Core Points - The article discusses the differences between QSFP and QSFP-DD modules, highlighting the complexity of newer optical modules and network technologies, especially from the 400G generation onwards [2] - The primary distinction between the two types of optical modules lies in their electrical connection capabilities, with QSFP-DD featuring more connection pads for enhanced connectivity [3][5] - QSFP28 supports 4 channels at 28G (actual rate 25G), achieving a total transmission of 100Gbps, while QSFP56 increases the single-channel rate to 56G (actual rate 50G), allowing for 200Gbps transmission [5] - QSFP-DD utilizes a second row of pads to enable 8 channels, facilitating 400Gbps transmission with configurations such as QSFP56-DD (8x50G) and QSFP28-DD (8x25G) [6] - The QSFP-DD connector is longer but maintains a similar external cage size to QSFP, allowing QSFP modules to be used in QSFP-DD cages [8] - There is backward compatibility with QSFP-DD, allowing QSFP devices to function in QSFP-DD cages, but not vice versa due to the increased number of electrical connections in QSFP-DD [9] - Understanding optical modules can be simplified into three core components: packaging form, electrical connection configuration, and optical connection configuration, with a focus on packaging and electrical connections for high-speed networks [10]