Fiber-to-the-processor requires controlled technology transition

• Electronics driven to design-point (slow-wide) which does not provide natural transition to fiber-optic interconnects (fast-narrow)

• 0.1 mm CMOS design trade-off

  • Bi-directional saves I/O pins and is favored by electrical interconnects
    • Single-ended electrical
      • 1-pin
        • multi-level signaling can give simultaneous Tx and Rx
        • noise, reference circuitry and reflections limit signaling rate
      • Differential electrical
        • 2-pins
          • improved immunity to noise
        • Challenge is 5 Gb/s/pin circuit design for bi-directional electrical
          • Design of broad-band reference circuitry
          • Impedance matching
          • End-to-end signal integrity (IC, package, PCB)
        • Uni-directional is natural choice for fiber-optic interface
          • Single-ended electrical
            • 2-pins
              • noise
            • Differential electrical
              • 4-pins
                • robust signaling at 10 Gb/s
                • minimum latency
                • minimum logic and control signals
                • no buffering
                • compatibility with optical interconnect solutions

Electrical

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