A high-power optical fiber laser includes: an oscillator (1); a pumping laser (5) able to emit a high-power pumping optical radiation beam; and a signal-amplifying optical fiber (3) able to receive the optical source signal and the high-power pumping optical radiation beam so as to generate a high-power laser beam. The pumping laser includes a plurality of pumping multimode laser diodes (7a-7f) and a laser cavity, the laser cavity including a double-clad fiber (4) including: a neodymium-doped monomode waveguide; a fiber Bragg grating (9) forming one end of the laser cavity; and a fiber reflector (11) forming the other end of the laser cavity, the monomodefiber laser being able to generate a laser radiation beam when it is optically pumped by a pumping radiation beam originating from the plurality of pumping laser diodes in order for the laser cavity to emit a high-power pumping laser radiation beam.