Performance and Security Improvement of Three-Dimensional Orthogonal Chirp Division Multiplexing System With 2D-IDFnT

In this article, an improved scheme of orthogonal chirp multiplexing (OCDM) system for the passive optical network (PON) is proposed, which adopts a three-dimensional (3D) constellation and two-dimensional inverse discrete Fresnel transform (2D-IDFnT). The 3D constellation and the chirp signal in the time domain are encrypted by 6D Duffing-Lu chaotic system. Transmission of 10.3 Gb/s encrypted 3D-OCDM signal is successfully demonstrated on 2 km 7-core fiber. Compare 3D-OCDM with 2D-OCDM and 3D-OFDM, the transmission performance of the proposed 3D-OCDM scheme is much higher than them. When the bit error rate of hard decision forward error correction is 3.8 × 10-3, 3D-OCDM achieves sensitivity gains of 1.5 dB and 2.0 dB, respectively. Finally, the experimental results show that the proposed encryption scheme's key space is 10
²⁰⁸
, enough to resist hijackers and attacks from illegal receivers.