TDECQ stands for Transmitter and Dispersion Eye Closure Quaternary. It is a standardized measurement — defined under the IEEE 802. If pattern lock is selected, ensure that Acquire. Standards bodies like IEEE have defined measurement metrics to quantify the performance of an optical transceiver and ensure inter-operability. Optical modulation amplitude (OMA) indicates the strength of the modulation power. For legacy NRZ systems, eye-mask tests place polygons below, within, and above the NRZ eye diagram and verify where the. In data center optics, 4-level Pulse Amplitude Modulation (PAM4) signaling is gradually overtaking Non-Return to Zero (NRZ) signaling. [1-3] Although both signaling schemes use intensity modulation and direct detection, PAM4 encodes two bits into four intensity levels, reducing bandwidth. Optical PAM-4 modulation is becoming increasingly pervasive for short-range links up to several kilometers, as evidenced by the decision of the IEEE 802. 3bs Task Force to adopt it for its emerging 400 GbE standard. The move from NRZ signaling to higher-order formats offers increased capacity at the.