Verifying 800 G DAC Performance with the VIAVI OneAdvisor 800
At 800 G, even minor connector wear or cable skew can cause bit-error bursts. This case study details how a global data-centre operator used the VIAVI OneAdvisor 800 to move high-speed cable qualification from the lab to the field.
Background
A global data-centre operator was upgrading its switching fabric to 800 G Ethernet, using a mix of QSFP-DD and OSFP direct-attach copper (DAC) interconnects to link top-of-rack switches and aggregation platforms.
While DACs provide a low-cost, low-latency option compared to optical transceivers, their signal integrity margins shrink dramatically at 112 G PAM4 lane speeds. Even minor issues—such as connector wear, crosstalk, or cable skew—can cause bit-error bursts or link instability.
Before installing thousands of cables across multiple sites, the operator’s engineering team needed a fast, repeatable way to verify each 800 G DAC met IEEE and MSA specifications for electrical performance.
The Challenge: Complexity at 800 G
At 800 G, DAC testing is no longer trivial. The team had to confirm:
- Lane integrity for eight lanes of 100 G PAM4 per connector.
- Return loss, insertion loss, and eye-diagram compliance.
- Bit-error-rate (BER) performance at target pre-FEC and post-FEC thresholds.
- CMIS (Common Management Interface Specification) compliance for EEPROM programming and vendor identification.
Traditional oscilloscopes and BERT systems in the lab could deliver these measurements but were slow, complex, and not portable, limiting their use for incoming-inspection or field validation. The engineers wanted a single compact test instrument that combined traffic generation, BER analysis, and cable diagnostics.
The Solution: VIAVI OneAdvisor 800
The team adopted the VIAVI OneAdvisor 800 (ONA-800) as their primary DAC validation tool. Designed for emerging high-speed Ethernet and pluggable technologies, the ONA-800 provided:
- Native QSFP-DD and OSFP interfaces, eliminating the need for adapters.
- Built-in BERT capability to generate full-rate 800 G traffic patterns across all lanes.
- PRBS (Pseudo-Random Bit Sequence) testing for stress verification.
- Real-time eye-diagram and signal-to-noise margin analysis to visualise lane quality.
- Automatic CMIS interrogation to verify cable EEPROM data, length, and manufacturer coding.
Each DAC under test was connected between two ONA-800 ports. The instrument ran a complete test sequence—BER, signal margin, skew, and eye mask—automatically logging results to VIAVI StrataSync® for traceability.
The Results
Testing hundreds of DACs revealed measurable variation across suppliers and production batches. The ONA-800 enabled engineers to:
- Identify cables with marginal BER performance before deployment.
- Detect incorrect or incomplete CMIS programming, preventing interoperability issues.
- Verify all eight lanes met IEEE 802.3ck electrical requirements for 112 G PAM4 signalling.
- Produce time-stamped compliance certificates for each cable, stored centrally for audit and warranty support.
By validating every 800 G DAC prior to installation, the operator prevented costly downtime and troubleshooting once racks were live.
Conclusion
The VIAVI OneAdvisor 800 delivered a practical, portable, and standards-based method to verify 800 G DAC cables quickly and confidently.
Combining bit-error testing, eye-diagram analysis, and CMIS verification in one platform allowed engineers to move high-speed cable qualification from the lab to the field—cutting testing time, eliminating uncertainty, and ensuring every interconnect met the strict signal-integrity requirements of 800 G networks.
