The proposed multi-spot beam shaping method presents a combination of fiber end imaging and geometrical separation of focused spots perpendicular to the optical axis, thus creating a compound working spot, called as quattroXX-spot or peaXXus-spot, as a combination of. The proposed multi-spot beam shaping method presents a combination of fiber end imaging and geometrical separation of focused spots perpendicular to the optical axis, thus creating a compound working spot, called as quattroXX-spot or peaXXus-spot, as a combination of. Here we explore a highly multimode fiber amplifier, where stimulated Brillouin scattering is greatly suppressed due to reduction of light intensity in a large fiber core and broadening of Brillouin scattering spectrum by multimode excitation. To control the output beam profile, we apply spatial. We show numerically that the beam propagation factor 2 of a single-frequency multimode fiber amplifier can be reduced to nearly unity by shaping the input or output beam profile with spatial phase-masks. Our method works for narrowband multimode fiber amplifiers with strong gain saturation, pump. HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific re-search documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or pri-vate research centers. L'archive ouverte. Significant performance improvement of modern laser technologies such as welding, additive manufacturing, brazing, cladding, sheet metal cutting, based on the use of multi-kW multimode fiber lasers, fiber-coupled solid-state and diode lasers, can be improved using beam shaping optics providing. We present a new approach for shaping light at the output of a multimode fiber by modulating the transmission matrix of the system rather than the incident light.