A method for providing spectral and temporal stealthy information transmitted over an optical communication channel, according to which, at the transmitting side, the power spectral density of a pulse sequence bearing the information is reduced by encrypting the temporal phase of the pulse sequence. The power of the pulse sequence is spread in the frequency domain, to be below the noise level, by sampling the pulse sequence. Spectral phase encoding is used to temporally spread the pulse sequence and to prevent coherent addition of its spectral replicas in frequency domain. The resulting signal, encrypted both in time and frequency domains, is then transmitted. Spectral phase decoding is performed at the receiving side by performing coherent detection and folding all the spectral replicas of the transmitted signal to the baseband by means of sampling. The temporal phase of the signal is decrypted and the information which is delivered by the pulse sequence is decoded.
|US patent No. 9288045
|Published - 2011