LDPC-coded cylindrical vector beam multiplexing for improved communication performance

Cylindrical vector beams (CVBs) have attracted significant research interest in mode-division multiplexing communication thanks to their capacity to carry orthogonal vector modes. Because CVB modes are the eigensolutions of few-mode fiber (FMF), they are well-suited for long-distance transmission. Nevertheless, the application of CVB multiplexing communication is impeded by mode coupling in FMF, which leads to mode crosstalk and signal fading. Herein we propose an LDPC coded strategy to provide a channel equalization solution, which enhances the performance of CVB multiplexing communication. Digital signals are encoded using a sparse parity-check matrix that establishes a specific parity-check relationship between the original data bits and the check bits. This enables the correction of error bits for channel equalization. To demonstrate the concept, we built a 4-channel CVB multiplexing communication system that transmitted 24 x 4 Gbit/s QPSK-OFDM signals over 5 km FMF. After equalization, the bit error rate decreased by - 2.5 orders of magnitude, and the communication sensitivity improved by - 8 dB. This proof of concept demonstrates the potential of the proposed LDPC coded strategy to enhance the performance of CVB multiplexing communication systems.