Optical crosstalk in a periodically inhomogeneous nonlinear dispersion directional fiber coupler

We present a numerical investigation of the propagation and the switching of fundamental solitons in a two-core nonlinear fiber coupler constructed with periodically modulated dispersion fiber (PMDFC). Our simulations are taking into account different amplitude and frequency modulations of the PMDFC. The transmission characteristics, the critical energy, the compression factor, the crosstalk (Xtalk) and extinction ratio (Xratio) levels of the first order solitons were studied for low to high pump energies. It was observed that for low modulation frequencies, the augmentation of pump power leads to an increase of the critical energy and decrease of the transmission efficiency. For higher modulation frequencies the effect in the critical energy is minimum but at high pump powers the transmission is less efficient. The switched pulses are broader for low frequency and high amplitude of modulation. The Xtalk level is a decrease function with the increase of pump power, however it is getting worse with the augmentation of the amplitude of modulation. At higher frequencies, the increase of the amplitude modulation is leading the Xtalk to a minimum as a function of pump power. In summary, we have shown that the introduction of a periodically modulated dispersion profile is leading the nonlinear directional coupler to strong variations in the transmission efficiency, Xtalk and Xratio levels as a function of the modulation amplitude and frequency as well as pump energy.