Three-dimensional non-orthogonal multiple access high-security seven-core transmission system based on constellation chaotic selection mapping

This paper proposes a three-dimensional non-orthogonal multiple access (3D-NOMA) high-security transmission in a seven-core fiber based on chaotic selection mapping of constellations. The transmission scheme uses a four-dimensional hyperchaotic model for the first selection mapping mask and the second selection mapping mask for 3D constellation points. The first selection mapping mask randomly permutes the information of each mapped constellation point to complete the first layer of encryption. The second selection mapping mask maps the constellation points onto the hollow sphere domain in 3D space through encrypted data preprocessing mapping rules to complete the second layer of encryption. The joint mapping of two-layer encryption provides greater security and flexibility for constellation encryption. An ample key space∼10 ¹⁵⁰ with an effective information transmission of 35.51 Gb/s was demonstrated experimentally in a 2 km 7-core fiber. The 3D orthogonal frequency division multiplexing (3D-OFDM) is transmitted simultaneously under the same conditions, and compared with 3D-OFDM, the proposed 3D-NOMA scheme could potentially expand the number of users without obvious performance degradation. The experimental results show that the scheme can effectively protect the system from illegal optical network unit attacks and is ideal for physically securing 3D-NOMA in the future.