Record-breaking chip can transmit 1.8 petabits per second

>Using only a single light source, scientists have set a world record by transmitting 1.8 petabits per second.

In 2021 the world record was 300 TB[0]. Why is the headline misleading? for reference, the headline is currently "Record-breaking chip can transmit entire internet's traffic per second." This seems to be correct:

>According to a study from global telecommunications market research and consulting firm TeleGeography, global internet bandwidth has risen by 28% over the course of 2022, with a four-year compound annual growth rate (CAGR) of 29%, and is now standing at 997Tbps (terabits per second).[1]

>Normally, data over a fiber is multiplexed using many wavelengths of light (wave-division multiplexing, or WDM for short). These wavelengths are generated from an array of lasers, forming a frequency comb.

I think that is a relativly new techniuque. For example see https://www.nature.com/articles/s41467-019-14010-7 :

>Optical frequency combs were originally conceived for establishing comparisons between atomic clocks1 and as a tool to synthesize optical frequencies2,3, but they are also becoming an attractive light source for coherent fiber-optical communications, where they can replace the hundreds of lasers used to carry digital data

So "normally" might give the wrong impression. As far as I know, no commercial service is using it. One reason is the cost, which this article addresses by proposing a chip based apporach which makes it cheaper and easier.

[0]https://www.nict.go.jp/en/press/2021/07/12-1.html

[1]https://www.computerweekly.com/news/252524883/New-networking...

Edit: I should point out that the "previous" record was with a 4-core optical fiber, whereas this one uses a 37 core one. They are really two different things: one about the cable and the other about the transmitter. So this one doesn't "beat" the other.

https://www.wolframalpha.com/input?i=1.84Pbps+*+1km+%2F+c

Ping between USA and EU might be what, 100ms round trip? So how much would you think 20x spools of transatlantic fiber plus all the repeaters and power to run it will cost you? And for that you get a memory with O(1s) latency as opposed to DRAM which is 10 million times better latency.

Or you could go with NAND for about twenty thousand dollars for that much storage with only 1 million times better latency. Or HDD at a few thousand and still get 100x better latency.

Maybe my math is wrong, but I'm not quite seeing the niche for this new form of slow billion dollar cache.

In 2004, researchers at UC Berkeley first demonstrated slow light in a semiconductor, with a group velocity 9.6 kilometers per second.[5] Hau and her colleagues later succeeded in stopping light completely, and developed methods by which it can be stopped and later restarted.

https://en.wikipedia.org/wiki/Slow_light

BTW, congrats on your success.

What modulation, bitrate and spectral efficiency did you use per WDM channel?

Was that rate achieved in real-time or with massive post processing?

what's the tx launch power?

what's the frequency bottom end and top end, in nanometers or THz? does this all run in the normal ITU DWDM range from approx. 1528nm up to 1568nm, or wider than that?

https://www.fiberoptics4sale.com/blogs/itu-standards/1004345...

what's the expected path loss? I assume this is some normal 9/125 singlemode fiber and two strands.

what's the usable RSL threshold on the far end?

Next thing you know, you have linux compiled to WASM running a docker container built to host ffmpeg for you.

In the lab, the most common scenario is to have a pseudo-random bit sequence (PRBS), and usually the sequence is 2^31-1 bits long. This makes both the generation (on the transmit side) and error-rate detection (on the receive side) reasonably straightforward, although it can be tricky to read out every one of the receive channels to check the bit-error rate (BER).

Here's typical PRBS BER equipment: https://www.anritsu.com/en-us/test-measurement/products/mp19...

Spoiler alert: The test equipment isn't cheap.

Edit: Probably should mention- PRBS from a linear-feedback shift register is used, because in a PRBS of 2^N-1 you are guaranteed every permutation of N bits long, except for N x zeroes in a row. This measures the wideband system, so if there are spurious resonances in the wide pass band, errors will result.

Lab testing of this scale of transmission involves a bit of “educated simplification”. We had some hundreds of wavelength channels, 37 fiber cores and two polarizations to fill with data. That is not realistic to actually do within our budget, so instead e split the system into components where there is no interference. For example, if there is different data on all neighboring cores compared to the core-under-test, then we dare to assume that the interference is random, without considering neighbors’ neighbor etc.

This reduces our perspective to a single channel under test with known data and then at least one other channel which is just there as “noise” for the other channels. The goal is to make the channel-under-test have a realistic “background noise” from neighboring interference. This secondary signal is sometimes a time-delayed version, sometimes a completely independent (but real) data signal.

This left us with a single signal of 32 GBd (giga symbols / s). This is doable on high-performance signal generators and samplers.

radio telescopes tend to be located in very remote places with very few dedicated dark fiber options.

from the perspective of somebody in the ISP business, go try to buy a 100GbE transport circuit from $random_radio_astronomy_telescope_site to a meet-me room/traffic exchange point at a major internet infrastructure site....

you're going to run into economic problems really quick.

Either way, the bulk of the web is structured to put data as close to where it's needed as possible, to keep things quick and uncongested. So, it doesn't surprise me that internet backbones are much thinner than the aggregate of last mile connections.

The interesting thing about a five alarm fire is that it turns out that it takes about 10 fire trucks to run 5 hoses. The city water system, like the Internet, is designed to deliver a certain amount of volume per day, and to be able to move a reasonable amount of it to arbitrary locations, but not a large fraction of its total capacity to one spot.

A city hydrant can't keep up with multiple fire hoses, even with a pumper truck there to give it enough pressure to go onto the fire. So what you have to do is daisy chain trucks, hooking trucks up to hydrants on separate water mains, or opposite ends of the same loop, then pump that water to another truck that pumps it onto the fire.

You can't overbuild capacity without passing those costs on to customers, so you do what you can to keep the system working smoothly and have workarounds for situations where the abstraction leaks, like a once a decade five alarm fire, or an Internet Hug of Death.

Each of the multiplexed channels are individually limited by the Shannon limit, and with higher power the fiber's Kerr effect creates interference which creates a sweet spot for the optimal optical launch power.

the novelty here is that the spectral channels are all generated from a single laser source rather than a laser per channel

But in very general, you have around 200THz of range for these infrared lasers. So on a single core, I'd expect the max to be within an order of magnitude of 200Tbps. They're using 37 cores, so they're getting 50Tbps per core right now.

Order of magnitude because it's not super hard to approach a bit per Hz of bandwidth from the bottom side, though difficult at very high frequencies, while it gets exponentially hard to exceed it. And here's a couple relevant charts for how fiber is extra self-limiting: https://i.stack.imgur.com/bwTy2.png http://opticalcloudinfra.com/wp-content/uploads/2017/07/Nonl...

Not sure what the baud rate of a single channel was in their experiment but probably between 32-80Gb which is common for the lab equipment at Universities. The industry is knocking on 100-400Gb where for the actual decoding and signal processing there is massive parallelism applied to reduce the rate even more

In an experiment like this, only the initial light source is modulated and therefore all channels carry the same data. The equipment for the transmitter and receiver chain is so expensive that university labs can barely afford one of each.

It's poorly worded, sure, I'll give you that. But anyone should be able to understand that what they meant was "The internet on average transfers a certain amount of data per second, and this chip is capable of transferring at that rate."