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Silicon photonics

Even as photonics-electronics convergence advances, why is electrical wiring expected to remain in use for very short links such as those inside a chip?

  1. ALight has higher propagation loss over shorter distances
  2. BOptical fibers and waveguides cannot be cut or made short
  3. COptical transmission requires electrical-optical conversion, whose power and latency can exceed the loss of a short electrical wire
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Answer: C. Optical transmission requires electrical-optical conversion, whose power and latency can exceed the loss of a short electrical wire

Sending a signal optically requires converting electricity to light at the transmitter (modulation) and back at the receiver (detection and amplification), each adding power and latency. Electrical wiring loss grows with distance, so optics wins over long distances, but over very short distances the conversion overhead can be larger. The goal of photonics-electronics convergence is to raise conversion efficiency and shorten the distance at which optics pays off.

  • A. Optical propagation loss is proportional to length and is smaller for shorter links.
  • B. Silicon waveguides can be made just a few micrometers long.
  • C. Correct. Over short distances the conversion overhead may not pay off.
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More Silicon photonics questions

  1. In long-haul optical fiber communication, what is the main reason wavelengths around 1.55 µm (C-band) are widely used?
  2. For relatively short-reach optical links inside data centers, which is a correct reason wavelengths around 1.31 µm (O-band) are often used?
  3. Which correctly pairs the photon energy of 1.55 µm light with its behavior in a silicon waveguide? (E [eV] ≈ 1.24 / λ [µm])
  4. Which correctly describes a silicon waveguide (refractive index about 3.5) surrounded by oxide (SiO2, refractive index about 1.45)?
  5. When light travels from silicon (refractive index 3.48) toward oxide (refractive index 1.45), which is closest to the critical angle for total internal reflection (measured from the normal to the interface)?

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