25-THz O+S+C+L+U-band digital coherent DWDM transmission using a deployed fibre-optic cable

We demonstrate an O+S+C+L+U-band transmission system as an upgrade scenario from a C+L-band system for the first time. DWDM signals fully allocated in a record bandwidth of 25 THz are successfully transmitted over a 45-km deployed fibre-optic cable.