Dynamic Discrete Crosstalk Model in Weakly-Coupled Multicore Fiber-Based IM/DD Systems

Intercore crosstalk (IC-XT) is an important impairment in weakly-coupled multicore fiber (WC-MCF)-based optical communication systems. A dynamic discrete XT model is proposed to characterize the role of phase matching points (PMPs) for IM/DD systems with high carrier-to-signal power ratio (CSPR) in the WC-MCFs. Besides, a sense-and-compensate method is utilized to estimate the cumulative XT coefficients of PMPs and validate the effectiveness of the proposed model. Experimental results validate the model by demonstrating the impact of internal factors, such as laser source stability, and external factors, including polarization and coupling variations, on XTdynamics. Using a fiber laser with low linewidth and phase noise, we observed stable XT coefficients, contrasting with the fluctuations seen with an external cavity laser (ECL). Moreover, the measured relative time delays and XT coefficients are applied to XT compensation via offline digital signal processing (DSP) in a 10-Gbaud on-off keying (OOK) and 4-pulse amplitude modulation (PAM-4) intensity-modulation direct-detection (IM/DD) system, achieving significant bit error rate (BER) improvements. Sensitivity improvements reach 2.7 dB for OOK and 4.8 dB for PAM-4 signals, with XT compensation performance improving at higher received optical power (ROP). These findings align closely with the proposed model, offering a robust framework for analyzing XT in MCF systems and guiding future equalizer designs.