Quality of transmission optimization in a multi-band optical system: a stepwise multi-device joint configuration algorithm

Performance optimization in ultra-wideband transmission systems becomes increasingly complex due to the higher number of configurable components and the amplified impact of fiber nonlinearities, such as the stimulated Raman scattering effect. To address these challenges and advance multi-band transmission systems toward comprehensive optimization, we propose a stepwise algorithm to jointly configure multiple devices, enhancing the performance of ${\rm S} + {\rm C} + {\rm L}$-band transmission systems. This stepwise configuration approach accelerates the identification of optimal configurations by considering various linear and nonlinear effects while incorporating adjustments to multiple devices beyond in-line amplifiers. This flexibility allows for tailored optimizations under varying conditions, achieving improved performance at a reduced cost. A simulation study of an eight-span ${\rm C} + {\rm L} + {\rm S}$-band link demonstrates that optimizing amplifiers alone using the proposed algorithm achieves a comparable 2.2 dB improvement in generalized signal-to-noise ratio (GSNR) while reducing the optimization time by half compared to traditional methods. Further configuring wavelength-selective switches (WSSs) improves GSNR flatness—reducing the difference between maximum and minimum GSNR values to below 0.2 dB in each band, even under uneven amplifier gain spectra. Additionally, an efficient method for simultaneously configuring WSS in multiple adjacent channels reduces optimization time by approximately tenfold.