PAM-4 analysis software on Keysight oscilloscopes

December 17, 2015 // By Graham Prophet
Keysight Technologies has issued software that provides automated PAM-4 pre-compliance testing and report generation; it automates testing of the PAM-4 measurements outlined in IEEE 400G Ethernet (P802.3bs) and OIF-CEI-56G-PAM4, operating on real-time and equivalent-time (sampling) oscilloscopes.

Designed to quickly and accurately measure and quantify PAM-4 (pulse amplitude modulation with four amplitude levels) signals, the software is used with the Keysight S-Series, 90000A, V-Series, 90000 X- and Z-Series real-time oscilloscope platforms and the 86100D DCA-X Infiniium sampling oscilloscope. N8836A PAM-4 analysis software (for S-Series, 90000A, V-Series, 90000 X- and Z-Series oscilloscopes) and N1085A PAM-4 analysis software (for 86100D oscilloscopes) provide comprehensive characterisation of electrical PAM-4 signals based on the Optical Internetworking Forum’s Common Electrical Interface (OIF-CEI 4.0) proposed 56G interfaces, and the emerging IEEE 400 Gigabit Ethernet (P802.3bs) standard.

Conventional communication techniques have often relied upon NRZ (non-return-to-zero) encoding, but excessive channel losses and crosstalk on 56 Gb/sec NRZ links make this technology impractical for many applications. One way to overcome this challenge is to change the modulation technique from NRZ to pulse amplitude modulation. However (Keysight observes) there is not yet consensus within the governing bodies of communication standards as to how to measure PAM-4 signals for compliance. “Our customers face new design and measurement challenges as they work to ensure their products are compliant with specifications that are incorporating PAM-4 signaling,” said Dave Cipriani, vice president and general manager of Keysight’s Oscilloscope and Protocol Division. “We’re working with industry leaders and standards organisations in these very early stages to help customers address these challenges and get to market quicker.”

The N8836A and N1085A PAM-4 measurement applications for S-Series, 90000A, V-Series, 90000 X- and Z-Series real-time oscilloscopes and 86100D DCA-X Series sampling oscilloscopes deliver measurements such as:

Linearity and output voltage measurements including level separation mismatch ratio (RLM)

Eye width (EW) and eye height (EH)

Jitter measurements including even-odd jitter and clock random jitter

Differential and common mode return losses – performed using a Keysight time domain reflectometer (TDR) or vector network analyzer (VNA)

Multi-level signalling systems are particularly susceptible to noise, so Keysight’s V-Series, Z-Series and S-Series offer the industry’s lowest noise floors for wide-bandwidth,