Two practical issues are investigated for asynchronous measurement-device-independent quantum key distribution (asynchronous MDI-QKD) operated with dense wavelength-division multiplexing (DWDM): the choice of the post-matching window ( \(T_c\) ) and the impact of adjacent-channel crosstalk on the secret key rate. Within a three-intensity decoy-state protocol with finite-size effects, a quantitative key-rate model is developed that links transmission distance, post-matching statistics, and phase-error accumulation, enabling the distance-dependent optimal \(T_c\) to be determined. The model is then extended to multi-channel DWDM by incorporating a crosstalk-induced effective detector-noise model that scales with the number of wavelength channels. Building on this unified framework, full parameter optimization of signal/decoy intensities and their sending probabilities is performed using a local search algorithm. Numerical results provide practical design guidelines, indicating when the optimal \(T_c\) is essentially insensitive to channel count and when DWDM scalability is ultimately constrained by crosstalk growth.
