High-security multi-level constellation shaping trellis-coded modulation method based on clustering mapping rules.

This paper proposes a high-security multi-level constellation shaping trellis-coded modulation (TCM) method based on clustering mapping rules, which is suitable for passive optical networks (PON) using three-dimensional (3D) carrier-less amplitude and phase modulation (CAP). This method combines the TCM mapping process with the constellation shaping and performs a multi-level mapping of the coded signal according to the classification label, so as to obtain better constellation shaping gain while expanding the coding gain of the TCM. The 3D constellation generated by the multi-level mapping adopts Chua's chaotic model for rotation encryption, which improves the ability of the optical access network to resist malicious attacks at the physical layer. Experiments show that 70 Gb/s (7×10 Gb/s) transmission is achieved on a 2 km weakly coupled seven-core fiber using the scheme proposed in this paper. At a bit error rate (BER) of 1 × 10-3, the difference in receiver sensitivity between the best and worst-performing cores is about 0.7 dB. The difference in receiver sensitivity between the cubic constellation and the chaotic spherical constellation is about 0.1 dB. The sensitivity of the chaotic spherical constellation receiver is about 6.98 dB higher than that of the 2D shaping constellation receiver. The experimental results show that the scheme has reliable security performance while improving the short-reach transmission capacity. It has broad application prospects in future short-reach communication research.