  We study numerically and experimentally supercontinuum generation in optical
fibers with dark and bright solitons simultaneously contributing into the
spectral broadening and dispersive wave generation. We report a novel type of
weak trapped radiation arising due to interaction of bright solitons with the
dark soliton background. This radiation expresses itself as two pulses with the
continuously shifting spectra constituting the short and long wavelength limits
of the continuum. Our theoretical and experimental results are in good
agreement.
