Numerical Simulation of Grating Couplers for Mode Multiplexed Systems
  A numerical investigation of a two dimensional integrated fiber grating coupler capable of exciting several LP fiber modes in both TE and TM polarization is presented. Simulation results and an assessment of the numerical complexity of the 3D, fully vectorial finite element model of the device are shown. 
B. Wohlfeil, S. Burger, C. Stamatiadis, J. Pomplun, F. Schmidt, L.   Zimmermann, K. Petermann
physics.optics