Experimental Evaluation of Transmission of C+L+U Bands Over an Unrepeatered Link

We investigate the potential to expand the transmission bandwidth beyond the C-band to include the L- and U-bands over an unrepeatered link. We characterize three fibers - a G.654 compliant Sumitomo Z+ fiber, a G.657 compliant Corning SMF28ULTRA fiber, and a G.652 compliant OFS AllWave Zero Water Peak (ZWP) fiber - for their attenuation profiles and Raman gain efficiencies in the L- and U-bands. We demonstrate the transmission of C+L+U bands over an unrepeatered link of 257.1 km. The transmission system includes band-specific erbium-doped fiber amplifiers for the C- and L- bands, lumped Raman amplifiers for the U-band, and bidirectional distributed Raman amplification for the three bands. We report a decoded data-rate of 84.5 Tb/s over a spectral bandwidth of 109.2 nm using 520 polarization-multiplexed 16-ary quadrature amplitude modulated channels across C+L+U bands. We investigate ways to manage the effects of stimulated Raman scattering while expanding the transmission window beyond 100 nm over an unrepeatered link.