Domain decomposition methods for solving Helmholtz equation are considered. Such methods rely on transmission conditions set on the interfaces between subdomains. The convergence of the iterative algorithm used to solve the associated linear system depends on these transmission conditions. Optimized transmission conditions (such as proposed in [1]) usually rely on transparent boundary conditions or local operators that are an approximation of the exact transparent boundary condition. In this talk, non-local optimized transmission conditions based on Riesz potentials as detailed in [2] are studied. The non-local operators can be replaced by quasi-local operators, and the obtained rate of convergence is independent of the mesh size. These conditions are applied to higher order finite element methods.