TDECQ · Transmitter Dispersion Eye Closure Quaternary
The dB measure of how far a transmitter's eye is already closed before the channel; margin erodes as case temperature rises, so qualify optics at field temperature rather than on a cool bench.
Current numbers
0.5–1.5 dBTDECQ margin erosion from 25°C bench to ~65°C AI-rack case temp — why links pass at install and flap under load