Contents I. Introduction
Along with the development of optical telecommunications systems has come an interest in secure optical transmissions and in optoelectronics techniques for signal encryption. Several optoelectronics systems have been proposed that exploit fast chaotic dynamics as a possible alternative to classical encryption techniques based on numerical algorithms. The first schemes proposed relied on signal masking: a small amplitude information signal is hidden by a large-amplitude noise-like chaotic signal. Optical systems have been reported theoretically [1], [2] and experimentally from Nd : YAG lasers [3], erbium-doped fiber lasers [4] [5] [6] [7], and semiconductor lasers [8] [9] [10] [11] [12]. With such schemes, signal encoding is performed through the continuous modulation of a dynamical variable of a chaotic oscillator; decoding is achieved by synchronizing a chaotic receiver to the chaotic transmitter.
