What is a 400G FR4 QSFP-DD module? The 400G FR4 QSFP-DD module (Cisco model QDD-400G-FR4-S) is a high-performance fiber optic module that supports data transmission rates up to 400Gbps. It uses a QSFP-DD (Quad Small Form Factor Pluggable Double Density) interface and is suitable for network devices that require large bandwidth and high-speed connections. FR4…