Novel hollow-core optical fiber transmits data faster with record low loss | Hacker News Reader

Novel hollow-core optical fiber transmits data faster with record low loss

phys.org

136 pointsWingy65 comments

Note here that "faster" here really means more speed and not an increase in the volume of data transferred : The light go through the air hollow-core so can go at near "c" (the speed of light in vacuum) speed, instead of being constrained to "speed of light in glass which is only "2/3 c". This allows reduce latency for long distance communication.

https://spie.org/news/photonics-focus/julyaug-2022/speeding-...

So submarine cables were limited to 0.67c and now aren’t? Can this really work?

> So submarine cables were limited to 0.67c and now aren’t?

I think it’s more like in the future they might not be. It’s anyone’s guess how mass production and deployment of this might look.

For submarine cables there are two things here. The first is lower attenuation which allows for fewer amplifiers along the route making it overall cheaper. The second is lower latency. There have been cases where high frequency trading people went wireless to get lower latency because of the higher propagation speed of EM-waves in air. For really long distances you can go theoretically use satellite links to get lower latency than a submarine cable even if the total distance increases.

Someday, someone is finally going to work out how to do comms with neutrinos (which can pass directly through the Earth and come out the other side) and make so much money...

They are not, for the thing that would make neutrinos useful for communications is also the thing that makes them useless for communications. In order to use them for comms you'd need to produce such a huge number of neutrinos, and/or in a very colimated beam, that one shudders to think of how one might produce them!

I suspect it may be possible using neutrino-antineutrino annihilation if there's a good way to produce streams of both types of particles, but... physics isn't my field.

I think you could moderate a large nuclear fission reactor (on the edge of criticality) to produce detectable differences in neutrino rate on the other side of the world. KamLAND and a few other experiments detected multi-GW reactor anti neutrinos at 1000km[0] and so presumably tens of GW (easily [if perhaps not safely?] achievable briefly in current reactors) should be detectable over 8000km.

[0] https://www.sciencedirect.com/science/article/pii/S173857331...

It's true, but for most cases, the volume of a fiber is not the problem anyway. Latency is a problem most of us somehow bump into every day, while most fibers in the ground are nowhere near what you can push out of DWDM (e.g., off-the-shelf equipment will easily allow you to run 20x100Gbit over a single fibre, but many of them only carry a single 10Gbit or even 1Gbit link).

Trans-continental is different, because you'll need amplifiers. Many, many amplifiers in a row. And those generally work well only in a fairly limited band. But unless you're doing submarine, bandwidth is almost never the problem.

To make things worse, a lot of existing medium-haul fiber links are actually twice as long as you'd expect, due to the desire to cancel out dispersion; you first run the fiber e.g. 10km from place to place, and then run it through a large 10km spool (of a slightly different type of fiber) in the datacenter to cancel out the dispersion. This is slowly going away, but only slowly.

does using hollow core means you can do away with dispersion compensation?

AFAIK yes, but if that's your goal, a far easier solution is to just use transmission standards that don't care about dispersion (coherent detection). E.g., all 100gig transmission already does not care about it.

Sounds like it was something like CML for >200km runs. =3

>To make things worse, a lot of existing medium-haul fiber links are actually twice as long as you'd expect, due to the desire to cancel out dispersion; you first run the fiber e.g. 10km from place to place, and then run it through a large 10km spool (of a slightly different type of fiber) in the datacenter to cancel out the dispersion. This is slowly going away, but only slowly.

Only slowly? I haven't worked with very long haul wdm systems or sonet/sdh but I've never seen this. Maybe you mean much longer distances than 10km as we've had 10G-LR for ages that don't need this.

I don't know exactly how long gives you too much dispersion (obviously depends on the fiber), but if it's short enough you just don't need to care, indeed.

I don't work with this myself, but my understanding is that you only start ripping this out when you are positive every wavelength from every customer actually has coherent detection, and that could take a while. :-) Obviously this will differ from site to site, too; I would assume new ones don't care unless there's a lot of legacy involved.

Alien wdm isn't common in long haul systems though, if so the provider typically provides the transponder. Usually customers use regular grey (1310nm 10G-LR) to the provider and the provider turns that into something compatible with their dwdm system.

Huh, interesting, I didn't know this was a thing at all. But you still need to make sure you don't have a stupid customer sending 1000baseLX with direct detection in the other side for this to work. :-)

Newer coherent optical transceivers don't need physical dispersion compensation as they just do it in digital signal processing instead. That is the magic of ever increasing rates of computation at lower power expenditure.

Thus going away (see my other comment in the same subthread).

Thanks for your precision. Off-topic: It's true that "faster Internet" means "bigger Internet" in common language, just like in photography "faster lens" means "lens with more light gathering capability". I wonder if there's other field where "faster" is misused.

Higher bandwidth means less time to transmit a given packet. Just like more light gathering in a lens allows faster shutter speeds.

If you had to move 100 tons of packages, which is going to be faster - a Lamborghini going 200 mph, or a tractor/trailer going 50mph?

If you’re trying to set a speed record and don’t care about bringing anything along, which is faster?

Neither meaning is necessarily wrong.

Even if directly it isn't technically right to say it's faster, but with it's applications built upon such technology it manifests in these tasks being done faster. Makes sense.

And the time for the lambo and the tractor will depend on the round trips each will have to do, so it depends on the medium.

This is actually much more important than the volume of data transferred. Having 33% lower latencies across the globe would be huge.

On the other hand, it is only 33% - and that is an upper bound.

Getting data to literally the other side of the globe currently takes about 100 milliseconds. How many truly novel applications open up by that latency dropping to 66ms?

For short-distance stuff the latency is already low enough to be practically realtime. For long-distance stuff we're already fast enough for human-level applications (like video chat), but it's not dropping enough for computer-level applications (like synchronous database replication).

I'm sure some HFT traders are going to make an absolute fortune, but I doubt it'll have a huge impact for most other people.

I generally agree with you, but! Video or audio calls between EU and the US still have a much higher chance of speaking up at the same time and it’s due to lag. If the latency is decreased by 33% it might be a game changer.

I made my master thesis on real-time, with a chapter where I experimented with different levels of jitter and latency. Jitter is the consistency of the latency, is it like a locked 66ms or sometimes does it go to 200ms. Jitter is more impactful than latency for a wide range of applications, from gaming to music and video call. Having a lower latency allows for lower jitter, or less jitter while keeping the same latency. Today’s discovery is huge imo.

Doesn't jitter come from the switches and routers along the path? I have a hard time seeing a fibre having significant jitter.

Also, there is a very narrow threshold of latency timings in which "real time" communication goes from looking real time to actually feeling real time. That narrow window is why people end up interrupting each other or feeling like they can't get a word in edge wise on video calls all the time.

Great for gamers

HFT traders probably won't make any extra money unless they deploy this first to their dedicated international links.

Almost all of them deploy their strategies within exchange colo's already

There's a lot of need for communication still. In US, futures trade mostly in Chicago, but equities in New York, for example. In Europe things trade all over the place.

HFT uses microwaves for anything over distance. Unless this beats microwave latency, this doesn’t do anything for them fwiw

Microwave is only feasible over medium distances - can't do it over the ocean, as it requires LoS. Also IIRC, microwave bandwidth is considerably lower than fibre, and sometimes it matters.

Microwave is also affected by weather. They sometimes say that markets are slightly less efficient on rainy days. It’s a bit of a joke, but basically packet loss goes way up and they rely more on fiber links when microwave links are being shitty.

You still need to traverse physical segments in the wireless path: think receiving dish to the next transmitting dish, the end of the path to get from the trading systems onto the roof and into to the first dish, etc. Every nanosecond counts.

Traders have at least experimented with shortwave too: https://spectrum.ieee.org/wall-street-tries-shortwave-radio-...

> I'm sure some HFT traders are going to make an absolute fortune, but I doubt it'll have a huge impact for most other people.

They’ve been using hollow core fiber (and funding research into it) for nearly a decade. I know it goes back further than the 2017 spinoff mentioned in the article, but https://optics.org/news/11/9/52 talks about it a bit.

> and that is an upper bound

I've often wondered if for HFT or similar it might be worth pointing a particle accelerator at the floor and going for direct-line transit times. I'm fairly sure that this is theoretically possible, but no idea if the engineering challenge is beyond reach for use as a communication link.

If your signal is "transparent" enough go through so much rock and iron without being absorbed (like neutrinos), you'll have a hard time capturing it on the receiver side.

Well, OPERA was 700ish km, but had Cern at one end. If one has this as the sole goal and wanted to do it real-time over 12,000km is it "engineering-possible" vs "theoretically-possible" ? My guess is that it depends how much money stands to be made ;)

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

Basically just aim you accelerator at any neutron detector.

Problem is you'd drop more packets than IP over pigeons.

I think you're confusing neutrons and neutrinos. Firing neutrons at the floor will definitely give you a very radioactive floor.

Does carrier pigeons have that high packet loss?

online music playing is HEAVILY latency sensitive. (for instance an online jazz session)

then you have online video games. increasing the area where you can get good connections increase quadratically (or more, if we hit step function = big city get in range) the viability of niche multiplayer video games and it is thus a boost to creativity.

there are probably many more niches... (need to think of reachable area, quadratic, instead of 1-to-1 link linear)

Mind-boggling logic, for example any existing roundtrip-heavy application (such as CIFS) would gain visibly and immensely because that latency is multiplicative

What this would do is increase the radius of where you can do some latency constrained thing. If your latency budget is 20ms, you could now do that over a bigger areas.

don't know about truly novel, but CS:GO players certainly would benefit.

Interesting quotes from the article:

"There has not been a significant improvement in the minimum attenuation—a measure of the loss of optical power per kilometer traveled—of optical fibers in around 40 years...

"The new design maintains low losses of around 0.2 dB/km over a 66 THz bandwidth and boasts 45% faster transmission speeds...

"The new fiber is a kind of nested antiresonant nodeless hollow core fiber (DNANF) with a core of air surrounded by a meticulously engineered glass microstructure.

"The team believes that further research can reduce losses even more, possibly down to 0.01 dB/km, and also help to tune the fiber for low-loss operation at different wavelengths. Even the losses achieved, however, open up the potential for longer unamplified spans in undersea and terrestrial cables and high-power laser delivery and sensing applications, among others."

> "The new design maintains low losses of around 0.2 dB/km over a 66 THz bandwidth and boasts 45% faster transmission speeds...

0.2 dB/km is already a pretty common loss ratio, though. It's true that you won't get that over the entire 1310–1550nm range (the ~35 THz range commonly in use), but you generally can't use all of that for long-haul links anyway due to the way repeaters work.

More interestingly, they promise 0.06 dB/km or so in the most relevant bands. If they can keep that up, it would mean less need for amplifiers, which is a Good Thing(TM).

This could be a big deal for multiplayer gaming. Right now there is enough margin in splitting east/west regions in latency sensitive games. With HCF, the argument for talking to one central region starts to prevail. For a game like counter strike with client-server, you don't actually need to go coast to coast. The server is the authority. If everyone can talk to Dallas or Ohio in <50ms they're probably going to have an OK time.

I really didn't see this coming. After 40 years of fibre I just thought we should roll this out across the globe as the solution to every home and we had data transmission solved and likely wouldn't need an upgrade until we found something substantially better, maybe quantum entanglement communication. Turns out it was improvable and now the insane amounts of fibre we have already deployed is now obsolete.

The currently installed fibre cables work just as well as they did a year ago. Calling them obsolete is a bit of stretch.

Besides, I think most homes are not even close to using the full capability of what fibre can offer nor do a lot of people need that extra bit of speed to browse Instagram/Facebook/YouTube/Whatever else.

An old computer and processor work just as well as they did when made but they are still obsolete because something better has been released. This does make all the fibre obsolete, doesn't make it useless but the replacement will reduce latency.

That’s not how it works.

A hammer is not more obsolete for driving a nail because pneumatic nail guns exist.

Using just a hammer on a commercial framing job is silly, however, because pneumatic nail guns work better. Everyone still has a hammer ready though, because it is still needed.

Using a pneumatic nail gun to hang a picture is silly, because it is so overkill (and expensive) that it actively makes it harder to do the job.

This tech doesn’t obsolete existing fiber for last mile because the extra cost associated with producing and splicing it dwarfs any potential gains (which would likely be in the 10’s of ns).

If it is proven to work well, this may obsolete existing transoceanic/transcontinental fiber runs, where the latency difference will be noticeable enough the cost is worth it. However, it’s highly unlikely that anyone will actually turn down any of these existing lines. The different is not so much that the old lines are useless.

If, eventually, this new fiber is at the same price point and as easy to work with as the current fiber? then the current fiber will be obsolete.

The fiber ran right now is nowhere near reaching it’s theoretical usage. The issue is now, and always has been, having someone actually run it. That costs money. It’s also a bit more physically vulnerable, and requires some more care to not destroy, which makes the actually running it part a bit more expensive than copper in many circumstances.

This won’t change anything for 99% of new fiber deployments, and practically doesn’t make any difference for existing fiber deployments either. The actual media is still 100x more capable than anyone’s end termination equipment outside of a lab.

The improvements here are likely irrelevant for last mile. If hollow core fully replaces solid core, last mile deployments would use it, but saving 33% of latency in a fiber that's almost certainly less than 5 ms long isn't cost effective if there is any economic cost. The reduction in loss also doesn't provide a benefit for short runs. If there's an improvement in splicing, that might be useful for last mile, if splicing is harder, then it's less likely to be adopted.

On medium and long distance runs, it will provide a lot of benefits. Reducing latency on a cross country link is palpable; reducing latency on a shorter link like LA to SF is valuable too, because some routes have many of those. Reducing the number of amplifiers needed will be apprechiated by cable operators as well, fewer points of failure, likely a lower power budget, etc.

It may obsolete existing long haul fiber. But installed fiber will still be useful even if there's better fiber that could be installed... And existing fiber will be useful for redundancy and additional capacity even if there's better fiber on the same route.

How does one splice a cable with such a complex geometry? Is that a solved problem already?

You probbaly need a specialised crew to do this and as such such fiber won't be installed in your own neighbourhood for your Fiber-to-the-Home connection anytime soon I guess. But, maybe in a few decades it will.

When such technology becomes practical for the large telco's it will be implemented soon as this saves on attenuation equipment.

The termination/splicing of HCF would likely occur at long haul endpoints, not in neighborhoods and last mile. There wouldn't be any meaningful upside to this. Crews are currently splicing fibers reliably in <5 minutes using gear from Amazon or AliExpress. We don't want to mess with something that is working this well.

I can say from direct experience doing research with hollow-core fibres that they are not easy to splice either to each other or to standard fibre. Imagine trying to use heat to melt together a pipe and a solid cylinder without creating a mess.

Below are some great videos on the physics and practicalities of single mode fiber. They are Thorlabs videos, so are slanted more towards the use of SMF in a laser lab rather than a telecom setting. They reference a lot of the theory, but also provide a good intuition about how and why SMF works so well.

https://youtu.be/FbOXRuBQt_U

https://youtu.be/HvJeXakc8Kc

HCF came up in the recent IEEE Hot Interconnect Microsoft talked a few min about deploying in their HPC datacenters for AI latency reduction important to All Reduce/Gather operations typically in rings that need to converge and where slowest process dictates the pace

https://youtu.be/vuo6KfdRRZw&t=479

UK, so what's the betting no one got a patent on this?!

Skin effect in fiber?!

All the hedge funds sniping orders right now lol

Low latency starlink orders on hold

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