USource 400GBASE-DR4 QSFP-DD transceiver module is suitable for 0.5 km optical communication applications. It converts 8 channels of 50Gb/s (PAM4) electrical input data to 4 channels of parallel optical signals, each capable of 100Gb/s operation for an aggregate data rate of 400Gb/s. On the receiver side, the module converts 4 channels of parallel optical signals of 100Gb/s each channel for an aggregate data rate of 400Gb/s into 8 channels of 50Gb/s (PAM4) electrical output data. Host FEC is required to support 0.5 km fiber transmission.