A 400G DR4 transceiver is an optical module that supports 400Gbps Ethernet or IB transmission over parallel single-mode fiber. It uses 4 parallel lanes of 100G PAM4 signaling, transmitted and received via an MPO-12/APC connector. SR (Short Range): Up to 300 meters, using multimode fiber for. 400G QSFP-DD optical transceivers come in various flavors: SR8, DR4, FR4, LR4, and more. QSFP-DD DR4 has a key advantage in that it can interoperate with 100G single lambda optics.