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What is TDECQ | Transmitter dispersion and eye closure

This page describes TDECQ (Transmitter dispersion and eye closure) definition used in optical domain. It also mentions TDECQ (Transmitter dispersion and eye closure) formula or equation.

Definition:
• New TDECQ metric is employed in optical domain in order to characterize quality of transmitted/received signal instead of traditional eye mask analysis.
• It is a measure of each optical transmitter's vertical eye closure when transmitted through a worst case optical channel.


stressed eye diagram and its parameters

The figure depicts eye diagram of optical stressed signals for PAM4 and NRZ optical receivers.

TDECQ (Transmitter dispersion and eye closure) Formula or Equation

Following is the formula or equation of TDECQ (Transmitter dispersion and eye closure).


TDECQ,Transmitter dispersion and eye closure

Where,
OMA stands for Optical Modulation Amplitude, measured in µW.
➤ER stands for Extinction Ratio, measured in dB or %.
➤UI stands for Unit interval i.e. one bit period
➤A0 stands for Vertical Eye Opening i.e. inner-most eye opening at the center of the eye; measured in dBm or µW.
➤VECP stands for Vertical Eye Closure Penalty, measured in dB.
➤SEC stands for Stressed Eye Closure, measured in dB.
➤TDECQ stands for Transmitter and Dispersion Eye Closure.

TDECQ conformance test

TDECQ conformance test block diagram

The conformance test block diagram for TDECQ measurement is shown in the figure-2 above. As shown test pattern is transmitted repetitively by optical lane under test and the oscilloscope is used to capture complete pattern for TDECQ test and analysis.



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