META ANNOUNCES PETAL, THE FIRST PETABIT-CAPACITY TRANSOCEANIC SUBSEA CABLE, USING 2-CORE FIBER

Summary from the TLDR Hardware newsletter

Meta's Petal cable will span roughly 7,000km between France and the US, carrying 1 petabit per second, double the capacity of any subsea cable at transatlantic distance, becoming the first system to deploy multi-core fiber at scale. Since the 2010s, coherent optical transmission pushed fiber capacity 10x before hitting the Shannon Limit, forcing the industry toward spatial division multiplexing, adding more fiber pairs to a cable, which Meta scaled from 8 pairs on Marea to 24 on Anjana. Rather than pushing to 48 fiber pairs or widening the optical band, Petal packs 2-core fiber into a 24-pair system, physically equivalent to 48 pairs but using ultra-pure synthetic silica and carefully controlled refractive-index differences between the cores to keep crosstalk nearly immeasurable.