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Some more technical details @ https://www.2africacable.com/ https://www.2africacable.com/: > go live in 2023/4 > design capacity of up to 180Tbps on key parts

Some more technical details @ https://www.2africacable.com/ https://www.2africacable.com/: > go live in 2023/4 > design capacity of up to 180Tbps on key parts of the system > 16 fibre pairs > Cable burial depth has also been increased by 50% Patners: * China Mobile * Facebook * Orange * STC * telecomegypt * Vodafone * WIOCC

jeffbee 6y ago
Interesting in terms of scale. That's only about twice the capacity of the fiber connecting California and the almost negligibly-populated nation of Chile. On a per-capita basis Africa needs a lot of cables to Asia and Europe to gain parity.
- nine_k 6y ago
  But past the thin mountainous band of Chile lay large,populous, and reasonably advanced nations of Brazil and Argentina. Likely they share some of the bandwidth.
- ejanus 6y ago
  Google [1] is building one too but for their internal use. [1] https://businesstech.co.za/news/broadband/326323/google-is-building-a-super-fast-subsea-cable-between-portugal-and-south-africa/ https://businesstech.co.za/news/broadband/326323/google-is-b...
- teruakohatu 6y ago
  For comparison the main internet cable connecting my country, New Zealand, to the USA as 10 tb capacity and the cable connecting us to Australia has around 20 tb, so we have a theoretical maximum of 30 tb of overseas capacity for 4.8 million people (in practice Australian traffic will also be routed over our USA cable). We should have an additional 70+ tb by the end of 2022 after cable upgrades (again, shared with Australia). Africa has 253x the population of NZ.
cnorthwood 6y ago
16 fibre pairs doesn't seem like very much? I wonder what the constraining factors are, as surely the material costs of having hundreds of pairs are negligible compared to the install costs? Is it amplification?
- bluedino 6y ago
  You need repeaters every so often. Also, someone will "buy" each cable, like Microsoft/Google/etc. You need one cable for each fiber, they aren't all in one bundle like fiber might come into your office.
- centimeter 6y ago
  Yeah, you periodically need amplification/signal conditioning hardware in the cable. If it was just fibers you could put a ton in there. The amplification is obviously there for losses in the cable, but you also need to do clock recovery and thresholding because the light pulse gets spread out as it travels. Higher data rate => More analog bandwidth (distribution of frequencies from the laser) More analog bandwidth => Worse chromatic dispersion You need to either: * Increase the frequency of the laser (so BW/center frequency is smaller, hopefully reducing dispersion), which might not be possible with current tech or be very expensive * Decrease the dispersion of the fiber (more expensive or lossy fiber) * Have periodic signal conditioners
  - mmmBacon 6y ago
    It sounds like you are describing direct detect systems. These are no longer deployed in subsea. Due to the advent of coherent optical transmission and DSP, dispersion is no longer an issue for long distance optical communication. The limitation becomes nonlinear “crosstalk” between wavelengths and lower dispersion makes the nonlinear crosstalk worse as the phase matching condition for nonlinear processes can be reached more easily. To avoid this most new subsea cables use a high dispersion design as this helps mitigate nonlinear effects. Additionally coherent systems have a higher spectral efficiency and are transmitting >2bits/symbol because the information is encoded in the electric field’s phase and not just intensity. Depending on the reach, the number of bits per symbol can be increased. The advent of probabilistic shaping, allows more bits per symbol to be transmitted in higher order constellations. Probabilistic shaping produces a more ‘random-like’ coding that gets us closer to the Shannon Limit and also reduces the optical intensity rms further reducing nonlinear penalties. In fact in optical communications there is something called the nonlinear Shannon limit that takes into account the additional “noise” produced by nonlinearities in the fiber. See: https://arxiv.org/abs/1802.09120 https://arxiv.org/abs/1802.09120
ejanus 6y ago
They should have more African partners.
- zo1 6y ago
  Why should they?
  - mschuster91 6y ago
    Because everything other is just plain old neo-colonialism: Western companies with loads of money build the infrastructure and extract all the profits out of the African continent.

jeffbee 6y ago

Interesting in terms of scale. That's only about twice the capacity of the fiber connecting California and the almost negligibly-populated nation of Chile. On a per-capita basis Africa needs a lot of cables to Asia and Europe to gain parity.

nine_k 6y ago
But past the thin mountainous band of Chile lay large,populous, and reasonably advanced nations of Brazil and Argentina. Likely they share some of the bandwidth.
ejanus 6y ago
Google [1] is building one too but for their internal use. [1] https://businesstech.co.za/news/broadband/326323/google-is-building-a-super-fast-subsea-cable-between-portugal-and-south-africa/ https://businesstech.co.za/news/broadband/326323/google-is-b...
teruakohatu 6y ago
For comparison the main internet cable connecting my country, New Zealand, to the USA as 10 tb capacity and the cable connecting us to Australia has around 20 tb, so we have a theoretical maximum of 30 tb of overseas capacity for 4.8 million people (in practice Australian traffic will also be routed over our USA cable). We should have an additional 70+ tb by the end of 2022 after cable upgrades (again, shared with Australia). Africa has 253x the population of NZ.

cnorthwood 6y ago

16 fibre pairs doesn't seem like very much? I wonder what the constraining factors are, as surely the material costs of having hundreds of pairs are negligible compared to the install costs? Is it amplification?

bluedino 6y ago
You need repeaters every so often. Also, someone will "buy" each cable, like Microsoft/Google/etc. You need one cable for each fiber, they aren't all in one bundle like fiber might come into your office.
centimeter 6y ago
Yeah, you periodically need amplification/signal conditioning hardware in the cable. If it was just fibers you could put a ton in there. The amplification is obviously there for losses in the cable, but you also need to do clock recovery and thresholding because the light pulse gets spread out as it travels. Higher data rate => More analog bandwidth (distribution of frequencies from the laser) More analog bandwidth => Worse chromatic dispersion You need to either: * Increase the frequency of the laser (so BW/center frequency is smaller, hopefully reducing dispersion), which might not be possible with current tech or be very expensive * Decrease the dispersion of the fiber (more expensive or lossy fiber) * Have periodic signal conditioners
- mmmBacon 6y ago
  It sounds like you are describing direct detect systems. These are no longer deployed in subsea. Due to the advent of coherent optical transmission and DSP, dispersion is no longer an issue for long distance optical communication. The limitation becomes nonlinear “crosstalk” between wavelengths and lower dispersion makes the nonlinear crosstalk worse as the phase matching condition for nonlinear processes can be reached more easily. To avoid this most new subsea cables use a high dispersion design as this helps mitigate nonlinear effects. Additionally coherent systems have a higher spectral efficiency and are transmitting >2bits/symbol because the information is encoded in the electric field’s phase and not just intensity. Depending on the reach, the number of bits per symbol can be increased. The advent of probabilistic shaping, allows more bits per symbol to be transmitted in higher order constellations. Probabilistic shaping produces a more ‘random-like’ coding that gets us closer to the Shannon Limit and also reduces the optical intensity rms further reducing nonlinear penalties. In fact in optical communications there is something called the nonlinear Shannon limit that takes into account the additional “noise” produced by nonlinearities in the fiber. See: https://arxiv.org/abs/1802.09120 https://arxiv.org/abs/1802.09120

ejanus 6y ago

They should have more African partners.

zo1 6y ago
Why should they?
- mschuster91 6y ago
  Because everything other is just plain old neo-colonialism: Western companies with loads of money build the infrastructure and extract all the profits out of the African continent.