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TSMC bets on unorthodox optical tech
- Liftyee 1y agoAs I understand it (from designing high-speed electronics), the major limitations to data/clock rates in copper are signal integrity issues. Unwanted electromagnetic interactions all degrade your signal. Optics is definitely a way around this, but I wonder if/when it will ever hit similar limits.
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- moelf 1y agoluckily photons are boson (if we ever pushes things to this level of extreme)
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- Taek 1y agoThis comment appears insightful but I have no idea what it means. Can someone elaborate?
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- scheme271 1y agoElectrons are fermions which means that two electrons can't occupy the same quantum state (Pauli exclusion principle). Bosons don't have the limit so I believe that implies that you can have stronger signals at the low end since you can have multiple photons conveying or storing the same information.
- xeonmc 1y agoAlso less chance for external interference.
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- cycomanic 1y agoWhat the previous poster is implying is that electrons interact much more strongly than photons. Hence electrons are very good for processing (e.g. building a transistor), while photons are very good for information transfer. This is also a reason why much of the traditional "optical computer" research was fundamentally flawed, just from first principles one could estimate that power requirements are prohibitive.
- nullc 1y ago> This is also a reason why much of the traditional "optical computer" research was fundamentally flawed presumably also because photons at wavelengths we can work with are BIG
- xeonmc 1y agoFermions can “hit each other” whereas bosons “pass through each other”. (Strong emphasis on the looseness of the scare quotes.)
- EA-3167 1y agoThe energy densities required for photon-photon interactions are so far beyond anything we need to worry about that it's a non-issue. Photons also aren't going to just ignore local potential barriers and tunnel at the energy levels and scales involved in foreseeable chip designs either.
- wyager 1y agoP-p interactions are not an issue but we do have high enough field intensities in high bandwidth fibers to run into p-f nonlinearity issues.
- notepad0x90 1y agoisn't attenuation also an issue with copper? maybe with small electronics it is negligible given the right amps? in other words, with with no interference, electrons will face impedance and start losing information.
- to11mtm 1y agoAttenuation is going to be an issue for any signal, but in my experience Fiber can go for many miles without a repeater whereas something like Coax you're going one to two orders of magnitude less. [0] [0] - Mind you, some of that for Coax is due to other issues around CTB and/or the challenge that in Coax, you've got many frequencies running through alongside each frequency having different attenuation per 100 foot...
- spwa4 1y ago> Coax is due to other issues around CTB and/or the challenge that in Coax, you've got many frequencies running through alongside each frequency having different attenuation per 100 foot Actually this is true for fibers as well. In DWDM (all internet links are DWDM, including fiber-to-the-home in most places) you have many frequencies running alongside and each frequency has differences in attenuation (though generally measured per kilometer, not 100 foot) Optical light are standing electromagnetic waves. Which means they don't disrupt each other. Electrical signals aren't standing waves. They affect each other. The difference can be put like this: how many X (electrical waves, but essentially everything, protons, ...) fit on the tip of a needle? (or in a cable) 1) electrical waves? Some finite number. Can be large of course, but ... 2) photons (ie. fiber signals)? ALL OF THEM. Literally every photon that exists in the entire universe would happily join every other photon on the tip of a needle nothing would interfere with anything else
- bgnn 1y agoThis is the main mechanism of interference anyhow, called inter-symbol-interference.
- lo0dot0 1y agoOptics also have signal integrity issues. In practice OSNR and SNR limit optics. Cutting the fiber still breaks it. Small vibrations also affect the signal's phase.
- cycomanic 1y agoPhase variations will not introduce any issues here, they most certainly are talking about intensity modulation. You can't really (easily) do coherent modulation using incoherent light sources like leds. SNR is obviously an issue for any communication system, however fiber attenuation is orders of magnitude lower than coax. The bigger issues in this case would be mode-dispersion, considering that they are going through "imaging" fibres, i.e. different spatial components of the light walking off to each other causing temporal spread of the pulses until they overlap and you can't distinguish 1's and 0's.
- abdullahkhalids 1y agoMode dispersion is frequency dependent phase changes.
- cycomanic 1y agoThat's chromatic dispersion, mode dispersion is spatial "path" dependent phase changes. Vibration is actually somewhat more relevant because if it wasn't for that we could theoretically undo mode dispersion (we would need phase information though). That said all of that is irrelevant to what the previous speaker said, vibration induced phase variation as an impairment. Thats just not an issue, vibrations are way too slow to impair optical comms signals.
- mycall 1y agoHow do the gravity wave optical paths solve the vibration issues? Couldn't TSMC do something similar?
- BardiaPezeshki 1y ago
- wyager 1y agoWe already regularly run into optical nonlinearity issues in submarine cables. The instantaneous EM fields generated in high bandwidth fiber are sufficiently strong to cause nonlinear interactions with the fiber medium that we have to correct for.
- Salgat 1y agoI don't believe this is a factor for the distances that inter-chip transmission has. From what I can find, this is at most an issue for communication spanning tens to hundreds of meters in a datacenter.
- m3kw9 1y agoIf each cable is 10gb/s and uses 1 pixel to convert into electrical signals, would that mean they need a 10 giga frame per second sensor?
- cpldcpu 1y agoI think that's just a simplifying example. They would most likely not use an image sensor, but a photodetector with a broadband amplifier.
- lo0dot0 1y agoNo, not necessarily. If you can distinguish different amplitude levels you can do better. For example four amplitude modulation (4AM) carries two bits per symbol. There is also the option to use coherent optics, which can detect phase, and carry additional information in the phase.
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- amelius 1y ago> The transmitter acts like a miniature display screen and the detector like a camera. So if I'm streaming a movie, it could be that the video is actually literally visible inside the datacenter?
- tehjoker 1y agomaybe a low res bit packed binary motion picture thats uncompressed
- tails4e 1y agoNo, this is just an a analogy. The reality is the data is heavily modulated, and also the video is encoded so at no point would something that visually looks like an image be visible in the fibre.
- lo0dot0 1y agoObviously this is not how video compression and packets work but for the sake of the argument consider the following. The article speaks of a 300 fiber cable. A one bit per pixel square image with approx. 300 pixels is 17x17 in size. Not your typical video resolution.
- fecal_henge 1y agoNot your typical frame rate either.
- mystified5016 1y agoNot any more than if you blinked an LED each time a bit comes across your network connection.
- topspin 1y agoThey story states there are 300 optical lines in the "fiberbundle." Let's assume this is arranged as 20x15 and the wavelength of the led is visible and bright enough to perceive. So if your unencoded, monochrome 20x15 movie was aligned on every frame and rendered at 10E9 FPS, then yes, your movie would be visible at the end of one of these cables through a magnifying glass.
- speedbird 1y agoHeadline seems misleading. They’re buildings detectors for someone, not ‘betting’ on it.
- ggm 1y agoThe word is mostly used for finance investment promotion. I'd guess that it's written to attract those bloggers/casters, and make money for somebody.
- walthamstow 1y agoThe 'bet' is investing time and money into something that may not yield results. It's pretty common business language.
- ls612 1y agoForgive the noob question but what stops us from making optical transistors?
- qwezxcrty 1y agoI think the most fundamental reason is that there is no efficient enough nonlinearity at optical frequencies. So two beams(or frequencies in some implementation) tends not to affect each other in common materials, unless you have a very strong source (>1 W) so the current demonstrations for all-optical switching are mostly using pulsed sources.
- ls612 1y agoI wonder if considerably more engineering and research effort will be applied here when we reach the limit of what silicon and electrons can do.
- cycomanic 1y agoNo this is not an engineering issue, it's a problem of fundamental physics. Photons don't interact easily. That doesn't mean there are not specialised applications where optical processing can make sense, e.g. a matrix multiplication is really just a more complex lens so it's become very popular to make ML accelerators based on this.
- momoschili 1y agoContrary to the prior commenter, there is definitely significant engineering going toward this, but it's not clear or likely that photonic computing will supplant electronic computing (at least not anytime soon), but rather most seem to think of it as an accelerator for highly parallel tasks. Two major ways people are thinking of achieving this are using lithium niobate devices which mediate nonlinear optical effects via light-matter interaction, and silicon photonic devices with electrically tunable elements. In the past there was a lot of work with III-V semiconductors (GaAs/InAs/GaN/AlN etc) but that seems to have leveled off in favor of lithium niobate. Photonics has definitely proved itself in communications and linear computing, but still has a way to in terms of general (nonlinear) compute.
- qwezxcrty 1y agoNot an expert in communications. Would the SerDes be the new bottleneck in the approach? I imagine there is a reason for serial interfaces dominating over the parallel ones, maybe timing skew between lanes, how can this be addressed in this massive parallel optical parallel interface?
- to11mtm 1y ago> timing skew between lanes That's a big part of it. I remember in the Early Pentium 4 days, starting to see a lot more visible 'squiggles' on PCB traces on motherboards; the squiggles essentially being a case of 'these lines need more length to be about as long as the other lines and not skew timing' In the case of what the article is describing, I'm imagining a sort of 'harness cable' that has a connector on each end for all the fibers, and the fibers in the cable itself are all the same length, there wouldn't be a skew timing issue. (Instead, you worry about bend radius limitations.) > Would the SerDes be the new bottleneck in the approach I'd think yes, but at the same time in my head I can't really decide whether it's a harder problem than normal mux/demux.
- fecal_henge 1y agoSerDes is already frequently parallelised. The difference is you never expect the edges or even the entire bits to arrive at the same time. You design your systems to recover timing per link so the skew doesnt become the constraint on the line rate.
- bgnn 1y agoone can implement SerDes at any point of the electro-optical boundary. For example, if we have 1 Tbps incoming NRZ data from the fiber, and the CMOS technology at hand only allows 10 GHz clock speed for the slicers, one can have 100x receivers (photodiode, TIA, slicer), or 1x photodiode, 100x TIA + slicer, or 1x photodiode + TIA and 100x slicers. The most common id the last one, and it spits out 100x parallel data. Things get interesting if the losses are high and there needs to be a DFE. This limits speed a lot, but then copper solutions moved to sending multi-bit symbols (PAM 3, 4,5,6,8,16.. ) which can also be done in optical domain. One can even send multiple wavelengths in optical domain, so there are ways to boost the baud rate without requiring high clock frequencies.
- cycomanic 1y agoThat article is really low on details and mixes up a lot of things. It compares microleds to traditional WDM fiber transmission systems with edge emitting DFB lasers and ECLs, but in datacentre interconnects there's plenty of optical links already and they use VCSELs (vertical cavity surface emitting lasers), which are much cheaper to manufacture. People also have been putting these into arrays and coupling to multi-core fiber. The difficulty here is almost always packaging, i.e. coupling the laser. I'm not sure why microleds would be better. Also transmitting 10 Gb/s with a led seems challenging. The bandwidth of an incoherent led is large, so are they doing significant DSP (which costs money and energy and introduces latency) or are they restricting themselves to very short (10s of m) links?
- tehjoker 1y agoshort links it’s in the article
- cycomanic 1y agoAh I missed the 10m reference there. I'm not sure it makes more sense though. Typical intra-datacenter connections are 10s-100s of meters and use VCSELs, so introducing microleds just for the very short links instead of just parallelising the VCSEL connections (which is being done already)? If they could actually replace the VCSEL I would sort of see the point.
- jauntywundrkind 1y agoThere's been a constant drum-beat that even intra-rack is trying to make its way to optical as fast as it can, that copper is more and more complex and expensive to scale faster. If we have a relatively affordable short range optical system that doesn't require heavy computational work to do, that sounds like a godsend, like a way to increase bits per joule while reducing expensive cabling cost. Sure yes, optical might use expensive longer range optical today! But using that framing to assess new technologies & what help the could be may be folly.
- qwezxcrty 1y ago
- albertzeyer 1y agoThere is also optical neuromorphic computing, as an alternative to electronic neuromorphic computing like memristors. It's an fascinating field, where you use optical signals to perform analog computing. For example: https://www.nature.com/articles/s41566-020-00754-y https://www.nature.com/articles/s41566-020-00754-y https://www.nature.com/articles/s44172-022-00024-5 https://www.nature.com/articles/s44172-022-00024-5 As far as I understood, you can only compute quite small neural networks until the noise signal gets too large, and also only a very limited set of computations works well in photonics.
- cycomanic 1y agoThe issue with optical neuromorphic computing is that the field has been doing the easy part, i.e. the matrix multiplication. We have known for decades that imaging/interference networks can do matrix operations in a massively parallel fashion. The problem is the nonlinear activation function between your layers. People have largely been ignoring this, or just converted back to electrical (now you are limited again by the cost/bandwidth of the electronics).
- seventytwo 1y agoSeems hard to imagine there’s not some non-linear optical property they could take advantage of
- cycomanic 1y agoThe problem is intensity/power, as discussed previously photon-photon interactions are weak, so you need very high intensities to get a reasonable nonlinear response. The issue is, that optical matrix operations work by spreading out the light over many parallel paths, i.e. reducing the intensity in each path. There might be some clever ways to overcome this, but so far everyone has avoided that problem. They said we did "optical deep learning" what they really did was an optical matrix multiplication, but saying that would not have resulted in a Nature publication.
- programjames 1y ago
- smj-edison 1y agoWith this design, how do they route enough pins from the chip to the optical transceiver? Would it take chiplets to get enough lanes?
- nsteel 1y agoThere's a link to their press release in the article, it probably answers some questions here: https://avicena.tech/avicena-announces-modular-lightbundle-optical-interconnect-platform-with-1tbps-mm-i-o-density-and-1pj-bit/ https://avicena.tech/avicena-announces-modular-lightbundle-o...
- rajnathani 1y agoMinor: It would be nice if the company TSMC is collaborating with on this, Avicena, is mentioned in the HN title.
- stingraycharles 1y agoIt’s against HN policy to editorialize the titles
- rajnathani 1y agoBut it is also against HN rules to keep sensationalistic titles, dang (moderator 1) routinely modifies titles wherever necessary.
- deleted 1y ago[deleted]
- sunray2 1y agoSomewhat related: there's a relatively big push for optical interconnects and integrated optics in quantum computing. Maybe this article yields insight onto what may happen in future. With quantum computing, one is forced to use lasers. Basically, we can't transmit quantum information with the classical light from LEDs (handwaving-ly: LEDs emit a distribution of possible photon numbers, not single photons, so you lose control at the quantum level). Moreover, we often also need the narrow linewidth of lasers, so that we can interact with atoms in the way we want them to. That is, not to excite unwanted atomic energy levels. So you see in trapped ion quantum computing people tripping over themselves to realise integration of laser optics, through fancy engineering that i don't fully understand like diffraction gratings within the chip that diffract light onto the ions. It's an absolutely crucial challenge to overcome if you want to make trapped ion quantum computers with more than several tens of ions. Networking multiple computers via said optical interconnects is an alternative, and also similarly difficult. What insight do i gleam from this IEEE article, then? I believe if this approach with the LEDs works out for this use case, then I'd see it as a partial admission of failure for laser-integrated optics at scale. It is, after all, the claim in the article that integrating lasers is too difficult. And then I'd expect to see quantum computing struggle severely to overcome this problem. It's still research at this stage, so let's see if Nature's cards fall fortuitously.
- avsteele 1y agoTSMC's approach here sounds sensible but I don't think it speaks much to QC. It is a pretty different problem domain. The trapped-ion QCs can use much more expensive / less practical lasers and optics and still be useful.
- mmmBacon 1y agoQuantum computing is still a technology of the future. When we are still talking about 12 qubits as a breakthrough, there’s a long way to go. Optical interconnects are the least of quantum computing’s problems. However, it’s not correct to say lasers are unreliable. It’s fundamentally false and it’s not supported by field data from today’s pluggable modules. 10’s of millions of lasers are deployed in data centers today in pluggable modules. It’s also useful to remember that an LED is essentially the gain region of a laser without the reflectors. When lasers fail in the field, they fail for the same reasons an LED will fail; moisture or contamination penetration of the semiconductor material. An LED is not useful for quantum computing. To create a Bell pair (2qubits) you need a coherent light source to create correlated photons. The photons produced by an incoherent light source like an LED are fundamentally uncorrelated.
- dartharva 1y agoI wonder if I will ever see a photonic CPU in my lifetime. Probably not, you'll have to invent a completely new material never seen before that somehow enables nonlinear interactions with light signals. It'd be nothing short of magic.
- cubefox 1y agoThis article is misleading. TSMC doesn't "bet" on the tech by Avicena (the startup in question). Instead, Avicena appears to simply pay TSMC to help them with manufacturing. Here is the linked press release by Avicena: https://www.businesswire.com/news/home/20250422988144/en/Avicena-Works-with-TSMC-to-Enable-PD-Arrays-for-LightBundle-MicroLED-Based-Interconnects https://www.businesswire.com/news/home/20250422988144/en/Avi... Noting also that there have been multiple articles on IEEE Spectrum about this startup in the past, I really hope the journalists don't own the stock or are otherwise biased.
- BardiaPezeshki 1y agoTSMC is developing custom detectors for Avicena on their own dime. They almost never do anything like for start-ups. That is why it is a bet on Avicena. They are nurturing this technology because they think it has real potential. See the TSMC quotes in the article.