A group of researchers from the National Institute of Information and Communications Technology (NICT, Japan) and Sumitomo Electric Industries, Ltd. (SEI, Japan) in collaboration with the Eindhoven University of Technology, University of L’Aquila, and Macquarie University has developed a 19-core optical fiber with a standard cladding diameter (0.125 mm), which has the largest number of cores among the standard cladding diameter multi-core fibers, and has demonstrated large-capacity transmission at a data-rate of 1.7 petabits per second over a distance of 63.5 km. A randomly coupled multi-core fiber design was used to achieve high core density, as well as a multiple input multiple output (MIMO) digital signal processing to eliminate inter-core signal interference.