Narrowband information encryption using frequency and phase cipher

In this paper, we propose a method for optical communication encryption, based on multi-sub carriers modulation, reducing the transmitted signal effectively below the noise level. The information reconstruction is possible only if the frequencies of the carriers, the phase distortion, and the sampling frequency at the transmitter are in hand. Sampling the signal before transmission improves the SNR after reconstruction, enabling to transmit a low power signal with a low SNR which results in a stealthy transmission.