A high-power and fully fibered optical fiber laser comprising: - an oscillator adapted to emit a source optical signal to be amplified, said oscillator comprising a fibered laser diode emitting at a wavelength of about 978 nm, - a pump laser adapted to emit a high-power pump optical radiation, - a signal-amplifying optical fiber, adapted to receive said source optical signal and said high-power pump optical radiation, - wherein said pump laser comprises a plurality of fibered multimode pump laser diodes (7a, 7b, 7c, 7d, 7e, 7f) emitting at 806 nm and a fully fibered laser cavity, said laser cavity comprising a double-clad fiber having a leaky-mode refractive index profile, of W-shaped type, and a neodymium-doped single-mode core, the double-clad fiber having a length of 25 m, a clad diameter of about 125 microns, a core diameter of about 5 microns, an optical fiber Bragg grating forming an end of said laser cavity and a fiber reflector forming the other end of said laser cavity, said double-clad fiber being adapted to generate a laser radiation at a wavelength of about 930 nm when it is optically pumped by a pump radiation at a wavelength of 806 nm coming from the plurality of pump laser diodes (7a, 7b, 7c, 7d, 7e, 7f) and injected into the multimode clad of the double-clad fiber, so that said laser cavity emits a high-power pump laser radiation at the wavelength of 930 nm, and - said signal-amplifying optical fiber comprises an Ytterbium doped single-mode optical fiber section, so as to generate a high-power laser beam in the vicinity of 978 nm, when said signal-amplifying optical fiber is optically pumped by said high-power pump optical radiation at the wavelength of 930 nm. - an oscillator adapted to emit a source optical signal to be amplified, said oscillator comprising a fibered laser diode emitting at a wavelength of about 978 nm, - a pump laser adapted to emit a high-power pump optical radiation, - a signal-amplifying optical fiber, adapted to receive said source optical signal and said high-power pump optical radiation, - wherein said pump laser comprises a plurality of fibered multimode pump laser diodes (7a, 7b, 7c, 7d, 7e, 7f) emitting at 806 nm and a fully fibered laser cavity, said laser cavity comprising a double-clad fiber having a leaky-mode refractive index profile, of W-shaped type, and a neodymium-doped single-mode core, the double-clad fiber having a length of 25 m, a clad diameter of about 125 microns, a core diameter of about 5 microns, an optical fiber Bragg grating forming an end of said laser cavity and a fiber reflector forming the other end of said laser cavity, said double-clad fiber being adapted to generate a laser radiation at a wavelength of about 930 nm when it is optically pumped by a pump radiation at a wavelength of 806 nm coming from the plurality of pump laser diodes (7a, 7b, 7c, 7d, 7e, 7f) and injected into the multimode clad of the double-clad fiber, so that said laser cavity emits a high-power pump laser radiation at the wavelength of 930 nm, and - said signal-amplifying optical fiber comprises an Ytterbium doped single-mode optical fiber section, so as to generate a high-power laser beam in the vicinity of 978 nm, when said signal-amplifying optical fiber is optically pumped by said high-power pump optical radiation at the wavelength of 930 nm. - said signal-amplifying optical fiber comprises an Ytterbium doped single-mode optical fiber section, so as to generate a high-power laser beam in the vicinity of 978 nm, when said signal-amplifying optical fiber is optically pumped by said high-power pump optical radiation at the wavelength of 930 nm.