400G QSFP-DD transceivers are addressing the technical challenges of achieving high speed 400G interconnections. The transceivers have four optical lanes that operate at 100Gbps PAM4 modulation, providing solutions up to 400 Gbps. The transceivers have on the electrical side 8 lanes of 53.125Gbps PAM4. They are compliant with the QSFP-DD MSA (DD = Double Density). Digital diagnostics functions are available via the I2C interface, as specified by CMIS (Common Management Interface Specification).