Segmented Power Optimization for Achieving 800 Gbps per-Channel Transmission in C+L+S Band Fiber Systems

Ultra-wideband optical transmission systems operating over the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$C+L+S$</tex> bands are critical for meeting the growing demand for high-capacity networks. However, existing power optimization strategies-typically based on coarse control using one slope and one offset per band-struggle to achieve sufficiently flat SNR profiles, especially in the L-band. To address this limitation, we propose a segmented power allocation approach that models the L-band power distribution as multiple linear segments, each controlled by offset and slope parameters. Using particle swarm optimization (PSO) under the ISRS GN model, we evaluate various segmentation strategies in a 181-channel, 20 THz WDM system targeting 800 Gbps per-channel transmission. Experimental results demonstrate that segmenting the L-band into three or four regions significantly reduces SNR ripple to below 0.2 dB, improves minimum achievable data rate to over 797 Gbps, and maintains acceptable optimization time, offering a superior trade-off between performance and complexity.