A novel scheme is reported about optical short pulse with high extinction ratio,which is based on fiber-optical parametric amplifier and phase modulation added with dispersion compression.The continuous pump wave first passed through a LiNbO3 intensity modulator to generate optical pulses with 33% duty cycle based on the frequency-doubled modulation.Then through a phase modulator,the biggest liner positive chirps were imposed on the pulses.After optical parametric amplification,the chirps of the...