Abstract: The aim of the present description is a system for generating high peak power laser pulses including a light source for emitting initial nanosecond laser pulses, a fiber-based device for conveying laser pulses, including at least one first multimode fiber with a single core, a diffractive optical element and an optical system that generates, from each of said initial laser pulses, a laser pulse, the spatial intensity distribution of which on an input face of said first multimode fiber includes a “top hat” component summed with a speckle pattern. The system further includes a spatial shaping module that transforms a first electric field into a second electric field formed by a sum of N components that are at least partially spatially incoherent with one another, N?2, such that the contrast of said speckle pattern is limited compared to an initial contrast defined without a spatial shaping module.