USource 400GBASE-FR4 QSFP-DD transceiver module is suitable for 2 km optical communication applications over single mode fiber. It converts 8 channels of 50Gb/s (PAM4) electrical input data to 4 channels of CWDM optical signals and multiplexes them into a single channel for 400Gb/s optical transmission. On the receiver side, the transceiver optically de-multiplexes a 400Gb/s optical input into 4 channels of CWDM optical signals and converts them to 8 channels of 50Gb/s (PAM4) electrical output data. Host FEC is required to support 2 km fiber transmission.