400G Active Optical Cable

The AOC-400G-QSFP-QDD is a 400G active optical cable designed to bridge QSFP112 host ports and QSFP-DD switch ports across OM3 or OM4 multimode fiber. Unlike passive DAC cables, active optics regenerate the signal at both ends, making them the preferred choice for any interconnect longer than a few meters in AI training clusters, hyperscale data-center fabrics, and high-performance computing (HPC) environments. Each end integrates four independent transmit and receive channels. On the QSFP112 side, a 4:4 DSP drives a 4-channel 850nm VCSEL array at 106.25Gbps per lane using PAM4 modulation, for an aggregate throughput of 425Gbps. On the QSFP-DD side, an 8:4 DSP adapts the four optical lanes to the eight 50G electrical lanes expected by the host connector — enabling plug-and-play interoperability without any host-side configuration. Maximum transmission distances are 30m on OM3 and 50m on OM4 fiber when the host enables Forward Error Correction (FEC) per IEEE 802.3db. The pre-FEC bit-error-rate floor is 2.4×10⁻⁴ (PRBS31Q at 53.125GBd), which falls well within the correction capability of standard KR4/KP4 FEC engines present in all modern 400G ASICs. Built-in digital diagnostic monitoring (DDM/DDMI) via CMIS 4.0 reports real-time temperature, supply voltage, per-lane optical power (TX and RX), and per-lane bias current over the TWI (I²C) interface — giving network operations teams full observability without external test equipment. Available cable lengths: 1m to 50m. All lengths ship as RoHS-compliant, lead-free assemblies rated for Class 1 laser safety.