Prysmian’s 1 Petabit per second fibre transmission speed record

We decided to take a different approach, using space division multiplexing technology. This allows you to use multiple core or modes inside a fibre. You can fit four cores in a standard 125 µm fibre but with more than four you get crosstalk issues between cores, degrading the signals transmitted in the fibre. If you want to add cores the diameter increases to 150 µm and up to 250µm – twice the diameter of a standard fibre. This is necessary to avoid crosstalk issues. The larger fibre means many standard practices and measurements no longer apply. Mechanical reliability is degraded, and splicing becomes more complex.

Instead, we decided to add more modes, allowing us to keep to the 125µm limit. Our challenge was to increase speed while still working with a standard dimension fibre. We increased the core diameter from ~9 µm to ~28 µm and used 15 modes instead of one. That helped us to increase capacity by a factor of 10 to 15. There is some crosstalk between the modes, so digital signal processing is required at the reception end to recover information in each mode.