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Towards an optical FPGA – Programmable silicon photonic circuits [pdf]

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Re: Towards an optical FPGA – Programmable silicon photonic circuits [pdf]

#31

Post by alvesjnr »

awestroke wrote: post #4
alvesjnr wrote: post #2

Hi, I'm the author of this paper [15] cited in OP's publication. We are the author of the very first implementation of a fully programmable optical linear circuit in silicon. This is the basic building block to have an optical processor (in this specific architecture). Ask me anything. [15] - http://www.photonics.intec.ugent.be/download/pub_3834.pdf

How large is your proof of concept implementation? Do you think the architecture could be miniaturised enough to make a whole processor?

The full optical device is no bigger than 1mm x 0.5mm. It's very tiny in total size.

The point here is that our current implementation has a limited IO capability (our linear operator has 4 inputs and 4 outputs), but increasing the number of IOs leads to a linear increase in the size of the device.

Re: Towards an optical FPGA – Programmable silicon photonic circuits [pdf]

#32

Post by alvesjnr »

freyir wrote: post #13
alvesjnr wrote: post #2

Hi, I'm the author of this paper [15] cited in OP's publication. We are the author of the very first implementation of a fully programmable optical linear circuit in silicon. This is the basic building block to have an optical processor (in this specific architecture). Ask me anything. [15] - http://www.photonics.intec.ugent.be/download/pub_3834.pdf

I'm not very familiar with the subject, but I've been hearing about academic work on optical integrated circuits for a few years now. Is this work being commercialized yet? Are there photonic ICs in use in industry?

Hi,

Photonics ICs are all around. You can find it in many different applications, but mostly in datacom and telecom.

A very simple example: anywhere you have a optical fiber you also need a photonic IC to, at least, convert the light into electrical signal to interface your electronics (and vice-versa).

What we are doing with photonics is adding more functionality in the optical part (filtering signal, multiplexing, modulation, etc) once, in mostly cases, it's more efficient doing that in the optical domain instead of using electronics.

Re: Towards an optical FPGA – Programmable silicon photonic circuits [pdf]

#33

Post by alvesjnr »

andy_ppp wrote: post #7
alvesjnr wrote: post #2

Hi, I'm the author of this paper [15] cited in OP's publication. We are the author of the very first implementation of a fully programmable optical linear circuit in silicon. This is the basic building block to have an optical processor (in this specific architecture). Ask me anything. [15] - http://www.photonics.intec.ugent.be/download/pub_3834.pdf

Could you foresee fully photonic hardware at some point so not just silicon but motherboards, graphics cards and even external interconnects? Is it possible to build RAM and SSDs in optical circuits yet? I ask because this has very interesting military uses that could push this forward if you could have devices impervious to electro-magnetic pulses.

I don't see photonics doing the data processing anytime soon. For that our current electronics works just fine.

What we do with photonics is to improve areas where the electronics is not efficient.

Case and point: interconnections. If you want to move data from point A to point B (being A and B either two different chips in your board our two datacenters), we can do it using electric signals, it works just fine, but at some cost. Electric signals dissipate power when they travel through a conductor, no matter how good the conductor is.

If instead we use optical signals instead of electrical, we have advantage in a number of points, specially power efficiency.

Re: Towards an optical FPGA – Programmable silicon photonic circuits [pdf]

#34

Post by alvesjnr »

jacquesm wrote: post #5
alvesjnr wrote: post #2

Hi, I'm the author of this paper [15] cited in OP's publication. We are the author of the very first implementation of a fully programmable optical linear circuit in silicon. This is the basic building block to have an optical processor (in this specific architecture). Ask me anything. [15] - http://www.photonics.intec.ugent.be/download/pub_3834.pdf

Fantastic work. Some off-hand questions, total noob in your field but interested in it and reading a lot: - how fast is it (4KHz mentioned seems a bit slow, or is that a function of size?)? - how far away from practical applications do you think you are? - is the optical circuitry limited by the interaction with the electronic parts? - the paper is already two years old, have there been interesting developments since…

The concept of speed that we use in a digital computer does not automatically applies to our optical circuit once we don't work using cycles of a clock. It's not a digital computer, but an operator that realizes a linear operation on an input. The speed of this operation is only bounded by the speed of the light propagating though the circuit.

We have optical chips in operation everywhere for decades, that's not something new. An programmable optical chip has been demonstrated by different research groups, and, for some limited applications, I do believe that we will have it in the marked in 7 to 10 years.

We are also working on different topologies besides the one mentioned in the paper.

Re: Towards an optical FPGA – Programmable silicon photonic circuits [pdf]

#35

Post by alvesjnr »

georgeburdell wrote: post #11
alvesjnr wrote: post #2

Hi, I'm the author of this paper [15] cited in OP's publication. We are the author of the very first implementation of a fully programmable optical linear circuit in silicon. This is the basic building block to have an optical processor (in this specific architecture). Ask me anything. [15] - http://www.photonics.intec.ugent.be/download/pub_3834.pdf

Could you explain, or maybe point to a good textbook with a chapter on the subject, why the coupling efficiency to the second waveguide on the directional coupler peaks at a certain intermediate waveguide length? I have a PhD, just not in photonics.

I'll try an ELI5:

When the light propagates in a waveguide as the one used in my circuit, the E and H components of the EM wave are not fully confined to the waveguide, but part of it stays outside the waveguide. If you put two waveguides close to each other and makes the light travel to the first waveguide, part of the EM field of the light will also see the second waveguide.it makes part of the ligh couple to the second waveguide. As the wave travels, more and more light couples to the second waveguide. If you engineer it well, at some point 50% of the light will be confined in each waveguide. At this point you separate both WG and you have a 50:50 coupler.

Re: Towards an optical FPGA – Programmable silicon photonic circuits [pdf]

#36

Post by alvesjnr »

wean_irdeh wrote: post #28
alvesjnr wrote: post #2

Hi, I'm the author of this paper [15] cited in OP's publication. We are the author of the very first implementation of a fully programmable optical linear circuit in silicon. This is the basic building block to have an optical processor (in this specific architecture). Ask me anything. [15] - http://www.photonics.intec.ugent.be/download/pub_3834.pdf

How far are we from just using photon to run our computer instead of primarily relying to electron/electricity? Is there anything that prevent a turing complete system that uses light/optic/photon to run instead of primarily using electron/electricity?

Not even close.

Photonics chips and programable photonics are not a way to substitute conventional electronics, but a replacement/complement for some areas of the field where electronics is not efficient.

Re: Towards an optical FPGA – Programmable silicon photonic circuits [pdf]

#37

Post by alvesjnr »

raverbashing wrote: post #8
alvesjnr wrote: post #2

Hi, I'm the author of this paper [15] cited in OP's publication. We are the author of the very first implementation of a fully programmable optical linear circuit in silicon. This is the basic building block to have an optical processor (in this specific architecture). Ask me anything. [15] - http://www.photonics.intec.ugent.be/download/pub_3834.pdf

How is the optical switching power needs being addressed? Last I heard, you needed a high-powered laser on a non-linear material to turn transmission of a separate light signal on/off. Is that how things still work?

One main point to take for the analyses is that photons are bosons, so they don't interact between each other, which makes optical switches a pretty hard thing to do.

What we do is using interference to make a switch. More specifically, we use an apparatus called Mach-Zehnder interferometer (combined with a phase shifter) to manipulate the light.

Re: Towards an optical FPGA – Programmable silicon photonic circuits [pdf]

#38

Post by jacquesm »

alvesjnr wrote: post #34
jacquesm wrote: post #5

Earlier quoted context omitted.

Fantastic work. Some off-hand questions, total noob in your field but interested in it and reading a lot: - how fast is it (4KHz mentioned seems a bit slow, or is that a function of size?)? - how far away from practical applications do you think you are? - is the optical circuitry limited by the interaction with the electronic parts? - the paper is already two years old, have there been interesting developments since…

The concept of speed that we use in a digital computer does not automatically applies to our optical circuit once we don't work using cycles of a clock. It's not a digital computer, but an operator that realizes a linear operation on an input. The speed of this operation is only bounded by the speed of the light propagating though the circuit. We have optical chips in operation everywhere for decades, that's not some…

Thank you!

Re: Towards an optical FPGA – Programmable silicon photonic circuits [pdf]

#39

Post by georgeburdell »

alvesjnr wrote: post #35
georgeburdell wrote: post #11

Earlier quoted context omitted.

Could you explain, or maybe point to a good textbook with a chapter on the subject, why the coupling efficiency to the second waveguide on the directional coupler peaks at a certain intermediate waveguide length? I have a PhD, just not in photonics.

I'll try an ELI5: When the light propagates in a waveguide as the one used in my circuit, the E and H components of the EM wave are not fully confined to the waveguide, but part of it stays outside the waveguide. If you put two waveguides close to each other and makes the light travel to the first waveguide, part of the EM field of the light will also see the second waveguide.it makes part of the ligh couple to the s…

Yes I know that the mode isn't perfectly confined in the waveguide, but Figure 4(b) of the article shows the coupling efficiency to the second waveguide going down as the length of the intermediate waveguide gets longer past some critical value. That's the part that gets me.
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