Understanding Vertical Eye Closure Penalty (VECP)

This article explains the concept of VECP (Vertical Eye Closure Penalty), a crucial parameter in the optical domain. We’ll explore its definition, how it’s used, and the formula involved in its calculation.

What is VECP?

VECP, or Vertical Eye Closure Penalty, is a test parameter used in the calibration process. Specifically, it’s used to calibrate a reference TP3 signal for a Device Under Test (DUT). This is particularly important when measuring the DUT’s sensitivity to stress.

Think of it as a way to quantify how much “closed” or distorted an eye diagram becomes under stress.

The image above shows a stressed eye diagram, highlighting the parameters like A0 and OMA used in VECP measurement.

VECP Formula Explained

The VECP isn’t just a concept; it’s calculated using a specific formula:

Here’s a breakdown of what each part of the formula means:

• A0: This represents the amplitude of the eye opening. It’s measured from the 99.95th percentile of the lower histogram to the 0.05th percentile of the upper histogram. Essentially, it’s the height of the “open” part of the eye diagram.
• OMA: This stands for Optical Modulation Amplitude, which is another measure of the signal’s power.

In essence, the VECP formula is comparing the size of the eye opening (A0) relative to the Optical Modulation Amplitude (OMA). This helps determine how significantly the signal is impacted under stress conditions.

By analyzing VECP, engineers can understand the robustness and performance of optical communication systems.