Compressive Strain Gradient for Stimulated Brillouin Scattering Mitigation in Optical Fibers

For applications such as mobile and airborne wind profiling Lidar, high-energy all-fiber laser systems with narrow spectral linewidth are required. In these lasers, non-linear effects, in particular Stimulated Brillouin Scattering (SBS), often limit the peak power and thus the Lidar range. In order to mitigate SBS in fiber laser systems, active methods (e.g. spectral broadening of incident light by laser phase control) or passive methods can be implemented. The latter consists in modifying the physical properties of the fiber. This can be achieved by applying a temperature gradient [1] or a stress gradient [2] in order to introduce a broadening of the Brillouin spectrum of a few hundred MHz. While temperature differences of several hundred degrees are required, only ∼ 1% tension or compression can be deployed on the fiber to achieve the necessary broadening. Compared to tension, compression causes less fiber weakening and is therefore a better candidate for maintaining the robustness and lifetime of the laser system.