Cooling 8×100GbE switch blades with high power optical modules

Eight high-power QSFP modules were modeled using Flotherm to determine the thermal requirements to keep the module case temperature below 70°C with 40°C air at 3 Km elevation. A detailed model for the QSFP, cage and air channel were used to determine the heat sink solution and airflow required to cool two - 1×4 QSFP cages, with each QSFP dissipating 5 Watts. Different heat sinks, baffles and airflow conditions were evaluated. Factors like contact resistance between the case and the heat sink, heat sink base heat spreading and effect of airflow bypass were investigated. The two factors that affected the module case temperature the most were the airflow through the heatsink and the contact resistance between the module and the heatsink.