Japan sets internet speed record by transferring 319 Tb/s over 3,001 km

Space Division Multiplexing on Multi Core Fibers is a next generation transmission system it won't be long before any new long line runs will have MCF cable down in parallel to singlemode just sitting there waiting for the network equipment to catch up.

552 wavelengths each at 580 Gbps (PDM-16QAM) over a 4 split core fiber with amplifiers every 70km for 43 cycles. 957 Pb/s /km. Your move core switches.

Heres the more detailed source : https://www.nict.go.jp/en/press/2021/07/12-1.html