A fully integrated waveguide-based, efficient surface plasmon coupler composed of a realistic non-tapered dielectric waveguide with graphene patches and sheet is designed and optimized for the infrared. The coupling efficiency can reach nearly 80% for a coupler as short as 700 nm for an operating wavelength of 12 μm. This work is carried out using rigorous numerical models based on the finite element method taking into account 2D materials as surface conductivities. The key numerical results are supported by physical arguments based on modal approach or resonance condition.