Time-variant signal encryption by lensless dual random phase encoding applied to fiber optic links.

A lensless dual random phase encoding technique in the temporal domain is proposed and analyzed to evaluate its potential application for secure data transmission, mainly for short-haul fiber optic links. The different signal broadening effects produced by each stage of the encoding process in both time and frequency domains are analyzed by using the Wigner distribution function to take into account the fiber's multiplexing capabilities. Thus, quasi-white noise with a well-defined bandwidth is used in the encoding process to limit the bandwidth of the encrypted signal. Numerical simulations revealed good system performance, indicating that this multiplexing encryption method could be a good alternative to other well-established techniques.