What is eye diagram?

The eye diagram is a common indicator of the quality of the signal in high-speed digital transmission. The eye diagram usually includes some time samples of the voltage required for the data at a sample rate lower than the data rate. A perfect eye diagram contains a huge amount of parameter information about the signal, as it is derived from physics, regardless of the frequency of these effects.

The eye diagram provides instant visual data, which engineers can use to check the signal integrity of the design and find problems early in the design process. Used in combination with other measurements such as bit error rate, eye diagrams can help designers predict performance and identify possible sources of problems.

In the test, there is a close relationship between the eye diagram and the quality. If the eye diagram is good and stable, it means that the quality of the module is good.

There are many different eye shapes out there, and so are eye patterns. We can quickly judge the signal quality from the shape characteristics of the eye diagram.

1. The eye diagram in the figure below has "double eyelids", which can determine that the signal may have crosstalk or pre (de)emphasis.

2. The eye diagram in the figure below "eyes are covered with bloodshot eyes", which indicates that the signal quality is too poor. It may be caused by an error in the test method or an obvious error in the PCB wiring.

3. A complete eye diagram should include all state groups from "000" to "111", and eight states form an eye diagram.

The final effect is clearly visible in the eye diagram produced.

In order to make the optical module products work stably, we test the eye pattern through bare fiber (20km/40km/80km). All SFP, XFP, QSFP28, DWDM, CWDM, BIDI, 10G SFP+ XFP DWDM Tunable transceiver, copper etc optical module must pass the testing, then HTF can arrange the shipment.

Any questions? 

Contact Ivy from HTF team and will assist you asap.

Email: support@htfuture.com