In addition to beating conventional telecom fiber on loss and latency, hollow-core fibers are enabling new approaches to applications like sensing, fiber lasers and optical tweezers. [University of Southampton]In standard silica fiber, the group velocity of light is about 2×10 8 meters per second, approximately 67% of the speed of light in vacuum, which results in a latency of around 5 microseconds per kilometer. HCFs offer a wealth of potential due to their unique optical properties, including ultra-low loss, low nonlinearity, and reduced latency.