This study presents an eye-safe, single-mode, nanosecond-pulsed, and all-fiber laser source with master-oscillator-power-amplifier configuration at 1 550 nm that is suitable for high-resolution three-dimensional (3D) imaging light detection and ranging (LIDAR) system. The output peak power of 7.6 kW is obtained at the 1.2-ns pulse width and 50-kHz repetition rate. The single-mode pulse laser output ensures the range precision and imaging results of the LIDAR system. The laser is used as a transmitter for the 3D imaging LIDAR system. The detailed characteristics of the LIDAR system and the results of the 3D imaging are presented.