Fractional Fourier Transform Dual Random Phase Encoding of Time-Varying Signals

CUADRADO LABORDE, CHRISTIAN; DUCHOWICZ, RICARDO; TORROBA, ROBERTO; SICRE, ENRIQUE

OPTICS COMMUNICATIONS

Elsevier

Lugar: Amsterdam; Año: 2008 vol. 281 p. 4321 - 4328

0030-4018

Optical techniques have shown great potential in the field of information security to encode high-security images. Among several established methods, a double-random phase encryption technique (DRPE) for encoding a primary image into stationary white noise was developed by using the analogy between Fresnel diffraction patterns and the fractional Fourier transform (FrFT-DRPE). In this case, additional keys are obtained through the knowledge of the fractional orders of the FrFTs. In this work we propose an encoding setup for time-varying signals, mainly for short-haul fiber optics link applications, that can be considered as the temporal analogue of the spatial FrFT-DRPE. The behavior of the proposed method is analyzed by employing the Wigner distribution function. As a result, general expressions for both signal time width and spectral bandwidth, at all encryption stages are obtained. Numerical simulations have beencarried out to illustrate the system performance. The obtained results indicate that this encryptionmethod could be a good alternative to other well-established methods.