266.1-Tbit/s Transmission Over 90.4-km 6-Mode Fiber With Inline Dual C+L-Band 6-Mode EDFA

We demonstrate a 6-mode and 580-wavelength multiplexed transmission with an inline C+L-band 6-mode erbium-doped fiber amplifier (6M-EDFA). This is the first demonstration of amplified transmission with a C+L-band few-mode EDFA. The 6M-EDFA is designed with an extremely wide erbium-doping profile to cover all spatial modes with population inversion uniformly, thus, suppressing differential modal gain within 5.6 dB in both C-band (1535-1563 nm) and L-band (1574-1602 nm) for the total input signal power of +3 dBm. As a transmission line, we use an 11.3-km 6-mode 19-core fiber and connect eight cores of the fiber to emulate transmission fiber spans. Although the transmission line includes additional losses of fan-in/fan-out devices for the connection between cores, transmission over 90.4 km is successfully demonstrated. The total capacity and spectral efficiency reach 266.1 Tb/s and 36.7 bit/s/Hz, respectively.