The data rates flowing through today's connectors would have been difficult to imagine a decade ago. Where engineers once wrestled with signal quality at 6 Gbps, the industry now designs and validates interconnects at 112 Gbps, 224 Gbps, and beyond. But this leap did not happen overnight. Before a high-speed connector can be tested — let alone trusted in production — the surrounding technology ecosystem must reach the necessary level of maturity. That level of industry maturity now enables high-speed connector development and validation at data rates that were previously impractical to characterize reliably.
The Simulation Revolution
Characterizing a connector at 25+ Gbps demands far more than measuring insertion loss. It requires modeling the complete signal path — transmitter equalization, package parasitics, PCB traces, vias, connector geometry, and receiver response — as a unified channel. A decade ago, this end-to-end analysis was painstaking and often unreliable as simulation tools struggled to correlate with real-world measurements at higher frequencies.
That gap has closed considerably.
Synopsys PrimeSim HSPICE, widely used for high-speed circuit simulation, now integrates with MATLAB’s Signal Integrity Toolbox to support full-channel statistical and time-domain analysis, including feed-forward equalization (FFE), CTLE, DFE, and clock-data recovery modeling.
Ansys HFSS offers the 3D electromagnetic field solution necessary to accurately model connector and via structures. These tools now work with IBIS-AMI behavioral models of actual SerDes silicon, enabling engineers to predict link performance at bit error rates as low as 10⁻¹³ — the MAC-layer target for next-generation Ethernet —
Standards Driving the Pace
The IEEE 802.3 family of Ethernet standards has been a main driver behind the industry's progress at each speed milestone. The 802.3ap specification, ratified in 2007, introduced the insertion-loss-to-crosstalk ratio (ICR) metric, which provided connector designers with a clear, measurable performance goal — one Hirose adopted early as a benchmark for validating our IT5 and IT8 connector families. Later standards raised the bar: 802.3bj in 2014 defined 25 Gbps per lane for 100 Gigabit Ethernet, 802.3cd in 2018 pushed to 50 Gbps per lane, and 802.3ck — approved in September 2022 — established 100 Gbps per lane signaling for today's 400G and 800G Ethernet links.
Now, IEEE 802.3dj is defining 200 Gbps per lane for 1.6 Tbps Ethernet, with a final standard targeted for late 2026. PCI-SIG released PCIe Gen 6 in January 2022 at 64 GT/s — a protocol Hirose's IT8 Series directly supports through its Polarity-Swap FEXT canceling technology and highest-in-market signal density — and is driving toward PCIe Gen 7 at 128 GT/s using PAM4 signaling.
Each new standard increases more than bandwidth. It also tightens channel tolerances, introduces additional compliance metrics such as channel operating margin (COM) and effective return loss (ERL), and requires every component in the signal path — including connectors — to meet stricter performance targets.
Test Equipment Catches Up
Standards are only meaningful if they can be verified. Rohde & Schwarz now provides automated compliance testing solutions with its ZNrun VNA automation suite, testing cable assemblies against IEEE 802.3ck and upcoming 802.3dj specifications — automating measurement, post-processing, and pass/fail analysis. Keysight Technologies delivers conformance testing solutions for 100G per lane and is developing tools for 200G per lane. Anritsu's Signal Quality Analyzer-R MP1900A supports 64 Gbaud PAM4 pattern generation and error detection, while its VectorStar ME7838AX broadband VNA allows S-parameter measurement up to 125 GHz — bandwidth now essential for validating 224 Gbps and 448 Gbps interconnects.
This generation of test equipment enables Hirose and our customers to validate connector performance with a level of precision that was not possible with earlier generations of high-speed interconnects.
The NRZ-PAM4 Inflection
Perhaps the most significant enabling shift has been the move from NRZ (non-return-to-zero) to PAM4 (pulse amplitude modulation with four levels) signaling. At 28 Gbps NRZ, the Nyquist frequency sits at 14 GHz — within the characterization bandwidth of existing tools and materials. Doubling to 56 Gbps NRZ would push that to 28 GHz, straining PCB materials, copper roughness budgets, and measurement equipment alike.
PAM4 addressed this limitation by encoding two bits per symbol, effectively doubling throughput without doubling required bandwidth. A 56 Gbps PAM4 signal operates at 28 Gbaud — the same symbol rate as 28 Gbps NRZ. However, PAM4 introduces its own challenges: stricter signal-to-noise requirements, more complex
At 224 Gbps PAM4 (112 Gbaud), traditional FR-4 PCB materials are no longer sufficient, and even advanced low-loss laminates are strained to their limits. Copper roughness, once a secondary concern, has become the dominant loss mechanism on low-loss substrates. Hirose's next-generation IT16 Series, which supports PAM4 applications with an industry-leading 46 mm stacking height, is designed for this environment.
The Industry is Ready
The convergence of advanced simulation tools, evolving standards, modern signaling methods, and precision measurement equipment has fundamentally changed how high-speed connectors are designed and validated. What once pushed the limits of characterization can now be modeled, tested, and verified with a level of accuracy that enables reliable operation at 25+ Gbps and beyond.
These advancements continue to influence how Hirose develops and validates next-generation high-speed interconnects.
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