Meta plans a 1 Pbps transatlantic cable using two-core fiber
Petal is due in 2029, linking the US and France with twice the capacity of Meta's 0.5 Pbps Anjana system.
By Ryan Merket · Published
Primary source: Engineering at Meta on X
Why it matters
Petal would move multi-core fiber into a 7,000-kilometer operational system, giving hyperscalers another way to expand bandwidth without doubling cables, power and materials.
Meta plans to build a 7,000-kilometer subsea cable capable of carrying 1 petabit per second between the United States and France, doubling the design capacity of the most advanced transatlantic systems operating at that distance.
https://x.com/Meta_Engineers/status/2102117645986431134
The company announced Petal on September 21st, calling it the first petabit-class transoceanic cable and the first subsea system to deploy multi-core fiber at scale. Petal is expected to enter service in 2029.
Those records remain Meta's claims until Petal is built, installed and tested across the Atlantic. The engineering behind them is more concrete: Petal will put two independent paths for light inside each strand of a 24 fiber-pair cable, effectively delivering the capacity of a conventional 48-pair system without doubling the number of fibers packed into the cable.
Meta is working with NEC, which will manufacture and install the system, and Sumitomo Electric Industries, which will supply the two-core fiber. Orange is supporting plans to land the cable on France's Atlantic coast. Meta has not named the US landing site or disclosed the project's cost.
Two cores inside the same strand
The design attacks a physical constraint that has shaped recent subsea cable construction. Improvements in optical transmission have pushed conventional single-core fiber closer to its practical capacity limits, leading cable builders to add more fiber pairs through spatial division multiplexing.
Meta followed that route from Marea, an eight-pair transatlantic system, through the 16-pair Amitie cable and then Anjana. Anjana connected South Carolina and Spain with 24 fiber pairs and a design capacity near 0.5 Pbps.
Petal keeps the 24-pair architecture and adds a second core to each fiber. The two cores carry signals independently while retaining the standard 125-micrometer glass diameter of single-core fiber. Sumitomo began selling a mass-produced two-core fiber in 2023, after reporting transmission loss of 0.158 decibels per kilometer and counter-propagating crosstalk at or below minus 43 decibels.
Petal will use a version of that technology called 2C Z-PLUS Fiber ULL. According to Meta, ultra-pure synthetic silica reduces signal loss, while differences in refractive index and counter-propagating signals limit interference between the two cores.
The repeaters placed along the ocean floor present the harder systems problem. A cable of Petal's length typically requires about 100 repeaters to amplify signals. Meta's design uses a fan-in and fan-out interface that separates each two-core fiber into single-core paths inside the repeater, amplifies them and recombines them afterward.
Each repeater will contain 96 optical amplifiers in one body. Meta says that arrangement will keep Petal within existing power-feeding equipment rated up to 18 kilovolts, avoiding the industry requalification work that higher voltages would require. The company also says one 1 Pbps system will use fewer materials and less power than building two separate 0.5 Pbps cables.
Meta is laying its own growth curve
Petal extends Meta's shift from buying capacity on carrier networks to helping design and finance the physical routes connecting its data centers and users. The company says it has invested in more than 20 subsea cable projects.
Its largest announced undertaking is Project Waterworth, a planned cable network spanning more than 50,000 kilometers and five continents. Meta described that project as a multibillion-dollar investment intended to add capacity and route diversity for AI services and its existing applications.
Petal has a narrower route and a sharper technical purpose. Its planned capacity is twice Anjana's and 5.5 times that of Marea, Meta's first transatlantic cable investment. Meta says 1 Pbps is equivalent to 1,000 terabits per second.
The 2029 service date places Petal inside Meta's broader data center and AI infrastructure buildout. The company has separately said that one pair of sites on its newer AI backbone can require twice the network capacity of the global backbone it spent the previous decade constructing. Meta has not specified how much of Petal will serve AI traffic, Facebook, Instagram or WhatsApp, or whether it will make capacity available to outside customers.
Petal's larger consequence is the planned jump from manufacturing multi-core fiber to operating it across an ocean. If NEC and Sumitomo can install thousands of kilometers of two-core fiber while preserving the required loss and crosstalk characteristics, future cable builders gain another way to increase capacity without making each system proportionally larger or more power-hungry. Meta, meanwhile, gets a network designed around the traffic growth it expects rather than the capacity carriers already have available.