Three-Dimensional Probabilistically Shaped CAP Modulation Based on Constellation Design Using Regular Tetrahedron Cells

This article proposes a novel 3-D probabilistically shaped carrier-less amplitude phase (3D-PS-CAP) modulation based on constellation design using regular tetrahedron cells, which is capable of being applied in short reach communication. Geometric shaping based on regular tetrahedron cells for 3D constellation, combined with probabilistic shaping, can increase the constellation figure of merit (CFM) of the 3D constellation and improve the bit error rate (BER) performance of the 3D-PS-CAP modulation scheme. An experiment demonstrating 4 Gb/s 3D-PS-CAP-16 data transmission over 25 km standard single-mode fiber (SSMF) is successfully carried out. Results show that at the BER of \text{1} \times \text{10}^{ -\text{3}}, the proposed uniform 3D-CAP-16 outperforms the traditional counterparts by 1.1 dB receiver sensitivity gain. Moreover, in the entropy of 3.6 bits/symbol, the proposed 3D-PS-CAP-16 obtains 0.6 and 1.0 dB receiver sensitivity gains compared to the two traditional 3D-PS-CAP-16, respectively. The experimental results indicate the proposed scheme a bright prospect for future short reach communication.