Wavelength division multiplexing secure communication scheme based on an optically coupled phase chaos system and PM-to-IM conversion mechanism

We propose a wavelength division multiplexing secure communication scheme based on an optically coupled phase chaos system and phase modulation to intensity modulation (PM-to-IM) conversion mechanism. In this scheme, three channels of intensity-modulated data signal are simultaneously distorted by chaotic phase noise. Dispersion-induced PM-to-IM conversion mechanism is used to mask the data signal in intensity dimension. An additional self-phase modulation feedback loop in each channel is used to further scramble the phase dimension, and a time-domain key is introduced by a fiber delay line. The numerical results indicate the good encryption and decryption performance as the fundamental communication characteristics. The wavelength spacing under different parameter settings is also investigated in the wavelength division multiplexing scenario. Moreover, time delay signature concealment is confirmed by using both autocorrelation function and delayed mutual information approaches. Finally, the sensitivity dependence on key parameters and robustness of the scheme are discussed in detail. Both the security and feasibility can be guaranteed. The scheme has the potential to be used in large capacity optical secure transmission systems.