800G OSFP to 2x400G OSFP-RHS Passive Direct Attach Cable

This 800G to 2×400G direct attach cable breaks a single OSFP host port out into two independent OSFP-RHS links, letting one 800G switch port feed two 400G-capable devices without adding transceivers on either end. Inside the assembly, the 16 differential pairs on the OSFP connector are split and re-terminated across the two OSFP-RHS ends, with each of the eight lanes on every link carrying 50 or 100Gb/s of PAM4-modulated signal — the same electrical scheme defined in IEEE P802.3ck D3.0.

Each connector end carries its own EEPROM, so the host and both downstream devices can identify and configure the link independently over the I2C management interface; product information can be read back or reprogrammed as needed. Because signal timing and insertion loss on copper twinax degrade with distance, the cable is built and validated at three lengths — 0.5m and 1m in 30AWG, and 2m in 26AWG, the heavier gauge compensating for the added run length. All three variants are rated across a 0°C to 70°C case operating temperature range (storage: -20°C to 85°C), with humidity tolerance up to 85% RH under normal operating conditions.

The OSFP end uses the CTHS (Close Top Heat Sink, finned-top) housing to match standard 800G switch cages, while the two breakout ends use the lower-profile OSFP-RHS (Riding Heat Sink, flat-top) housing sized for adjacent-port density on NICs and HBAs. As a passive, transceiver-free alternative to fiber, this construction is intended for short-reach interconnects in data center racks, HPC clusters, and storage fabrics — including InfiniBand EDR/HDR/NDR deployments alongside standard 800GbE.