Secure OCDM Mode Division Multiplexed Short-Reach Optical Communication Based on Time-Frequency Joint Perturbation

A secure orthogonal chirp division multiplexing (OCDM) mode division multiplexed (MDM) short-reach optical communication based on time-frequency joint perturbation is proposed in this paper. Firstly, the discrete Fresnel transform (DFnT) was used to realize the digital realization of OCDM, and then the Lorenz chaos model and Logistic chaos model were combined to realize the time-frequency perturbation of the orthogonal chirped subcarriers and chirped symbols. The digital up-conversion (DUC) was used to transform the OCDM signal and transmit it in the MDM short-reach optical communication system. The chirped signal has good pulse compression and spread spectrum capability, the maximum chirped spread spectrum can be achieved by using OCDM based on DFnT. The time-frequency joint perturbation of the double chaos model can achieve a large keyspace of $1{\bf } \times {\bf }{10^{144}}$ and improve the security of information transmission. DUC technology can transform OCDM signal from complex to a real number, which can meet the transmission requirements of the MDM IM/DD system and increase the transmission spectrum efficiency. Through experiments, 32Gb /s OCDM encrypted signal transmission is realized across 5km few-mode fiber, the OCDM has a maximum receiver sensitivity gain of 1.48 dB compared with OFDM at $1{\bf } \times {\bf }{10^{ - 2}}$ bit error rate. The results show that the proposed secure OCDM-MDM short-reach optical communication scheme based on time-frequency joint perturbation has good anti-interference and security performance, as well as a wide range of applications in the future short-reach optical communication.