D4 86100A Oscilloscope Eye Diagram Understanding

1. Brief Introduction

High-speed digital signals are composed of high-level-low-level-high-level switching. When the speed is very fast, the signal will be distorted, resulting in errors in the transmitted data.

In order to describe this error, we introduce an oscilloscope eye diagram to visualize it. We are connecting an optical signal here to see the degree of distortion of the optical signal switch.

2. Understanding

The eye diagram is actually a multiple recording of high and low level lines, with high and low levels switching in the middle. Normally, we need a square wave, but in the case of high speed, shorten the time axis and it becomes a diagonal line.

A good signal should have a high overlap, and the lines of the eye diagram will be relatively small. The hexagon in the middle is the set parameter. If the points of the eye diagram fall within the hexagon, it means that the eye diagram is not good.

3 Parameter understanding

1 Ext.ratio means extinction ratio, which is the ratio of high level to low level. The extinction ratio is generally 11-14dB

2 Avg power is the optical power entering the eye diagram

3 Crossing is the eye diagram crossing point, 50% is better, 40-60 is also acceptable.

4 Margin Eye diagram margin is generally 15, good 20, poor 10

5 Wfms total points, smpls red points, failed points.