Low complexity fiber nonlinearity compensation scheme fusing single-channel digital back propagation with dual phase-conjugate twin waves for DSCM-WDM system

In coherent systems combining digital subcarrier multiplexing (DSCM) and wavelength division multiplexing (WDM), signals are subject to self-subcarrier nonlinearity (SSN), cross-subcarrier nonlinearity (CSN), and cross-phase modulation (XPM) after optical fiber transmission. Most typical nonlinear compensation schemes for inter-channel and inter-subcarrier nonlinearities rely on information from neighboring channels and subcarriers, resulting in high complexity. To address the above problems, we propose a nonlinear low complexity compensation scheme that combines single-channel single-step digital back propagation (SC-DBP) with dual phase-conjugate twin waves (dual-PCTW), referred to as SC-DBP-DPCTW. This scheme efficiently compensates SSN while addressing XPM and CSN without relying on information from adjacent channels. Simulation results for a 9 × 128-GBaud transmission over a 1600-km DSCM-WDM system using dual-polarized 16QAM modulation show that SC-DBP-DPCTW achieves the same Q-factor improvement as 10-Step DSCM-DBP while reducing complexity by approximately 92.2%. Additionally, in a 3 × 28-GBaud transmission over an 806.4-km DSCM-WDM experimental system, the scheme provides the same Q-factor improvement as 5-Step DSCM-DBP with a complexity reduction of approximately 84.3%.