm, with an MPO connector and an optical budget you must request. A longer single-mode path is often discussed near 1310 nm, with dispersion and reach set by that design. Receiver sensitivity and transmit power belong on the module line. The ITU-T optical-fibre index, opened on 2026-10-27, is a question source for the fiber plant. It does not qualify a DAC. Do not let a supplier fold these into the copper price.
03
OEM-coded QSFP28 memory may align with a vendor support policy. A compatible code may widen sourcing if that host and software release accept it. A new lead may offer a clearer warranty path. A refurbished lead may cover a legacy cage when condition, provenance, and EEPROM are verified. Write the host model so both sides of each dispute answer the same platform. SFF-8636 is the management map buyers often ask QSFP28 suppliers to confirm. This desk did not re-test that map on 2026-10-27.
04
Compare per assembly or whole order in one currency. Pull coding, test sheets, freight, duties, and destination out of the headline. High-end, mid-range, budget, or undecided is your preference, not a factory score. An IEEE 802 overview read on 2026-10-27 can suggest the 100G clause to ask the supplier to map. It is not interoperability evidence for an untested pair.
A QSFP28 shell is not a QSFP-DD shell and not an OSFP shell. Reject a 200G or 400G substitute that changes the cage unless the faceplate actually has that cage. Count breakout legs. Four SFP28 ends are not one far-end QSFP28 plug.
A longer AOC is not a longer passive DAC. Ask watts, wavelength, fiber mode, connector, and optical budget on the glass offer. Impedance near 100 ohm differential is a copper question. Frequency range and connector mating cycles come from the named datasheet. FEC requirements stay with the host manual.
Demand the manufacturer, model, and a current datasheet. A family photo, a matching latch color, or a brochure rate is not the test table. Compliance talk has to name the model. LinkScope Sourcing 03 does not stock the lead, does not measure decibels, and does not approve the link.
Worked situation: a buyer needs thirty straight 100G leads, 1 m and 2 m mixed, for one leaf model, dock in the United States, week stated in the form. The desk asks two plants for passive copper and one plant for an AOC alternative with wavelength and watts. The result is three packets with deviations marked, not a selected winner and not a measured saving. Cable options remain inquiry labels.
Copy the five checklist lines into the form, plus any cell you are deliberately leaving open. The desk coordinates factory questions. It does not close optical budget math or host qualification for you. Contact handling describes the reply path.
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