Design of weakly coupled 20-eigenmode bow-tie rectangular dual-step fiber for short-haul communication in O band

We present a weakly coupled bow-tie rectangular dual-step few-mode fiber supporting 20 eigenmodes for short-haul communication systems across the O band. The rectangular dual-step core and bow-tie stress-applying area are introduced to effectively split adjacent eigenmodes. We evaluate the impact of parameters on modal mode effective refractive index difference (MERID) Δneff, min Δneff, min Aeff, Bm, and bending loss at a wavelength of 1310 nm. Broadband performance of the entire O band, including neff, MERID Δneff, differential mode delay, and dispersion, is also analyzed. Results indicate that the 20 eigenmodes supported by the designed fiber are completely separated with MERID Δneff between adjacent modes larger than 2.319 × 10 − 4 over the whole O band. The designed fiber can be used for short-haul multiple-input multiple-output-free eigenmode-division multiplexing systems to improve transmission capacity and expand bandwidth.