Design of all-fiber 2D MMI based optical devices using 1D mode propagation method

We show that the mode propagation analysis in a 2D confined optical device can be bifurcated into two 1D problems. In our method, a given 2D launch field profile is divided into two 1D profiles and suitably aligned with the 1D waveguide, acting as independent launching conditions. This method shows that the complete propagation problem of a 2D waveguide, which involves the computation of 2D mode field profiles and their propagation constants, can indeed be solved as two 1D problems. Our method is verified with the beam propagation method through a commercial simulator. Based on our analysis, we design MMI-based optical devices using square core multimode optical fiber such as wideband power divider and combiner at 1550 nm. Furthermore, the practical considerations, such as fabrication tolerance and operation bandwidth for these devices, are investigated to ascertain operational advantages.