Extended C+L Band 103.5-Tb/s WDM Transmission Over 1260-km With Hybrid Raman/EDFAs

Multi-band dense wavelength-division multiplexing (DWDM) has emerged as a leading strategy for scaling per-fiber capacity in modern optical transport systems. In this work, we experimentally demonstrate extended C+L-band transmission over ultra-low-loss G.654.E fiber, enabled by a hybrid Raman–EDFA line system implemented with in-house line cards that provide a continuous 103-nm gain window from 1524 to 1627 nm. On a 50-GHz channel grid, we transmit a 12-THz payload comprising 240 × 48-GBaud probabilistic constellation shaping 64-ary quadrature amplitude modulation (PCS-64QAM) channels over 1260.65 km in a recirculating fiber loop. Band-wise spectral equalization is realized by wavelength-selective switches in combination with per-channel entropy tuning. At the receiver, adaptive dispersion compensation is employed to dynamically track variations in the chromatic-dispersion coefficient induced by wavelength switching, while a 4×4 real-valued multi-input-multi-output (MIMO) least mean square (LMS) equalizer is used to mitigate I/Q-related impairments. Experimental results show that, along the entire transmission link, the combination of spectral flattening and per-wavelength entropy assignment yields nearly uniform per-channel Q-factors across the full bandwidth. Under the baseline receiver DSP chain, we achieve an aggregate gross line rate of 120.192 Tb/s and a net WDM throughput of 102.47 Tb/s. With additional offline digital backpropagation (DBP) applied to the received data, the aggregate net throughput further increases to 103.5 Tb/s.