PAM4 is Here!

By John D'Ambrosia

We are at a unique point in Ethernet’s history. During the development of IEEE Std 802.3bs™-2017 for 200 GbE and 400 GbE, a critical decision was made to shift from 25 Gb/s NRZ signaling to 50 Gb/s PAM4 signaling, both electrically and optically. And this decision is spilling over into new Ethernet specifications for 50GbE and 100 GbE, as well as new physical layer solutions for 200 GbE and 400 GbE that were not part of the 802.3bs standard.

These documents are the foundation of the Next Ethernet Era , as company after company is leveraging 50 Gb/s PAM4 signaling technology for their next generation Ethernet products targeting 50 GbE through 400 GbE. As with every other new technology that Ethernet has introduced, there is a momentary pause where the industry at large wonders, “will this new technology continue Ethernet’s tradition and support multi-vendor interoperability.

It is at these exact moments the Ethernet Alliance and its members step up. Through our multi-vendor interoperability demonstrations at shows like OFC and ECOC and our private member plugfests, we lead the industry in making the investment to test and confirm the multi-vendor interoperability that is expected of them. That is why I am happy to share that our latest plugfest , which tested 10 different Ethernet solutions, ranging from 25GbE to 400GbE, including both 25 Gb/s NRZ and 50 Gb/s PAM4 signaling, yielded very promising results, with 98 percent of link configuration tests and 93 percent of Frame Error Rate (FER) tests passing. As Chairman of the Ethernet Alliance, I congratulate the members of the Ethernet Alliance who participated in this plugfest and thank all of the engineers for their hard work.

Our work is not done, however, as our next plugfest to perform additional 25GbE to 400GbE interoperability testing, which will further prove out these technologies, such as PAM4 electrical and optical signaling. For those companies who are not members of the Ethernet Alliance participating in our plugfests, I strongly encourage you to consider joining. It goes without saying the larger the number of participants, the louder our collective voice will be in saying to the industry that these Ethernet solutions are ready for deployment.