Suppression of crosstalk between solitons in a multi-channel split-step system

We consider collisions of solitary pulses in two wavelength-separated channels in a fiber-optic link consisting of long linear dispersive sections alternating with short nonlinear ones. If the collision distance Z_coll is essentially smaller than the length L of the linear segment, a probability that solitons overlap with a nonlinear section in the course of their collision is small, hence inelastic effects produced by the collision, which are very detrimental in the context of data transmission, get suppressed in comparison with uniform nonlinear fiber links. However, an estimate for the case of top interest, with the wavelength separation between the channels ∼0.1 nm (corresponding to dense wavelength-division-multiplexing) and temporal width of the pulse ∼20 ps yields Z_coll/L∼1, hence it is necessary to perform detailed simulations of the interchannel collisions between solitons in this system. The result is that collision-generated velocity changes and energy loss are suppressed by a factor ≈2, as compared to the uniform link. Interactions between solitons inside one channel are investigated too, but in that case the results are almost identical to those for uniform links. Besides the relevance to the applications, the problem considered is of interest in connection to a recently established class of nonlinear optical models in the form of periodic heterogeneous waveguides, which may support very robust solitary-wave modes.