SILICON VALLEY — At the Amazon Web Services networking lab in Mountain View, California, on the 9th, server racks blanketed in yellow optical cables filled the research floor. The yellow cables ran through transceivers, devices that send and receive electrical and optical signals, connecting rack trays about 50 centimeters wide as well as the racks standing side by side. It was the first time AWS, the world's largest hyperscaler, opened its networking lab to Korean media.
Optical fiber is the core of the network. AWS researchers introduced hollow core fiber, or HCF, which they described as the next generation of optical fiber. Optical fiber sits inside the cables that shuttle data between servers in a data center, and its diameter is measured in micrometers, or millionths of a meter, roughly the thickness of a human hair. Conventional fiber is filled with a solid such as glass, but hollow core fiber holds air at its center. Inside the fiber, light travels quickly through an air channel surrounded by high-purity silica.
The technology draws on the fact that light bends less in air than in a solid such as glass and therefore passes through more quickly. Switching the transmission medium from glass to air raises transmission speed 50% to 300,000 kilometers per second from 200,000, and sharply increases bandwidth, the volume of data carried per second. Conventional fiber has latency of 5 microseconds per kilometer, or millionths of a second, while hollow core fiber records only 3.3 to 3.5 microseconds. Using hollow core fiber extends reach 50% and improves latency 30% compared with conventional fiber.
AWS operates 123 data center groups across 39 cloud regions serving 245 countries and territories. The optical fiber cable AWS has laid undersea, underground and above ground to link the interiors of its data centers and to connect scattered facilities stretches 20 million kilometers. That is enough to circle the Earth, with a circumference of 40,000 kilometers, 500 times, or to make 25 round trips between the Earth and the moon. Hollow core fiber is drawing attention as a technology that can overcome the physical distance limits of data centers. As power, land and water constraints and local opposition make it increasingly difficult to build one large facility in a single location, connections through optical fiber grow more important. AWS is currently linking more than 10 separate data centers with hollow core fiber.
Rivals are also adopting hollow core fiber, but AWS has sought to differentiate itself with optical transponders, or signal converters, for dense wavelength division multiplexing, a specialized networking technology. An optical transponder allows light data on different wavelengths to travel through a single fiber optic cable, much as freight trains run on parallel tracks. That is why a single AWS optical cable can carry movie streaming, online payments and cloud applications at once. AWS optical transponders increase bandwidth 73% and cut power consumption 35% compared with earlier products. Satish Vangala, director of network product engineering at AWS, said AWS is the only company able to use DWDM optical transponders on long-haul networks.
The artificial intelligence industry points to graphics processing units and high-bandwidth memory as bottlenecks, but AWS argues that networks matter as much as chips. Stephen Callaghan, principal engineer for network development at AWS, said that in Project Rainier, the company's ultra-large AI infrastructure effort, there are sites handling more than one million chips. "In those places, a problem in any single part of the network stops every GPU," he said. "GPUs have to proceed sequentially through every task, like an army moving in perfect order," he added. "Our principle has been to keep the network running in optimal condition so that customers can focus only on their GPUs."
The global optical fiber market is projected to grow to $15.45 billion in 2032 from $7.36 billion in 2024, according to Data Bridge Market Research. AWS has built its own hollow core fiber procurement system with manufacturers and has been deploying the fiber in data centers since 2024. Matt Leder, senior vice president of network engineering at AWS, said the scale of AI is becoming enormous and everything runs through data centers. "Our goal is to extend reach without latency using hollow core fiber," he said.
