Agilent / Keysight N4891A 400GBASE FEC-aware Receiver Test Solution

The Keysight N4891A 400GBASE FEC-aware Receiver Test Solution is a physical layer bit error rate tester engineered for characterization and compliance validation of 400 Gigabit Ethernet receivers. Purpose-built to evaluate receiver performance under Forward Error Correction (FEC) conditions - a mandatory requirement for 400GbE system reliability - this instrument measures critical performance indicators including frame loss ratio and system margin under realistic stressed conditions. It delivers actionable insights into component and system design trade-offs driven by FEC requirements.

Technical Specifications

• Data Rate: 400GbE interfaces at 26.5625 GBaud PAM4


• FEC Support: RS-544 (KP4) FEC mode with symbol-striped physical layer BER testing


• Frame Loss Measurement: Quantifies FLR in 400G Ethernet links employing FEC


• Standards Compliance: IEEE 802.3 clauses 121, 122, 124, 136, 137, 138 (802.3bs and 802.3cd); 400GAUI-8 and 400GBASE-LR8/-FR8/-SR8 interface specifications

Key Features

• FEC-aware physical layer BER measurement with symbol striping


• FEC margin and compliance testing aligned with IEEE and OIF recommendations


• Layer 1 channel stress and impairment testing with optical receiver stress testing (ORST) capability


• Adjustable jitter injection, eye diagram analysis, and error characterization


• Layer 1 BERT 400GE test software with browser-based user interface


• KiOS operating system integration for streamlined test automation

Typical Applications

• Silicon communication device receiver characterization


• 400GbE compliance validation under FEC-stressed conditions


• System margin prediction in production and design environments


• Layer 1 physical layer stress testing and channel impairment analysis

Compatibility & Integration The N4891A integrates with the Keysight M8040A High Performance BERT (64 GBaud) to generate correct striped FEC test patterns on single lanes under test. Combines with the A400GE-QDD 400GE layer 1 BERT and KP4 FEC multiport test system to deliver aligned striped FEC traffic across remaining lanes. Compatible with Keysight FlexDCA Oscilloscopes via the M809256PB OIF CEI-56G Rx Test Automation Application for extended measurement capability.