Broadband laser can be obtained using a LiNbO 3 electro optic phase modulator, furthermore, the width and the shape of the broadband laser pulse can be easily controlled by an electrical pulse generator. It is reported in this paper that using a LD pumped single longitudinal mode CW laser as the light source, the peak power and the whole band width of the broadband laser pulse obtained reach 4.2 mW and at least 42 GHz respectively.