Power classes & typical consumption by module type

A switch cage delivers a fixed budget of 3.3 V power and removes a fixed amount of heat. A module declares the class it needs, the host compares it with what the cage can do, and the mismatch shows up as a module stuck in low power or a port that overheats. This page is the lookup for both sides: the class ladders per form factor with the bytes that carry them, and the wattage real modules actually draw — for cage limits, PSU sizing and cooling calculations.

Class ladders by form factor

Low-power mode is ≤ 1.5 W for every family that has one; the host releases it only after validating the class (Power & thermal, Host initialization).

Typical consumption of real modules

Values are typical maximums from datasheets of common products; class is the declared ceiling, consumption the measured draw.

Roughly: VCSEL SR < DFB LR < EML/TEC ER-ZR < PAM4 DSP < coherent, and the DSP accounts for half or more of a 400G+ module's power (Module electronics).

Supply, current and inrush

Heat and cooling

Symptoms of overrun and what the host does: Power & thermal.

Choosing by power

1. Read the cage limit from the platform's hardware guide (per port, sometimes per group).
2. Compare with the module's declared class (bytes above) — not with the datasheet typical.
3. For 10GBASE-T SFP+, ZR/tunable SFP+, 400G ZR and 800G modules, confirm explicitly.
4. Sum optics power for PSU sizing on high-radix boxes; add it to the ASIC and fan budget.
5. Prefer LPO or lower-class PMDs where the link allows — power is also cooling and cost.

In CodingBox

The declared power class and maximum power bytes are shown on the Check screen for SFF-8472, SFF-8636 and CMIS modules; editing them does not change what the module draws, only what the host believes — a coded class lower than the real draw trips port protection instead of a polite low-power hold (Check transceiver, EEPROM editor).