1.53 Petabits per Second Transmission in 55-Mode Fiber

https://www.nict.go.jp/en/press/2022/11/10-1.html

by geox • 4 years ago

85 30 4 years ago

nict.go.jp

rowanG077• 4 years ago

Insane. I wonder how you would even design a memory subsystem for this. Back of the envelope calculation says you'd need at least a 212500 bit wide DDR5-7200 bus to even approach that throughput.

wbl• 4 years ago

My guess is that it gets treated as 55 separate optical channels each with their own receivers and that there is considerable multiplexing on top.

krisroadruck4• 4 years ago

These things don't go to a single system. The signal is optically split at the ends and there are big racks of transceivers, each transceiver deals with a single mode. With 55 modes you are looking at dealing with 27 terabits or 125 terabytes per second on any given system.

MayeulC• 4 years ago

I get 28.5 Tib/s, so 3.6 TiB/s, not sure how you went from 27 to 125?

nine_k• 4 years ago

I suppose this is not about larger bandwidth from/into one system, but about fewer long cables (say, transoceanic).

krisroadruck4• 4 years ago

Oh wow. No guarantees, but they mentioned they achieved this on a single wavelength, and that wavelength multiplexing should be possible. Current Dense Wavelength Division Multiplexing (DWDM) supports something like 160 channels. If they are able to combine both of these technologies - theoretically you are looking at nearly 250 Petabits per second on a single fiber strand.

Thing is, no one is pulling a single fiber cable. Modern fiber cables can contain up to a thousand fiber strands in a single cable although the highest strand-count single-mode fiber cable commonly manufactured is the 864-count, consisting of 36 ribbons each containing 24 strands of fiber. Even oceanic cables frequently have 48 or 96 fibers.

That means, again theoretically, a land based 864-core cable can carry over 200 exabits per second, and an oceanic 96-core can carry 23.5 exabits per second. That's bananas.

Edit:

Very large numbers are hard for humans to grok. Some context on 200 exabits - There are 335,591,597 people in the United states. If you were to divide the bandwidth evenly between all those people, each person would have approximately a 600 gigabit connection. An UHD Blu-ray (4K, HDR) movie is about 50GB. On this connection you could transfer that in under 1 second (hand waving away overhead, write limitations and connection/handshake delays).

shalmanese• 4 years ago

That means, again theoretically, a land based 864-core cable can carry over 200 exabits per second, and an oceanic 96-core can carry 23.5 exabits per second. That's bananas.

The total amount of data generated per day is estimated to be 97 zetabytes [0] which is only 9 exabits per second. You could run the entire internet off a single cable that winds its way around to every single person and they could just siphon off the data they need.

[0] https://www.statista.com/statistics/871513/worldwide-data-cr...

gpderetta• 4 years ago

Next question is, how long does the cable need to be to store the content of the entire internet and get rid of any other storage?

taldo2• 4 years ago

Subsea cables usually have 4 or so fibers, since they need repeaters every so many km, which drives the cost-per-fiber (the actual strand of glass is approximately free for all practical purposes).

krisroadruck4• 4 years ago

This may have been true in the past but new subsea cables are not this limited. As an example the Dunant transatlantic long haul Google put in place in 2018 (went live in 2020) has 12 pairs (24 fibers). Grace Hopper, due online this year has 32 fibers. But your point stands - I should have said "up to" instead of "frequently".

dale_glass• 4 years ago

While this is really neat, is it actually much of a problem?

I mean, fiber is cheap and you can put many strands into a not particularly thick cable, and there's DWDM as another comment says.

Is actually running into the limits of the fiber a frequent occurrence anywhere in the industry, like in the submarine cables?

tyingq• 4 years ago

Assuming it works on existing fiber, just more bandwidth without new install costs.

Supposedly• 4 years ago

How are we going to encrypt that?

LinuxBender• 4 years ago

I believe scaling is accomplished in this case by having each node handle encryption. The fiber transport itself need not encrypt the payload. There are cases where businesses encrypt their leased dark fiber for compliance reasons so their limit would be whatever their VPN routers/appliances can handle at the time.

MadameBanaan• 4 years ago

As a photonics engineer, I'm more impressed by the 55-mode fibre than anything else

namibj• 4 years ago

I'm not an engineer when it comes to photonics, just curious, and I didn't even know this would be stable enough to work with.

dmix• 4 years ago

Can you explain what that means to someone not deeply familiar with networking?

Vt71fcAqt7• 4 years ago

Can you explain what multi-mode fibres are? From what I've read, it allows for WDM over a single fibre. But what is physically different about these multimode fibres that allow for this Space-division multiplexing? Wikipedia says:

Multi-mode fiber has a fairly large core diameter that enables multiple light modes to be propagated and limits the maximum length of a transmission link because of modal dispersion.[0]

But that's clearly wrong because here we are using the standard diameter.

[0]https://en.wikipedia.org/wiki/Multi-mode_optical_fiber

visarga• 4 years ago

If only CPUs could get data from memory at these speeds.

hinkley• 4 years ago

In a similar article we discussed a ring structure to store data. You could store about an L1 cache’s worth of data in a loop that’s roughly a nanosecond long.

Problem we didn’t discuss is this: L1 cache is less than 1/3ns on high end hardware, meaning that L1 caches currently have about 1/3 the latency of this light loop.

Once this doubles or triples again you might have a solution for L2 cache though, since chip clock cycles are relatively stuck.

aborsy• 4 years ago

These scientists create these impressive hardware systems, important to technologies that we use. Yet, there aren’t all that many jobs in US in hardware and manufacturing sectors, and they don’t pay well either (far less than software engineers with a lot less investment in expertise). The system is not fair.

nullc• 4 years ago

Is the mode structure of an installed cable stable enough for this? or are the 55 subchannels going to get scrambled up every time the wind blows the cable?

mike503• 4 years ago

And on Comcast it still somehow maxes out at a 35 Mbps upload

1.53 Petabits per Second Transmission in 55-Mode Fiber

Related Stories