Steganographic fiber-optic transmission using coherent spectral-phase-encoded optical CDMA

Spread spectrum (SS) has been used extensively in military radio communications to ensure low probability of intercept of a transmitted signal by an unintended receiver. Low probability of intercept is achieved using a unique code to spread the transmitted signal into noise-like signal having low spectral power density. The SS signal is submerged below the background noise, making it difficult to be detected by a hostile eavesdropper. Low probability of intercept is ensured because the original signal can only be recovered if the receiver knows the spreading code. The application of SS techniques in radio frequency wireless communications has been widely implemented using code-division multiple-access (CDMA), which provides both high spectral efficiency and steganographic security, , where only an authorized user knows of the existence of the secret message.