Eye diagram testing and adjustment is an important stage to ensure that the optical module obtains the best signal. Fundamentally, an eye diagram is a graphical representation of a digital signal's quality, formed. These eye mask definitions specify transmitter output performance in terms of normalized amplitude and time in such a way to ensure far-end receivers can consistently tell the difference between one and zero levels in the presence of timing noise and jitter. The measurement instrument that verifies. PLTS constructs measurement-based eye diagrams (or patterns) by convolving the calculated time domain impulse response (generated from frequency domain measurement data) with a synthesized pattern of bit sequences. The following is a simplified block diagram of the eye diagram creation process.