A novel scheme for all-optical ultra-wideband signal source based on semiconductor fiber ring laser (SFRL) is proposed, in which three monocycle signals can be generated simultaneously. The effect of the bias current of the semiconductor optical amplifier (SOA) in the SFRL, the wavelength of the lasing light, the power and the wavelength of input signal light on the performance of the monocycle signals are analyzed through numerical simulation. The results show that the output monocycle pulses with better symmetry can be obtained when the bias current of SOA is in a range of 200−220 mA. The average power, the amplitude of the positive and negative pulses of the output monocycle pulses increase as the wavelength of the lasing light increases. A better performance of the monocycle pulses can be obtained under lower input signal optical power. The wavelength of the input signal light has a little effect on the output monocycle pulses.