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Comment by praveen9920 | Hacker News Reader

Wow. Impressive.

> 25% increase every year

Is there anything like Moore's law for optical cable bandwidth?

Figure 3 in this open-access paper [0] provides historical scaling trends in optical fiber communication (transport) compared to generation and processing. Depending on the time period under study, bandwidth increases at between 20% and 100% per year.

Though the improvement in transistor economics has definitely benefited transport, the large bulk of improvement over time is due to breakthroughs in manufacturing, materials science, semiconductor optics, and signal processing.

[0] https://ieeexplore.ieee.org/document/7839935

Yes. At least a general trend of increasing the demonstrated transmission rates year after year.

In the past five to ten years, there has however been a discussion of wether this can continue and if we hit upon the speculate “capacity crunch“ – aka reaching the operational fiber capacity. This is all considering a single fiber strand.

The limit to the rate through the fiber is not well understood and a quite active research area. Previously, the “limit” has been broken by technology shifts, such as coherent transmission, different amplifier technology, more advanced signal processing. The big question is what the next big shift will be. Combs, as presented in the article are a promising direction.

More so when you work out how much data is inflight, maybe we see fiber reels used as storage/memory. Kinda like what we had in the early days of wire memory. May well see that come back into play with speeds like this for some uses cases.

The speed of light works against you in that case. Even at the incredible 14Thz line rate achieved here, 1km of fibre can have ~146kbits bits in flight at a time.

Yes, though in this instance they pulled of 44terrabits rate per second, so with that you would be looking at 156 megabits inflight over a 1km cable if my napkin maths are correct. Thats 18 megabytes, sure error rate etc and correction would limit that a bit as nothing works as ideal, but sure does seem like may have some uses come into play.

Especially considering how cheap fibers are in comparison to patterned silicon. If the access patterns fit, it might be useful as high-bandwidth memory.

46 megabits at 3.34µs per kilometer[1], however error correction brings that way down. Regardless 1KM of fibre is quite substantial, we're talking densities far lower than even 70s technology. Worse if you try to up the cable length for larger storage latency will increase with it.

1: https://www.m2optics.com/blog/bid/70587/Calculating-Optical-...

Is that an optical fibre delay line?

If you just need a fixed delay in the order of ns, sure. But the fact that it isn't randomly addressable makes me think it won't be useful for anything general purpose.

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