Design and fabrication of low-cost, ultra-compact polymer based multimode 4x4 star couplers

We report on the design and fabrication of compact and potentially low-cost multimode fiber matched 1 x N and N x N couplers for LAN’s. The design utilizes the self-imaging effect and tapering of the Multi-Mode Interference (MMI) section. An extended mode propagation analysis and 3-D beam propagation method (BPM) were used to analyze and design these structures. The simulations show that the couplers exhibit low excess losses, low power imbalance, and relaxed fabrication tolerances at very short device length. The devices were fabricated in polymer waveguide technology using spin coating, photolithography, and reactive ion etching. Preliminary experimental results show promising characteristics.