Fused Fiber Mode Couplers for Few-Mode Transmission

Space-division multiplexing (SDM) based on few-mode fibers has been studied as a promising technique to increase fiber capacity. In this letter, we show optimal design and simulation of a low-loss fused fiber mode coupler, one of the most critical enabling components for SDM transmission systems. We first analyze the performance of a 3 × 1 fused fiber mode coupler with asymmetric waveguide structure by fusing a single-mode fiber and a two-mode fiber (TMF) together. A minimum loss of <; -1.9 dB and extinction ratio above 19 dB is predicated for both LP₁₁ modes, over a wide wavelength range of 1505-1600 nm. We then analyze the performance of another fused fiber mode coupler with symmetric waveguide structure by fusing two TMFs together. A minimum loss of below 0.4/0.7 dB is predicated for both LP₁₁ and LP₀₁ modes.