Numerical Comparison of WDM Interchannel Crosstalk in FOPA- and PPLN-Based PSAs

We propose a model and numerical simulations to calculate crosstalk (XT) between multiple wavelength-division-multiplexing (WDM) channels in copier + phase sensitive amplifier (PSA) chains based on periodically poled lithium niobate (PPLN). The calculated XT is compared with XT generated in copier + PSA chains based on highly nonlinear fiber (HNLF). For ordinary device parameters, the results show that for an increasing channel number, the growth of interchannel XT in PPLN is less rapid compared with HNLF, as a consequence of the finite quasi-phase matching band of PPLN. This ensures lower XT in PPLN-based chains for 18 channels, whereas HNLF chains show better XT performance for 4 channels.