With the rapid development of high-definition display technology, the HDMI 2.1 standard has emerged, bringing higher bandwidth and more functional support. In particular, the advantages of Active Optical Cables (AOC)in transmitting high-bandwidth signals have made them stand out in long-distance transmission. This article will delve into the testing process of HDMI 2.1 AOC and its significance.
Generally, manufacturers of HDMI optical engines measure the transmitter (Tx)and receiver(Rx)optical engines separately, which is somewhat different from the testing of finished HDMI AOC products. However, the essence remains the same. Since AOCs use fiber optics for transmission, traditional S-parameter measurements are not suitable for AOCs. In most cases, HDMI AOC manufacturers use 8K TVs to test signals with AOCs. This test usually relies on the human eye to detect several conditions such as black screens, flickering screens, resolution issues, and flashing dots. This method is highly subjective and is greatly related to the sensitivity of the human eye. Moreover, it is almost impossible to detect a few flashing dots. Additionally, many customers in the industry use bit error rate testers for related tests, which mainly target the high-speed part and are relatively coarse, with a longer measurement duration.
To address these issues, we adopt a scientific production testing method to replicate the phenomena. We use our company's CCBT-12A HDMI transmission line testing system to identify the root causes. The CCBT-12A HDMI transmission line testing system developed by Te-lead Technologies has the following features for measuring HDMI AOCs:
Independent power consumption monitoring at both ends of the AOC
Low-speed signal continuity monitoring
High-speed channel crosstalk monitoring
Eye diagram measurement for different HDMI standards,resolutions,and equalization settings
Scatter bit error statistics
We have created a simple table to summarize how to quantify the quality of HDMI optical engines and AOCs through data.Failures are not only caused by high-speed issues but often also by low-speed and power supply problems,which can become testing blind spots.
Display Issue | CCBT-12A Testing Method |
Black screen | Low-speed continuity, power consumption monitoring, eye diagram template measurement |
Resolution | Eye diagram measurement based on resolution and HDMI version |
Flickering | Eye diagram template measurement, scatter bit error statistics |
Flashing dots | Scatter bit error statistics |
To further analyze signal stability, different presets and equalization can be used for failure analysis to understand potential issues on various display devices. The eye height, eye width, random jitter (Rj),deterministic jitter(Dj),and rise/fall times of the eye diagram can be used for more detailed high-speed signal analysis, which can help identify potential problems in the electro-optical or opto-electrical conversion process.
Additionally, the production line requires quick measurements. Users can select the required test items based on their testing needs for production.
Of course, the measurement methods of the CCBT-12A are diverse. Different HDMI optical engines or AOC failures may have different manifestations. There are many real-world measurement cases, and more testing methods can be discussed with the technical engineers of Te-lead Technologies.
For more information on testing solutions for USB4,TBT, DP,etc.,including LDR, AEC, and AOC transmission cables, please contact Shenzhen Te-lead Technologies Co.,Ltd.directly at, sales@te-lead.com