PAM4 (Pulse Amplitude Modulation 4) enables a PAM4 waveform to transmit twice as many bits as an NRZ waveform at the same symbol rate.
The 200G QSFP-DD AOC employs eight lanes that operate up to 25Gbps NRZ modulation each to provide bandwidth up to 200Gbps. However, the 200G QSFP56 AOC have only four-lane electrical interfaces, so it is required to use PAM4 modulation up to 50Gbps per lane so as to provide bandwidth up to 200 Gbps.
The different of 200G QSFP56 AOC and 200G QSFP-DD AOC will be introduced as follow.
The 200G AOCs are suitable for short distances and offer a cost-effective solution to connect within racks and across adjacent racks.
Gigalight offers a full range of 200G AOCs in both QSFP-DD and QSFP56 form-factors. The Gigalight 200G AOC product line includes 200G QSFP-DD AOC，200G QSFP-DD to 2x 100G QSFP28 AOC，200G QSFP-DD to 4x 50G QSFP28 AOC，200G QSFP56 AOC，200G QSFP56 to 2x 100G QSFP56 AOC，200G QSFP56 to 4x 50G SFP56 AOC. All of these cable assemblies are compliant to IEEE standards and industry Multi-Source Agreements (MSAs).
This is an original article wrote by Lafite. If reproduced, please indicate the source: https://www.gigalight.com/community/200g-qsfp56-aoc-and-200g-qsfp-dd-aoc/