Design of Multilayered Ring-Core Fiber With Low-Level Inter-Group Crosstalk

We propose a novel ring-core fiber (RCF) with multilayered ring core and modulated refractive index profile (RIP). The simulated results indicate that such a special fiber design is able to support 5 orbital angular momentum (OAM) mode groups (18 OAM modes) with crosstalk between any two high-order adjacent mode groups (MGs) less than −28 dB/km over the whole C and L band. At the wavelength of 1550 nm, crosstalk between the two highest-order MGs is below −36 dB/km. Besides, with the limitation of the existing manufacturing restriction, the geometric size and doping concentration of the designed fiber are allowable and reasonable, which is promising for practical manufacturing. The designed RCF also shows good bending characteristics. Moreover, ultra-broadband performance is analyzed over the whole C + L band ranging from 1530 nm to 1625 nm. This kind of fiber design could be employed in small-scale multiple-input multiple-output digital signal processing (MIMO-DSP) assisted intra-group modes multiplexing transmission or MIMO-free inter-group modes multiplexing transmission combined with the mature wavelength-division multiplexing technique.