Design of a Weakly Coupled 19-Core 5-Mode-Group Fiber for Dense Space-Division Multiplexing

Few-mode multi-core fiber is a space-division multiplexing backup solution to address the communication capacity crunch which is limited by the capacity of single-mode fiber. In this paper, we propose a weakly coupled 19-core 5-mode-group trench-assisted ring-core fiber with ultra-high spatial channel number, which can support up to 380 usable spatial mode channels (19 cores x 5 radial first-order OAM mode groups x 4 degenerate modes). To our knowledge, this is the highest channel count reported for few-mode multi-core fibers. The fiber can stably transmit 5 OAM mode groups in the C+L band. The minimum effective index difference between adjacent radial first-order mode groups is 1.35×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup>. With limited cladding diameter, when the core pitch is 44 µm, the inter-core crosstalk for the high-order OAM<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5,1</inf> mode can reach −60.13 dB/100km.