A Weakly-Coupled Double Bow-Tie Multi-Ring Elliptical Core Multi-Mode Fiber for Mode Division Multiplexing across C+L+U Band

Abstract

We herein present a weakly-coupled double bow-tie multi-ring elliptical core multi-mode fiber (DBT-MREC-MMF) supporting 22 eigenmodes for mode division multiplexing across the C+L+U band. The proposed fiber introduces a multi-ring elliptical core, bow-tie air holes, and bow-tie stress-applying areas to effectively split adjacent eigenmodes. By utilizing the finite element method (FEM), we accordingly optimized the fiber to support the 22 modes under the weakly-coupled condition. We evaluated the impact of fiber parameters on the minimum effective refractive index difference (min Δneff) between adjacent eigenmodes, model birefringence (Bm), and bending loss at a wavelength of 1550 nm. Additionally, broadband performance metrics, such as effective modal index (neff), effective index difference (Δneff), effective mode area (Aeff), differential mode delay (DMD), and chromatic dispersion (D), were comprehensively studied over the entire C+L+U band, ranging from 1530 to 1675 nm. The proposed fiber is capable of supporting 22 completely separated eigenmodes with a min Δneff between adjacent eigenmodes larger than 3.089 × 10−4 over the entire C+L+U band. The proposed DBT-MREC-MMF holds great potential for use in short-haul communication systems that require MDM to improve transmission capacity and expand bandwidth.