One way to excite a dark envelope soliton is to use a dark input pulse – a narrow dip in the amplitude of a continuous wave background. This approach has been used previously to excite dark solitons for surface spin waves in yttrium iron garnet (YIG) thin film strips and for lasers in photorefractive crystals.
Theoretically, however, an initial dark signal should not evolve into a single dark soliton, but a pair of dark solitons that have opposite phase jumps and an overall phase change of zero. Experimentally, such dark soliton pairs have been observed for solitons in various systems, but their phase signature has never been demonstrated so far.