Linear Drive Optics Test Demo

This detailed presentation by Paul Forrest provides valuable insights into the advancements and testing methodologies essential for the next generation of high-speed, low-power data transmission technologies, reinforcing Keysight Technologies' role in pioneering measurement solutions for the data center and AI-driven applications.

In the video, Paul Forrest, a solutions engineer with Keysight Technologies’ Network and Data Center group, presents an overview of physical layer test solutions for 112G linear drive optics (LDO, or LPO) or simply linear optics. Forrest begins by highlighting the increasing demand for higher speed data transmission and artificial intelligence applications, which necessitate data links with reduced power consumption and cost. He notes that LPO transceivers are emerging as a solution to meet these needs due to their significant advantages over conventional transceivers.

Forrest explains that LPO transceivers differ from conventional ones primarily by the removal of the DSP (Digital Signal Processing) functional block. This modification leads to lower power consumption, reduced by up to 50%, along with decreased cost and latency. The development and standardization of LPO requirements are governed by the OIF-CEI 112G linear standard, which is currently in progress. Keysight Technologies is actively involved in this standard development, contributing with cutting-edge measurement science to push the standard forward.

The demonstration begins with the G800GE layer one traffic generator, which generates an 8-lane 112G PAM-4 signal. This signal is driven into a linear transceiver housed within a test fixture. An optical loopback setup routes the signal back through the transceiver to the G800GE. To capture and analyze signal waveform measurements, Forrest utilizes several advanced instruments, including the N1060A precision waveform analyzer and the N1092A optical channel DCA-M.

Measurements are taken at various test points. At TP2, the optical output of the transceiver, measurements such as Optical Modulation Amplitude (OMA), extinction ratio, and TDECQ are performed. These measurements are facilitated by routing the signal through a breakout cable to the N1092 DCA-M. Another critical measurement point is TP4, the electrical output of the device. Here, new measurement parameters, such as Voltage Modulation Amplitude (VMA) and Electrical Eye Closure Quaternary (EECQ), are introduced. EECQ is noted as the electrical equivalent of the familiar optical TDECQ measurement. With the DSP function removed, placing greater responsibility on the host ASIC for equalization and drive level control.

Forrest emphasizes the importance of using new reference receivers and equalization functions when performing these measurements. The N1010A FlexDCA sampling oscilloscope software is showcased for its capability to easily create these functions. Specifically, for the TP4 measurement, the reference receiver consists of a two-stage CTLE (Continuous-Time Linear Equalizer) and a one-tap DFE (Decision Feedback Equalizer).

Forrest concludes the video by inviting viewers to learn more about the solutions presented by contacting their local Keysight representative or visiting www.keysight.com/find/800g.