Design of steering wheel-type ring depressed-core 10-mode fiber with fully improved mode spacing

We present a steering wheel-type ring depressed-core few-mode fiber (SWTR-DC-FMF) that features a central depressed step-index core and a novel SWTR structure consisted of two symmetrical high-index parts and low-index parts, respectively. The DC and SWTR make great contribution to separate the non-degenerated LP modes and spatial modes in the circular symmetry core, resulting in fully improved mode spacing. The designed fiber is able to support 10 spatial modes with the minimum effective index difference (Min Δ n eff ) between adjacent spatial modes larger than 1.93 × 10 −4 and the Min Δ n eff between adjacent LP modes above 1.51 × 10 −3 at the same time, facilitating potential fiber spatial mode multiplexing transmission with less multiple-input multiple-output (MIMO-less) digital signal processing technique. The broadband performance including n eff , Δ n eff , effective mode area ( A eff ) and differential mode delay ( DMD ) is comprehensively investigated over the whole C and L band. Moreover, the birefringence and fabrication tolerance are discussed. The designed fiber targets emerging applications in short-reach weakly coupled space-division multiplexing (SDM) optical networking to increase transmission capacity and spectral efficiency and further reduce the system complexity effectively.