Glossary
Technology evolves at a rapid-fire pace. That’s why we’ve built an easy-to-use glossary to help you better understand the terms, technologies and trends that impact your business.PAM4
What is PAM4?
PAM4, or pulse amplitude modulation with four levels, is a signaling method that encodes two bits of data in each symbol using four distinct signal levels. This allows PAM4 to transmit twice as much data per symbol as NRZ signaling, which uses two levels.
PAM4 is widely used in high-speed Ethernet interfaces, including 400G, 800G and 1.6T, to increase data rates without requiring a proportional increase in symbol rate.
Why is PAM4 important?
Higher data rates make signal integrity more challenging. Because PAM4 uses four closely spaced signal levels, it provides less noise margin than NRZ and requires more advanced equalization, FEC and performance analysis.
Testing PAM4 signals helps engineers evaluate BER, signal quality and other impairments that can affect the performance of high-speed components, transceivers and interfaces.
Learn more
- Blog: New era of transceivers: 400G and beyond
- Videos: Leading-edge BER testing up to 800G
- EXFO glossary : 1.6T Ethernet