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Comment by peeters | Hacker News Reader

> Researchers say they have created fiber cables that can move data at 99.7 percent of the speed of light, all but eliminating the latency plaguing standard fiber technology.

If by "all but eliminating" they mean "reducing by 31%".

There's a hard limit to how low latency can go. We've been close to it for years. So a hop takes 100 ms instead of 150 ms? They're still in the same ballpark. To have a revolutionary impact, it would have to drop the latency an order of magnitude, which, as far as we understand our universe, is impossible.

I guess the real application is over short distances. I'd love to hear the ideal usecase that benefits from this improvement.

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The problem with this technology is that at a 3.5dB/KM loss, it's only really good for about 10KM. At such short distances, the latency difference would only be about 0.0167ms. Given all the other latencies involved between two end-to-end hosts, that's hardly worth laying new fiber for. Unless they manage to reduce the loss to within a reasonably small multiple of more traditional fiber, this new technology isn't going to have much adoption.

At only 37 channels, compared to the 80 that more traditional fiber can carry using DWDM, it also carries less than half the capacity. And that's assuming that it's capable of the same bandwidth capacity per channel; the article states 40Gbps per channel, whereas you can already go as high as 100Gbps over a single wave using DWDM, which means it may only be able to carry 18.5% as much.

Also, I don't see this technology being compatible with erbium-doped fiber amplifiers. See, even the best glass fiber is good only up to 80 km, that's not enough, but by placing a piece of erbium-doped fiber it acts as a laser-amplifier and the fiber lenght can go up to 4000 km. Now that's useful. IMHO the EDFA is the technology that really enabled high-speed internet.

Why couldn't these fibres work with EDFAs? As long as the fibres are designed to operate in the C-band (~1.55 micron wavelength), there shouldn't be a problem running them through an amplifier.

No physicist here but I think there may be losses in the interface air/glass. Also, air contains water and other elements that may present too much attenuation at 1550 nm. I suspect the different lambda is one of the reasons of the limited bandwidth of the hollow fiber. I should try to RTFA.

It's overcoming the losses in the interfacing that's the innovation here - holey fibres have been around for a while. Note that it's the same research lab doing this work as invented the EDFA in the first place.

Is the capacity limit of 37 channels a fundamental limit due to the design, or a consequence of fabricating these fibres in a university lab? I'm honestly asking since I can't access the full text at home, but I suspect it's the latter reason.

This isn't a limit of the lab. They've a full fibre drawing tower and develop new techniques for industrialisation.

Don't underestimate the desire of Wall Street for lower network latency. A 33% reduction in latency is a BIG DEAL when you do high-frequency trading.

OK, say it does. But give it a few years for the technology to propagate, and all traders will have the same latency, eliminating any advantage it once had. So not really revolutionary in the big picture for that case.

"all traders will have the same latency"

Still not the case. The state-of-the-art networking technologies are expensive (300K+/yr per data center plus inter-facility connectivity running into the 1-5M/yr range)

Sure, Finance will be the first to adopt, but it actually has pretty big implications in larger internet use cases.

Lets say your application needs <50ms latency, low enough that your users can't notice. Today, you'll something around 10 datacenters in the USA/Canada to achieve this.

If cut that down by 31%, you might only need 6. (or less, this would take some real math to figure out).

But the impact is pretty large in the long run, if it can really cut long haul latencies by 31%.

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