Abstract

In this article, a three-dimensional sparse code division multiple access (SCMA) orthogonal frequency division multiplexing (OFDM) passive optical network (PON) high-security optical transmission system based on a random codebook is proposed. The system can achieve a 150% overload of access users and secure user information through chaotic encryption on the physical layer. The encryption method includes random codebooks, encrypted constellations, and encrypted frequency domain symbols. In addition, a 3D codebook design method is proposed in this article. The 3D-SCMA-OFDM signal transmission of 8.86 Gb/s is experimentally verified on a 2 km 7-core fiber. The receiver sensitivity gain of 3D-SCMA-OFDM is 3 dB compared to conventional 2D-SCMA-OFDM. This is achieved at a bit error rate of 3.8 × 10^-3 for hard decision forward error correction (HD-FEC). In addition, the complexity of the 3D-SCMA-OFDM receiver-side decoding algorithm is 86.36% lower than that of the conventional 2D-SCMA-OFDM. The reduction in complexity dramatically improves the responsiveness of the system. The key space of this encryption method is 10¹⁶⁵, which can strongly resist illegal reception. The results show that the 3D-SCMA-OFDM PON high-security optical transmission system proposed in this article has many points: extensive user access, good transmission performance, fast response speed, and high security. It has a broad application prospect in the future optical access network.