5 ms·
> You might be right and they are talking about fibre bundles The caption of the image of the cable and connector reads: "CMOS ASIC with microLEDs sending data
by topspin 1y ago
> You might be right and they are talking about fibre bundles
The caption of the image of the cable and connector reads: "CMOS ASIC with microLEDs sending data with blue light into a fiberbundle." So yes, fibre bundles.
> I don't see any advantage over vcsel arrays
They claim the following advantages:
1. Low energy use
2. Low "computational overhead"
3. Scalability
All of these at least pass the smell test. LEDs are indeed quite efficient relative to lasers. They cite about an order of magnitude "pJ/bit" advantage for the system over laser based optics, and I presume they're privy to vcsels. When you're trying to wheedle nuclear reactor restarts to run your enormous AI clusters, saving power is nice. The system has a parallel "conductor" design that likely employs high speed parallel CMOS latches, so the "computational overhead" claim could make sense: all you're doing is latching bits to/from PCB traces or IC pins so all the SerDes and multiplexing cost is gone. They claim that it can easily be scaled to more pixels/lines. Sure, I guess: low power makes that easier.
There you are. All pretty simple.
I think there is use case for this outside data centers. We're at the point where copper transmission lines are a real problem for consumers. Fiber can solve the signal integrity problem for such use cases, however--despite several famous runs at it (Thunderbolt, Firewire)--the cost has always precluded widespread adoption outside niche, professional, or high-end applications. Maybe LED based optics can make fiber cost competitive with copper for such applications: one imagines a very small, very low power microLED based transceiver costing only slightly more than a USB connector on each end of such a cable with maybe 4-8 parallel fibers. Just spit-balling here
- deleted 1y ago[deleted]
- nsteel 1y agoAren't they also claiming this is more reliable? I'm told laser reliability is a hurdle for CPO. And given the talk about this as a CPO alternative, I was assuming this was for back plane and connections of a few metres, not components on the same PCB.
- topspin 1y ago> Aren't they also claiming this is more reliable? Indeed they do. I overlooked that. I know little about microLED arrays and their reliability, so I won't guess about how credible this is: LED reliability has a lot of factors. The cables involved will probably be less reliable than conventional laser fiber optics due to the much larger number of fibers that have to be precision assembled. Likely to be more fragile as well. On-site fabricating or repairing such cables likely isn't feasible.
- nsteel 1y agoI understand that CPO reliability concerns are specifically with the laser drivers. It's very expensive to replace your whole chip when one fails. Even if the cables are a concern (I've no idea), having more reliable drivers would still be preferable to less reliable cables, given how much cheaper/easier replacing cables would be (up to a point, of course).
- topspin 1y ago> I understand that CPO reliability concerns are specifically with the laser drivers. Yes. I've replaced my share of dead transceivers, and I suspect the laser drivers were the failure mode of most of them. That doesn't fill in the blank for me though: how reliable are high speed, dense microLEDs?
- nsteel 1y agoAnd are they going to work out any better than Linear Drive Optics, the more obvious alternative?
- topspin 1y agoLDO is just integration. It certainly has value: integration almost always does. So it's clearly the obvious optimization of conventional serial optical communication. This new TSMC work with parallel incoherent optics is altogether distinct. No DSP. No SerDes. Apples and oranges.