Three-dimensional spherical signal constellation for few-mode fiber based high-speed optical transmission

We propose the optimized three-dimensional spherical signal constellations (3D-SSCs), suitable for use in few-mode fiber-optic communications. The proposed signal constellations are based on the optimum distributions, which are determined by the split-step method. The numerical results show that the 3D-SSCs outperform the previously proposed constellations and improve the optical signal-to-noise ratio sensitivity by up to 3.89dB at bit error ratio of 10^-6.