Spot-based mode coupler for mode-multiplexed transmission in few-mode fiber

We present designs for a low-loss mode coupler based on multiple Gaussian spots that can selectively address spatial and polarization modes of a few-mode fiber. In particular we show a design optimized for a few-mode fiber with 12 spatial and polarization modes (LP₀₁, the twofold degenerate LP₁₁ and LP₂₁, and LP₀₂), with a mode dependent loss <;1dB and coupler insertion loss <;3dB.