A New DSP-Free Optical Test Bar Targets AI Rack Power

OIF, the Optical Internetworking Forum standards body, published CEI-112G-LINEAR-PAM4 in August 2026, and the spec gives the industry its first repeatable way to test whether an optical module can talk to a host ASIC without a heavy digital signal processor in the signal path. Synopsys says its 112G PHY IP is the first to clear that bar, with up to 50% claimed module power savings.

Today, optical links between AI compute racks run the signal through a power-hungry DSP in the module to clean up distortion. Linear-drive optics skip that retranslation step. Without an interoperability spec, "linear" was a vendor talking point; with one, "linear" is a multi-vendor test.

The first-claim announcement comes from a Synopsys-sponsored whitepaper excerpt on Semiconductor Engineering. It names measured TX/RX results "meeting and in several cases exceeding" CEI limits, though the full characterization data (TX VMA, jitter, eye-closure, RX JTOL) sits behind the gated PDF and is not in the public excerpt.

What remains untested: whether "exceeds spec" holds up under multi-vendor interoperability testing, and whether hyperscalers' optics teams will treat a single-vendor first claim as a procurement signal. The spec now gives them a way to find out.