PAM4 · Pulse Amplitude Modulation, 4-level
Four-level signaling that carries two bits per symbol to double lane rate, at the cost of a much smaller eye that makes forward error correction and transmitter margin mandatory.
Current numbers
100-200 Gb/sPAM4 SerDes per-lane rate driving 800G/1.6T links — FEC-mandatory, BER-screening-critical