META's New 1 Petabit Atlantic Cable

Facebook engineers during an interview on the Waterworth project provided details about their next big project.

1. Facebook is planning to build the first one petabit per second Atlantic cable. No details yet available on end points. Given traffic flows it is most likely to directly connect Continental Europe and the US.

2. META engineering is looking at three options to achieve one petabit per second throughput.

A. Using both the C and L spectrum. This would effectively double the bandwidth.

B. Cable will definitely be SDM (spatial division multiplexing). Strong likelihood that will be 48 pairs.

C. Another possibility is two core optical fibre in order to double the bandwidth per pair.

3. I believe the most likely option is using C and L bandwidth. Arelion has incorporated L band spectrum into its DWDM Layer 1 service between Atlanta data centers and Ashburn Equinix using Infinera gear. Colt and Sparkle have used the L band on terrestrial routes. Most DWDM equipment today offers both C and L band. There is no need for product development, research or physical modification, just a software upgrade. Subcom has deployed a C+L band subsea cable in the Pacific, namely PLCN, which connects Taiwan and the Philippines to the US. It was RFS 2022.

4. According to Subcom, an 8 fibre pair Trans-Atlantic cable using both the standard C band and adjacent L band spectrum can generate 325Tbps. That is 40.6 terabits per fibre pair. Note that a drawback is that the optical amplifiers will be bigger and more expensive, but that may also be true for multicore fibre as well. So achieving a 1 petabit cable appears eminently doable using standard spatial division multiplexing plus exploitation of the L band. What would help achieve the one petabit milestone would be an island hop in the Atlantic for power like Nuvem is doing using Bermuda or Azores. 

4. Two core optical fibre is another possibility. The Google-owned TPU cable links Taiwan and Philippines to the US. It uses two core optical fibre on the branching segments, but not the main trunk. NEC built the cable and also developed the multicore technology. I suspect there is less risk for META going with the L band as opposed to multicore fibre as the latter would be a first. Construction expense would be probably be less as well since the only multicore subsea vendor is NEC.

Map Of Trans-Atlantic Subsea Cables


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