3 ms·

How about photonic circuits?

by sydthrowaway 4y ago

simonh 4y ago
They're still at the basic research stage, with no real path to practical applications yet.
- sydthrowaway 4y ago
  Still? It's been thirty years
  - simonh 4y ago
    The latest news was development of an optical transistor, but the output signal is electrical, not optical. That would make chaining them to make a logic gate tricky.
galcerte 4y ago
You can't transmit large amounts of power through a photonic circuit, so forget about using them to replace power electronics.
- sydthrowaway 4y ago
  How about for information?
  - galcerte 4y ago
    Of course you can. Otherwise we wouldn't use fiber optics everywhere. You only need a teeny tiny amount of power transmitted to carry a distinguishable signal after all.
FunnyBadger 4y ago
Photonics doesn't buy you much. The primarily limit on speed in large chips like processors is NOT the transistors but the transmission lines connecting the transistors. And those are already operating at 50%-75% of the speed of light. The gain going to photonics doesn't justify the cost at this point. Another factor: pretty much EVERYTHING in current microelectronics gets dumped in the garbage if you were to 100% switch to photonics and that's a step too far. There is relatively little in electronics that can be leveraged to photonics. In general you need about 80% overlap with the prior major technology to justify a jump that big. This was true of tubes to transistors, and then transistors to ICs. You'd see the exact same circuit used in the prior technology being repurposed to the new one - almost verbatim. And it's that leverage that justifies the inevitable higher cost of any new technology - at least you can re-use designs, skills and concepts.
- tlb 4y ago
  Chip interconnect is much slower than that over long distances. In addition to the LC delay you mention, the RC delay is substantial and increases as the square of distance so it dominates for long wires. The distance-squared effect is mitigated by adding repeaters along the way, but they add their own delay. Overall wire speeds of 40 ps / mm are typical, about 8% of the speed of light.

How about photonic circuits?

simonh 4y ago

They're still at the basic research stage, with no real path to practical applications yet.

sydthrowaway 4y ago
Still? It's been thirty years
- simonh 4y ago
  The latest news was development of an optical transistor, but the output signal is electrical, not optical. That would make chaining them to make a logic gate tricky.

galcerte 4y ago

You can't transmit large amounts of power through a photonic circuit, so forget about using them to replace power electronics.

sydthrowaway 4y ago
How about for information?
- galcerte 4y ago
  Of course you can. Otherwise we wouldn't use fiber optics everywhere. You only need a teeny tiny amount of power transmitted to carry a distinguishable signal after all.

FunnyBadger 4y ago

Photonics doesn't buy you much. The primarily limit on speed in large chips like processors is NOT the transistors but the transmission lines connecting the transistors. And those are already operating at 50%-75% of the speed of light. The gain going to photonics doesn't justify the cost at this point. Another factor: pretty much EVERYTHING in current microelectronics gets dumped in the garbage if you were to 100% switch to photonics and that's a step too far. There is relatively little in electronics that can be leveraged to photonics. In general you need about 80% overlap with the prior major technology to justify a jump that big. This was true of tubes to transistors, and then transistors to ICs. You'd see the exact same circuit used in the prior technology being repurposed to the new one - almost verbatim. And it's that leverage that justifies the inevitable higher cost of any new technology - at least you can re-use designs, skills and concepts.

tlb 4y ago
Chip interconnect is much slower than that over long distances. In addition to the LC delay you mention, the RC delay is substantial and increases as the square of distance so it dominates for long wires. The distance-squared effect is mitigated by adding repeaters along the way, but they add their own delay. Overall wire speeds of 40 ps / mm are typical, about 8% of the speed of light.