Power Consumption Comparison of 400G QSFP-DD Optical Modules

Standard 400G QSFP-DD modules typically consume 10–14 watts, while high-power and coherent variants can exceed 20 watts, with silicon photonics-based modules achieving as low as 7 watts.

Standard QSFP-DD Modules

Typical 400G QSFP-DD modules consume between 10 and 14 watts under normal operating conditions. The variation depends on factors such as laser count, DSP complexity, and optical amplification requirements. First-generation discrete-laser designs were less efficient, whereas modern silicon photonics-based FR4 modules reduce power consumption to around 7 watts, lowering thermal output and cooling requirements .

High-Power QSFP-DD Modules

High-power or "Bright" QSFP-DD modules, such as Cisco's 400G QSFP-DD High-Power variant, are designed for enhanced optical transmission and include miniaturized optical amplifiers. These modules maintain a compact form factor but consume more power than standard modules due to additional Tx power and integrated amplification, typically exceeding standard 10–14 watt ranges .

Coherent and Long-Haul Modules

Coherent QSFP-DD modules for metro and long-haul applications consume significantly more power because of sophisticated DSPs and tunable lasers. A fully populated 32-port switch with ZR+ coherent modules can dissipate over 700 watts of optical power, highlighting the need for careful thermal management .

Comparison with Other 400G Form Factors

• OSFP modules: Designed for higher power and thermal dissipation, supporting smooth evolution to 800G/1.6T. They generally consume slightly more power than QSFP-DD due to larger form factor and higher performance capabilities .
• QSFP112 modules: Offer a balance between bandwidth, power consumption, and port density, often slightly more energy-efficient than OSFP but comparable to QSFP-DD in typical Ethernet deployments .

Summary Table

Understanding these differences is critical for data center power budgeting, thermal design, and operational cost planning, especially when scaling to hundreds or thousands of 400G ports .