Hi, I currently have these 400G QDD transceivers break out into 4x100G ports working fine:

QSFP-DD-400G-DR4, CISCO-INNOLIGHT, nominal bitrate is 425000 MBit/sec per channel, Link length SMF is 0.5 km, Nominal transmitter wavelength is 1311.00 nm, Advertising code is Optical Interfaces: SMF

then we wanted to go farther and got these a little cheaper Peak Fiber QDD that seems to be the same:

QSFP-DD-400G-DR4, Peak Fiber, nominal bitrate is 425000 MBit/sec per channel, Link length SMF is 0.5 km, Nominal transmitter wavelength is 1311.00 nm, Advertising code is Optical Interfaces: SMF

I have same QDD on both sides and just connected lane 1 but link never goes up, they seems to receive even though shows no tx.

try to configure FEC but doesnt support it, only FEC auto works. I am using an MPO SM fiber split into 4 pairs on both sides and just connecting the first path.…