A novel approach to generate and distribute ultra-wideband (UWB) pulses in optical domain is investigated. In this proposed scheme, a dual-electrode Mach-Zehnder modulator (DE-MZM) is biased at its quadrature point so as to realize the linear response. Then the intensity of output optical field can be assumed to the subtraction of two input Gaussian pulses. If the input Gaussian pulses are with the same sharp parameters but different time delays, a quasi-monocycle-waveform UWB signal can be generated. If the input Gaussian pulses are with different amplitudes and full-width at half-maximum (FWHM), a quasi-doublet-waveform UWB signal can be generated. A transmission of the UWB signals through a 25-km single mode fiber is carried out successfully. The results in both temporal and frequency domains are also presented.