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TSMC bets on unorthodox optical tech

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Re: TSMC bets on unorthodox optical tech

#101

Post by nsteel »

topspin wrote: post #95
nsteel wrote: post #92

Earlier quoted context omitted.

And are they going to work out any better than Linear Drive Optics, the more obvious alternative?

LDO 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.

Ok, but I'm just after solutions to problems I have talking to other chips. I don't mind what's novel and what's optimisation. Whatever is adopted, in either case it's a step-change from the past 20 years of essentially just copper and regular serdes in this space.

And I'm not sure how much of this is actually TSMC's work, the title is misleading.

Edit: actually, they are working on the detector side.

Re: TSMC bets on unorthodox optical tech

#102

Post by adrian_b »

cycomanic wrote: post #33

That 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-…

The article mentions lengths of up to 10 m, so this technology is restricted to links inside a cabinet or between closely located cabinets.

The claimed advantage is a very high aggregate throughput and much less energy per bit than with either copper links or traditional laser-based optical links.

For greater distances, lasers cannot be replaced by anything else.

Re: TSMC bets on unorthodox optical tech

#103

Post by topspin »

BardiaPezeshki wrote: post #98
topspin wrote: post #74

Earlier quoted context omitted.

> 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 a…

we use borosilicate fibers that are used for illumination applications. You might have seen a bundle in a microscope light for example. And they are incredibly robust compared to single mode fibers. Note the very tight bend angle in the picture - that's a 3mm bend radius. Imagine doing that with a single mode fiber!

> And they are incredibly robust

See my other comment about non-datacenter applications. There is a serious opportunity here for fixing signal integrity problems with contemporary high bandwidth peripherals. Copper USB et al. are no good and in desperate need of a better medium.

Re: TSMC bets on unorthodox optical tech

#104

Post by throwaway48476 »

BardiaPezeshki wrote: post #96
cycomanic wrote: post #33

That 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-…

In datacenters people use optics for longer distances (10m to 2km). Within a rack it is almost always copper. The reason is that for short distances lasers are too expensive, unreliable, and consume too much power. We think microLED based links might replace copper at short distances (sub 10m). MicroLEDs into relatively thick fiber cores (50um) are much easier to package than standard single mode laser based optics.…

So, toslink?

Re: TSMC bets on unorthodox optical tech

#105

Post by LargoLasskhyfv »

BardiaPezeshki wrote: post #96
cycomanic wrote: post #33

That 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-…

In datacenters people use optics for longer distances (10m to 2km). Within a rack it is almost always copper. The reason is that for short distances lasers are too expensive, unreliable, and consume too much power. We think microLED based links might replace copper at short distances (sub 10m). MicroLEDs into relatively thick fiber cores (50um) are much easier to package than standard single mode laser based optics.…

So has Gb/s a new meaning now? Giga blinks per second?

Re: TSMC bets on unorthodox optical tech

#106

Post by mmmBacon »

BardiaPezeshki wrote: post #96
cycomanic wrote: post #33

That 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-…

In datacenters people use optics for longer distances (10m to 2km). Within a rack it is almost always copper. The reason is that for short distances lasers are too expensive, unreliable, and consume too much power. We think microLED based links might replace copper at short distances (sub 10m). MicroLEDs into relatively thick fiber cores (50um) are much easier to package than standard single mode laser based optics.…

It’s not correct to say that lasers are unreliable. Last year more than 20M transceivers shipped. Your statement is not at all supported by real field failure data.

The reliability of micro LEDs. and specifically GaN based micro LEDs is however an open question.

In the absence of any dislocation failure mechanisms it will depend on the current density and thermal dissipation. And just like any other material, it will have to survive in a non-hermetic environment and in the presence of corrosive gasses (an issue in data centers).

To get the 10G, it’s probably kind of like a VCSEL without the grating and so current density is probably high. How well you’re able to heat sink it is going to determine how reliable it will be.

Overall I like the idea. It looks like the beachfront could work. I’d spend more time talking about and how the electrical connection works and what kind of interface to a chip would be needed.

I’d also be careful before throwing shade on laser reliability because it could backfire on you (for all reasons above).

Re: TSMC bets on unorthodox optical tech

#107

Post by morphle »

BardiaPezeshki wrote: post #97
cycomanic wrote: post #67

Earlier quoted context omitted.

You might be right and they are talking about fibre bundles, but that that's something different to a multicore fibre (and much larger as well, which could pose significant problems especially if we are talking cm links). What isn't addressed is that leds are quite spatially incoherent and beam divergence is strong, so the fibres they must use are pretty large, coupling via just a connector might not be easy especial…

The fiber cables we use are basically 2D arrays of 50um thick fibers that match the LED and detector arrays. We've made connectors and demonstrated very low crosstalk between the fibers. Advantage over VCSELs is much lower power consumption overall, much lower cost (LEDs are dirt cheap and extremely high yield), because we are blue light, the detector arrays are much easier and can be modified camera technology, and…

This might be the breakthrough we also have been working on [1] for over 20 years. It would be even better if Avicena wouldn't drive the led array and detector array with high power 10 Gbps SerDes. Even better if you align a blue led array with lenses to a detector array on a second chip: free space optics [2].

I would love to join you at Avicena and work on your breakthrough instead of just acquiring the IP from you in a few years.

[1] https://youtu.be/wDhnjEQyuDk?t=1569

[2] see schematic on page 373 of https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=780...

Re: TSMC bets on unorthodox optical tech

#108

Post by cycomanic »

BardiaPezeshki wrote: post #97
cycomanic wrote: post #67

Earlier quoted context omitted.

You might be right and they are talking about fibre bundles, but that that's something different to a multicore fibre (and much larger as well, which could pose significant problems especially if we are talking cm links). What isn't addressed is that leds are quite spatially incoherent and beam divergence is strong, so the fibres they must use are pretty large, coupling via just a connector might not be easy especial…

The fiber cables we use are basically 2D arrays of 50um thick fibers that match the LED and detector arrays. We've made connectors and demonstrated very low crosstalk between the fibers. Advantage over VCSELs is much lower power consumption overall, much lower cost (LEDs are dirt cheap and extremely high yield), because we are blue light, the detector arrays are much easier and can be modified camera technology, and…

Just wanted to clarify that I don't necessarily doubt that you have a use case (BTW partnering up with someone like intel or so on for optical thunderbold or similar like someone else mentioned would be very interesting as well), you definitely have people who know what they are doing. I thought the ieee article however does give the wrong impressions as it mainly compares with the wrong thing, somebody here (maybe you?) was also saying 50 mu m fibres are much easier to couple into than SMF, which is correct, but also not relevant because VCSEL links typically use OM fibre with 50-60 mu m core diameters as well.

Re: TSMC bets on unorthodox optical tech

#109

Post by maxpotatohead »

mmmBacon wrote: post #106
BardiaPezeshki wrote: post #96

Earlier quoted context omitted.

In datacenters people use optics for longer distances (10m to 2km). Within a rack it is almost always copper. The reason is that for short distances lasers are too expensive, unreliable, and consume too much power. We think microLED based links might replace copper at short distances (sub 10m). MicroLEDs into relatively thick fiber cores (50um) are much easier to package than standard single mode laser based optics.…

It’s not correct to say that lasers are unreliable. Last year more than 20M transceivers shipped. Your statement is not at all supported by real field failure data. The reliability of micro LEDs. and specifically GaN based micro LEDs is however an open question. In the absence of any dislocation failure mechanisms it will depend on the current density and thermal dissipation. And just like any other material, it will…

Haha, given that he is the founder of Kaiam and Santur I think he has the credentials to throw shade.

Re: TSMC bets on unorthodox optical tech

#110

Post by mmmBacon »

maxpotatohead wrote: post #109
mmmBacon wrote: post #106

Earlier quoted context omitted.

It’s not correct to say that lasers are unreliable. Last year more than 20M transceivers shipped. Your statement is not at all supported by real field failure data. The reliability of micro LEDs. and specifically GaN based micro LEDs is however an open question. In the absence of any dislocation failure mechanisms it will depend on the current density and thermal dissipation. And just like any other material, it will…

Haha, given that he is the founder of Kaiam and Santur I think he has the credentials to throw shade.

You made an account just to respond?

Generally it’s a good idea to sell what’s good about your product and not say things that are not true about other peoples products.

Also I wouldn’t brag about Kaiam.

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