Performance and security improvement of three-dimensional orthogonal chirp division multiplexing system with 2D-IDFnT

In this paper, 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 10.3Gb/s encrypted 3D-OCDM signal is successfully demonstrated on 2km 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 10208, enough to resist hijackers and attacks from illegal receivers.