Photonic generation of ultrawideband signals by exploiting gain saturation of dark pump pulse with double undershoots in a highly nonlinear fiber

► The proposed scheme to generate UWB doublet pulse is alternative and simple. ► We exploit the gain saturation and optical parametric attenuation effects in HNLF. ► A flexible format swap between UWB doublet and monocycle pulses is realized. ► Dispersion management is unnecessary when distributing UWB over fiber. ► The quality of UWB pulse is improved by using UWB-over-fiber technology.