How undersea cable design capacities are calculated

interesting, WACS is quadruple the theoretical speed of SEACOM.

4 x 128 x 10 = 5.12 Tbps
2 x 64 x 10 = 1.28 Terabits

Interesting also if SEACOM upgraded to 40gbps, it would be the same speed as WACS

2 x 64 x 40 = 5.12Tbps

I wonder what the cost if of upgrading? and if its just the main fibre router at the end, or if they need to replace alot more equipment. maybe its just a firmware update?
 
Great article. Thanks Jan for really doing your homework, and presenting a well written article.

I finally understand how design capacity is calculated on submarine cables, and what this 40G technology actually means.

If I understand correctly, then SEACOM is running at 10Gbps per wavelenth x 64 wavelengths x 2 fibre pairs = 1280Gbps = 1.28Tbps. So if SEACOM were to use this new 40G technology, there could theoretically quadruple their capacity, to 5.120 Tbps.

And WACS is running at 10Gbps per wavelength x 128 wavelengths x 4 fibre pairs = 5.12Tbps. If WACS were to use the new 40G technology, they could also theoretically quadruple the design capacity of the cable to 20.48Tbps.

One question though, if the new leg from Portugal to London on WACS is to also run at 5.12Tbps like the rest of the cable, but is using 40G technology, then it means that this leg of the cable is either:
- using only 2 fibre pairs, compared to 4 on the main WACS leg, or
- using fewer wavelengths per pair than the 128 on the main WACS leg, or
- some combination of the above

One of the above values has to be lower on the Portugal to London leg, when compared to the rest of the cable. Otherwise they wouldn't need to use 40G technology to bring the capacity on this leg in line with the rest of the cable's 5.12Tbps capacity.

I guess this also means that WACS can't exceed 5.12Tbps, as the Portugal to London leg is already using 40G technology. They'd have to come up with something like 80G. Otherwise the main leg will run at 20.48Tbps using 40G, while the Portugal to London leg will still be at 5.12Tbps as it will be already running at 40G.

Right?
 
Last edited:
@saajid

I would assume that they will get some more traffic in southern europe to travel to UK. This would mean that if they didnt upgrade this speed, it would bottleneck in Portugal.

Didnt you just repeat the previous two comments?
 
midkemia said:
I wonder what the cost if of upgrading? and if its just the main fibre router at the end, or if they need to replace alot more equipment. maybe its just a firmware update?
Click to expand...

The costs are high. Fortunately with EDFAs nothing has to be done to the cable itself. The higher the bitrate the higher the interface costs. Keep in mind that a cable does not simply have two end points, there are all the landing stations with equipement (add-drop muxes etc) that sit in that cable path that need upgrading. Simply upgrading the DWDM kit with new interface cards etc is not the end of it, the DWDM kit connects to SDH kit which in turn would require new interface cards for the added wave lengths on the DWDM system or upgraded ones if they can't handle 40Gb/s for example. A single wavelength transponder card in a DWDM system could cost hundreds of thousands of rands, now multiply that a few times and add all additional equipment and things start to get very pricey. Telecoms kit is not cheap, it's designed for reliability & redundancy with 99.999% uptime and you pay for that, in comparison other electronics are cheap.
 
Last edited:
Knersus said:
Nice technical article. Would love to see more of these on MBB. :-)
Click to expand...

If you understand the terminology and you can multiply then it's not really technical.

Any suggestions for topics you would like to see covered/explained? Lot's of people on MyBB that could probably write them but then again knowing technical people they hate writing documentation :D
 
That's an incredible amount of bandwidth, what's more incredible is how crap are internet remains. I have a 4mb line syncs at 1.7mb, still can't watch youtube videos without buffering, torrents download between 8kb/s to 25kb/s during the day, sometimes I experience 60kb/s late at night if good seeding. Maximum I have downloaded is 60GB in a month, I think not to excessive compared to others. Way to go Mweb, great having uncapped - yawn.
 
Many thanks for this article - I found it very interesting and informative.

Regarding possible future articles I would like to know the technical motivation and implementation of the asymmetry of ADSL.
 
ponder said:
If you understand the terminology and you can multiply then it's not really technical.

Any suggestions for topics you would like to see covered/explained? Lot's of people on MyBB that could probably write them but then again knowing technical people they hate writing documentation :D
Click to expand...

I'm curios about the last mile and how our connections goes from the home, to our actual ISP. I pretty much get that from my house it goes over copper to the nearest Telkom exchange.. from there it seems like a black hole to me until it finally somehow gets to who ever my ISP is, and from there I get the international line, etc. But the bit between me and the ISP is what I wonder about.
 
Also keep in mind, with using one wave lenght at stm 16 [10Gig] you need a regen [repeater] every 200km [about]
Moving up to 40Gig, your repeater must come closer to each other.

So if the cable runs in the sea, and a repeater every 200 kms you cannot jump to 40gig , you need more repeaters.
 
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X