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Comment by jpmattia | Hacker News Reader

That jumped out at me too. My wild guess is that the older fiber is a 10G system, the new one is 40G.

From [1] > Unity cable system consists of eight fiber pairs, has design capacity up to 7.68 Tbps, with each fiber pair operating at 96x10G DWDM system.

From [2] > the SJC cable system consists of 6 fiber pairs with the initial design capacity of 28 terabits per second,

Taking a guess that there are 96x40Gb/s x 6 fibers gets you to 23 Tb/s, so in the right ballpark. (Wavelength spacing on a fiber is different between 40G and 10G, so this is a bit of a shot in the dark.)

Caveat: 40G used to be near and dear to my heart (Big Bear Networks), so everything pretty much looks like that nail to my hammer.

[1] http://submarinenetworks.com/systems/trans-pacific/unity [2] http://www.globe.com.ph/press-room/globe-regional-connectivi...

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Nope this will be 100G per wave not 40G. 40G was a stop-gap technology that never really shipped in large volume. With the advent of coherent optical, everyone just went to 100G (eg. Infinera, Ciena, Alcatel-Lucent)

EDIT: One caveat, depending on a particular link many of these systems will run at half-rate. A lot of legacy cables today are running BPSK at 50G in 2 waves (25G/wave) due to nonlinearities.

> Nope this will be 100G per wave not 40G.

Do you have a link for this? Interesting news if true. Also: Things running at 50G used to be OC768 with error correction, ie 40G of data + 10G of overhead. Has this changed? At some point, the framers have to deal with standardized bitstreams, so is the 50G one part of an inverse mux or combined up from 10G?

Edit: It's been a while. Sorry for the bazillion questions, but curiousity is getting the better of me. Are folks really running 100G coherent undersea currently?

See for example: http://newswire.telecomramblings.com/2013/01/telstra-global-...

So you have to separate the "wet" plant from the terminal gear. The speed of the terminal gear is completely disconnected from the wet plant these days. Nobody replaces wet plant to upgrade capacity. They run Ciena, Infinera, Alcatel gear over Tyco's old line system.

Essentially the issue with upgrading over the wet plant is basically the presence of nonlinearities on the fiber. The links are not noise limited. Some of these fibers are still running 10G OOK in half the band and that on NZ-DSF that's used for submarine cables basically causes huge nonlinear penalties. The new subsea fiber is 22ps/nm-km and essentially larger effective diameter for reducing nonlinear penalty.

http://www.corning.com/opticalfiber/products/vascade_fibers....

BTW, I also worked at BBN

> See for example:

Thanks for the link. I confess I'm a little amazed that Infinera is the basis for running 100G coherent single wavelengths. That's great progress. (Edit- See below)

> Essentially the issue with upgrading over the wet plant is basically the presence of nonlinearities on the fiber

Yes, and there's great incentive to utilize legacy fiber if possible.

(BTW I managed to screw up my comment above when I edited. I had written: Usually the undersea guys are a generation behind, partly because of the need to send a destroyer-looking ship out for any repairs.)

> BTW, I also worked at BBN

Hello! and hope all is well, whoever you are. :)

Edit: The infinera 500G PIC in the PR from Telstra is running its basic bitstreams at 25G and muxing them up - http://www.lightreading.com/optical/dwdm/infinera-unleashes-...

Yes. It's a 100G service though. Infinera runs on 25G spacing so at 25G dual wave dual polarization is 100G in the same spectral efficiency as single wave.

Unity! http://www.youtube.com/watch?v=3yLJ5NHARMk

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