Page 37 - 2020 Interconnect Innovations eBook

To combat this and enable usable trace lengths at higher data rates, multiple retimers and/or optical clock and data recovery circuits are often required every few inches along the signal path. In short, routing today’s high-speed signals in a PCB is challenging and expensive.
How do we increase data rates while simultaneously combatting the physical limitations of doing so?
The Flyover® Cable System for 112Gb/s PAM4 Solutions
An alternative approach, already implemented by many system architects, provides lower loss, longer reach, and improved system flexibility by routing signals over the PCBs instead of through them. This is accomplished using low-loss, low-skew micro-twinax cable systems.
Micro-twinax cables, high-speed connectors, and design, assembly, and routing techniques that optimize performance, combine to make these cable systems a viable alternative. Figure 3 illustrates the difference of low- skew, micro-twinax cables versus traditional PCB laminate materials. Low-skew twinax cables improved insertion loss performance versus MEGTRON6 and MEGTRON7 at a Nyquist frequency of 28GHz (112Gb/s PAM4 or 56Gb/s NRZ). The difference at a Nyquist frequency of 56GHz (which is not shown on the chart) is even wider, offering a path to 112Gb/s and even 224Gb/s PAM4 system performance.
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» Figure 3: Insertion loss of low-loss, micro-twinax cable and verious PCB laminate materials
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