Scalable low-modal-crosstalk mode-group demultiplexer for MDM transmission over MMF

Abstract

Weakly-coupled mode-division multiplexing (MDM) transmission technique over widely-deployed multimode fiber (MMF) is considered a promising approach to enhance the capacity of optical fiber communication systems. In order to be compatible with cost-efficient intensity-modulation/direct-detection (IM/DD) systems, effective mode-group demultiplexing approaches to simultaneously receive each mode group of MMF are highly desired. In this paper, we propose a scalable low-modal-crosstalk mode-group demultiplexer over MMF using multi-plane light conversion (MPLC), in which input Hermite-Gaussian (HG) modes of MMF are first converted to bridging modes that composed of HG 00 modes distributed as a right-angled triangle in Cartesian coordinates, and then each HG 00 mode belonging to the same mode group are respectively converted to different HG n0 modes at the same output for simultaneous detection. With the help of bridging modes, the MPLC-based mode-group demultiplexer can scale to demultiplex more mode groups with relatively few phase masks. A 5 mode-group demultiplexer is also design for demonstration, and simulation results show that the modal-crosstalk are lower than -22.26 dB for all mode groups.