  The Optical Darboux Transformer is introduced as a photonic device which
performs the Darboux transformation directly in the optical domain. This
enables two major advances for signal processing based on the nonlinear Fourier
transform: (i) the multiplexing of different solitonic waveforms corresponding
to arbitrary number of discrete eigenvalues of the Zakharov-Shabat system in
the optical domain, and (ii) the selective filtering of an arbitrary number of
individual solitons too. The Optical Darboux Transformer can be built using
existing commercially available photonic technology components and constitutes
a universal tool for signal processing, optical communications, optical rogue
waves generation, and waveform shaping and control in the nonlinear Fourier
domain.
