This is a live demonstration of 112 Gbps PAM4 traffic using Credo Semiconductors mixed signal SERDES with Samtec Flyover technology.
First, Jignesh walks us through the signal path:
- A Credo Firebird SERDES generates 31-bit PRBS data at 112 Gbps PAM4 data rates.
- The signals travel from the Credo test board, through precision RF cable assemblies,
- To a Samtec NovaRay™ cable assembly SI evaluation board.
- The signals route through the NovaRay board, to a NovaRay cable assembly,
- Then through 12” of 34 AWG Eye Speed® Ultra Low Skew Twinax Cable.
- The signals then travel through the cable to a double density Samtec Flyover QSFP28 cable connector,
- the FQSFP-DD series and cage signals then route through Samtec’s QSFP-DD SI Characterization board,
- Through another set of precision RF cable assemblies,
- To a Credo Pelican II receive SERDES chip, where we collect BER results
This entire system represents a complete VSR link from chip to module with over 18” of reach.
By the way, we chose 34 AWG cable because it is optimal for signal integrity performance and cable management in high density applications.
The results are impressive: The insertion loss of 34 AWG twinax cable is only 0.27 dB/inch at 112 Gbps PAM4. The transmit and receive eye diagrams show PAM4 modulation. Using Credo’s user interface, we can look at the eye heights; all are greater the 125 mV.
The bit error ratio of the entire system is 8e-09 pre-FEC, which is 4 – 5 orders of magnitude better than the spec.
This demonstration illustrates the advantages of the Samtec Flyover and NovaRay systems. Here’s a link explaining the strategies and benefits of Samtec Flyover.