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For a switch with a total bandwidth of 51.2 Tb/s, if all optical links operate at 5 pJ per bit, which is closest to the power consumption of the optical links?

  1. AAbout 256 W
  2. BAbout 26 W
  3. CAbout 2.6 kW
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Answer: A. About 256 W

Power consumption is energy per bit × bit rate: 5×10⁻¹² J/bit × 51.2×10¹² b/s = 256 W. The optical links alone reach several hundred W, so lowering pJ/bit even slightly is important for limiting overall data center power. For example, reducing energy per bit from 15 pJ to 5 pJ saves about 500 W at the same bandwidth. CPO and linear drive aim to lower pJ/bit by reducing the power spent on long electrical paths and DSPs. Watch out for mixing up prefixes such as T and G, or p and n.

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