The 400G QSFP-DR4 optical module uses a 1310nm EML transmitter type, with signals modulated via PAM4 (Pulse Amplitude Modulation). It can transmit over single-mode fiber for distances up to 500 meters, suitable for short-distance 400G, 200G, and 100G optical interconnects. 400G VR4 modules are ideal for intra-data center connections where high-bandwidth, short-range links are necessary. Among the most widely deployed options, 400G FR4 and 400G DR4 are two standards frequently used in modern cloud and hyperscale environments. Although both deliver a total transmission rate of 400Gbps, they differ significantly in fiber architecture, transmission distance, connector type, and. One such type is 400G DR4. The product is designed with digital.