Interconnecting data based on vortex beams by adjusting the ellipticity of a ring-core fiber.

Abstract

In order to exchange data in a space-division multiplexing (SDM) system, a novel vortex-beam-based data interconnection concept, which is achieved by adjusting the ellipticity of a ring-core fiber, is proposed. A new ring-core fiber is also designed and fabricated for exchanging and propagating the data carried by first- or second-order vortex (orbital angular momentum) beams. The proposed scheme is not only analyzed and simulated in principle, but is also verified through experiments. The numerical results demonstrate that the vortex beams can be exchanged by appropriately adjusting the phase difference (with respect to the ellipticity of a ring-core fiber) between the even and odd vector modes. A new experimental platform is designed and established for the sake of investigating the feasibility of the proposed scheme. The experimental results are consistent with the results of the simulation, and demonstrate that the data carried by the first- or second-order vortex beams can be successfully switched with acceptable bit error rates (BERs) between the first-order vortex beams (L=1 or -1) or between the second-order vortex beams (L=2 or -2, left or right circular polarization), respectively. The measured BERs and constellation diagrams of 16-QAM are employed to evaluate the data exchange performance with respect to different cases (i.e., data exchange once or twice, and data exchange with or without crosstalk). The measured BERs and constellation diagrams also demonstrate that the performance degrades with increase in topological charge or crosstalk. The proposed scheme is flexible, simple, and reliable for data exchange in a SDM system.