Nineteen-core optical fiber is the world’s fastest

https://www.laserfocusworld.com/fiber-optics/article/14296150/19core-optical-fiber-is-the-worlds-fastest

"10 million high-speed full capacity home internet connections... 1.7 PB/s... exploiting different degrees freedom wavelength: multiplexing, polarization, and coherence (higher-order modulation formats)... over 67 km fiber... 125 µm cladding diameter... allow well-defined coupling between cores reduce existing digital signal processing requirements... >17X theoretical limit standard single-mode optical fiber... compact glass chip, etched waveguide pattern, uniform low losses... in parallel through optical amplifiers"

Related: Shrinking light: Waveguiding scheme enables highly confined subnanometer optical fields
https://phys.org/news/2023-07-waveguiding-scheme-enables-highly-confined.html