TDECQ Part 1: Making Accurate and Repeatable Compliance Measurements
TDECQ is the acronym used to describe “transmitter dispersion and eye closure quaternary”. This is a power penalty metric that describes how much extra power is required from a transmitter, relative to an ideal transmitter, to compensate for both non-ideal transmitter waveforms and the impact of chromatic dispersion. It is similar to the transmitter dispersion penalty (TDP) metric used in NRZ optical communications standards. It was developed in the IEEE 802.3bs standard and improved in the IEEE 802.3cd standard. It is a convenient way to specify the performance of a PAM4 transmitter, as it aggregates many transmitter attributes into a single metric, and the metric directly indicates the impact a transmitter’s imperfections will have on overall system-level performance.