What is Microsoft Azure Hollow Core Fiber (DNANF)?

Microsoft Azure's hollow-core fiber deployment uses Double Nested Antiresonant Nodeless Fiber, an optical fiber design that guides light mainly through a hollow air-filled core instead of through solid glass, using a nested ring of thin glass tubes to confine the light without a solid core. Because light travels faster through air than through glass, hollow-core fiber links carry data with lower latency and different attenuation and dispersion characteristics than conventional solid-core optical fiber used across data-center and backbone networks.