Parasitic wavelength conversion between WDM channels in PPLN-waveguide-based optical parametric amplifier

Crosstalk (XT) component generation caused by parasitic wavelength conversion in the optical parametric amplification of wavelength division multiplexing (WDM) signals employing a periodically poled LiNbO 3 waveguide was investigated. It was found that appreciable XT generation arises from unintended sum-frequency generation between the signal and idler and subsequent difference-frequency generation. Both experimental results and numerical analyses confirm that increasing the number of signal channels leads to higher XT power and an increased number of XT peaks. At low input powers, XT-induced interference and signal degradation are negligible owing to the quadratic dependence of XT power on input signal power.