Rib waveguide as a three-mode demultiplexer for SOI

A flying-bird mode-division demultiplexer (FBMDD) that can demultiplex three modes is proposed. The demultiplexer is simply a modified rib waveguide, called a j-rib, followed by three fan-out waveguides. The fan-out waveguides are three single-mode strip waveguides, attached to the center, right, and left regions of the j-rib waveguide. The input of the j-rib waveguide is excited by three modes, e.g., EH11, EH12, and EH13. The waveguide is designed so as to separate the modes and guide them to the center, right, and left regions, respectively. The separated modes are then fanned-out to the output ports. A theoretical analysis of the proposed demultiplexer is developed based on extensions of the large single-mode rib conditions. In addition, both MODE and 3D-FDTD simulations of the demultiplexer are performed to validate the proposed concept. Our results reveal that the device has low insertion losses and crosstalks over a very wide bandwidth. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement