A multi-orbital-angular-momentum multi-ring micro-structured fiber with ultra-high-density and low-level crosstalk

In this paper, a novel multi-orbital-angular-momentum multi-ring micro-structured fiber (MOMRMF) is proposed for the first time. This compact MOMRMF is presented with 19 rings, each ring supporting 36 modes (34 of them are OAM ones i.e., 684 channels in total) over the whole C wavelength band (1520-1580 nm). Due to the large refractive index difference between silica and air, the effective refractive index (neff) differences between the adjacent eigenmodes are all larger than 10−3, which is practically impossible to gain in other traditional high-density OAM fibers fabricated by modified chemical vapor deposition (MCVD) method. Compared with the trench-assisted multi-OAM multi-ring fiber (TA-MOMRF), the lower-level inter-ring crosstalk in the designed MOMRMF also can be achieved by the air hole-assisted. It is believed that both the high-density and low-level crosstalk make such a fiber of great potential in the space-division multiplexing (SDM) system.