A new 4,300-mile (7,000-kilometer) undersea fiber cable will shuttle data between the U.S. and France at breakneck speeds of up to 1 million gigabits per second (Gbps) — enough to move around 125 terabytes of data every second, or roughly 25,000 HD movies, each 5 gigabytes large. The cable, called Petal, will be funded and operated by Facebook and Instagram parent company Meta.

When it comes online in 2029, the ocean-spanning cable will be the first to deliver petabit capacity — double the capacity of existing subsea cables of this length — across transoceanic distances, Meta representatives said in a statement. That's enough to allow 75% of the world's population to stream music at once.

Petal will also be the first commercial subsea cable system to use multi-core fiber technology, according to the statement. Whereas conventional fiber strands typically contain a single core, each of Petal's fiber strands will contain two cores that carry optical signals in opposite directions, allowing a single strand to provide the capacity that would conventionally require a pair of single-core fibers.

Each fiber strand is roughly as thick as a human hair, measuring just 125 micrometers in diameter. Petal will contain 24 pairs of dual-core fibers, giving it 96 individual fiber cores in total and enabling it to carry as much data as 48 conventional fiber pairs, Meta engineers said.

Japanese technology company NEC will be responsible for the overall design and construction of Petal, while Sumitomo Electric will provide the fiber itself.

"Achieving petabit-per-second capacity across a transoceanic submarine system represents a major technological milestone in the history of global telecommunications," Eduardo Mateo, chief strategy officer of the Submarine Networks Division at NEC, said in the statement.

Bedrock of the internet

Subsea cables are among the most critical layers of internet infrastructure, carrying around 99% of the world's internet traffic, according to the International Telecommunication Union, the United Nations ​agency for digital technologies.

Installing thousands of miles of fragile glass cable on the ocean floor is an engineering feat in itself. Equally challenging is ensuring that these cables can carry the tiny pulses of infrared light that transport fiber-optic data across such huge distances without impacting performance.

This is typically achieved through repeaters — amplifiers installed at regular intervals along the cable that use lasers to boost the optical signals.

A 4,300-mile subsea cable typically needs about 100 of these repeaters to amplify the signals along its length, Meta representatives said.

Petal will incorporate something called "fan-in/fan-out" technology. As each two-core fiber strand enters a repeater, an optical interface routes the signal from each core into a separate single-core fiber strand so that each can be amplified independently. The amplified signals are then routed back into the two cores of the dual-core fiber before continuing along the cable.

Combined with its dual-core fiber, this feat of signal engineering will enable Petal to double its data-carrying capacity without requiring a proportional increase in power, Meta representatives said.

Petal is one of many subsea cable investments by Meta in recent years, including Marea in 2018, Amitie in 2023 and Anjana in 2025. Marea, the company's first transatlantic fiber instalment, supports 192 Tbps, meaning Petal will offer more than five times that capacity.