Amazon is building a subsea fiber-optic cable called Fastnet to connect Maryland’s Eastern shore to County Cork, Ireland, in what will be the company’s first wholly-owned subsea cable project.

Subsea fiber-optic communication cables carry over 95% of international data and voice traffic across the globe. These cables transmit hundreds of terabits of data per second including government communications, financial transactions, email, video calls and streaming.

Amazon has invested in several subsea cable projects in the past, including Jako, Bifrost and Havfrue as part of a consortium, but Fastnet is the first time that the tech company undertakes one of these projects alone.

“Subsea is really essential for for AWS and for any connectivity internationally across oceans,” Matt Rehder, Amazon Web Services vice president of core networking, told CNBC in an interview about Amazon’s subsea cable investments.

“Without subsea you’d have to rely on satellite connectivity which can work,” he said. “But satellite has higher latency, higher costs and you just can’t get enough capacity or throughput to what our customers and the internet in general needs.”

Amazon says that Fastnet’s capacity will exceed 320 terabits per second, which is equivalent to streaming 12.5 million HD movies simultaneously. The company is building this cable to meet rising demand for cloud computing, artificial intelligence and edge applications that use Amazon Web Services.

Fastnet will also strengthen Amazon’s network resilience. Amazon did not say how much Fastnet would cost to construct, but the company said it expects it to be operational by 2028. Other technology giants including Google, Meta and Microsoft have also been investing in subsea cable infrastructure.

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