The ATOP 400G QSFP-DD FR4 CWDM 2km Transceiver is a high-quality 400G FR4 module designed for 2km optical communication applications and is compliant with the 100G Lambda MSA standard. This QSFP-DD module can convert 8-channel 53.125 GB/s electrical data to 4-channel 106.25 GB/s optical signals and multiplex them into a single channel for 425 GB/s optical transmission. Similarly, it optically demultiplexes a 425 GB/s input into 4-channel signals and converts them to 8-channel output electrical data on the receiver side, accessible via a two-wire serial interface.