Tapered fiber phase-conjugating mirrors (PCMs) have been experimentally investigated in a master-oscillator power amplifier system. The dependence of PCM properties such as threshold and reflectivity on the geometry of the fiber is discussed. The beam quality factor of the output beam was 1.2, and the peak power reached . In operation with 100-Hz repetition rates, the fluctuation of the output energy was 8%. A depolarization ratio of 3% and phase conjugation fidelity above 90% were also demonstrated.