LAUSR

In this paper, a novel three-dimensional constellation diagram is proposed for optimizing the spatial coordinates of constellation points using geometric shaping (GS), which improves the constellation figure of merit (CFM) and, as a result, reduces the bit error rate (BER). A three-dimensional carrier-free amplitude phase (CAP) modulated signal transmission at 25.45Gb/s is successfully implemented on a seven-core fiber communication system to verify the performance of the constellation diagram. Compared to the traditional scheme, this method has an average receiver sensitivity gain of 1.4dB at BER ∼1 × 10-3, further, the receiver sensitivity gain difference of 1.3dB between different cores. The experimental results show that this scheme effectively reduces BER without additional communication components, which can be used in short-distance access networks in the near future.