Parallel generation of low-correlation wideband complex chaotic signals using CW laser and external-cavity laser with self-phase-modulated injection

Abstract

A novel scheme for generating optical chaos is proposed and experimentally demonstrated, which supports to simultaneously produce two low-correlation chaotic signals with wideband spectrum and suppressed time-delay-signature (TDS). In the proposed scheme, we use the output of an external-cavity semiconductor laser (ECSL) as the driving signal of a phase modulator to modulate the output of a CW laser. Then the phase-modulated continuous-wave (CW) light is split into two parts, one is injected back into the ECSL that outputs one chaotic signal, while the other part is passed through a dispersion module for generating another chaotic signal simultaneously. The experimental results prove that the proposed scheme has three merits. Firstly, it can improve the bandwidth of ECSL-based chaos by several times, and simultaneously generate another wideband flat-spectrum chaotic signal. Secondly, the undesired TDS characteristics of the simultaneously-generated chaotic signals can be efficiently suppressed to an indistinguishable level within a wide parameter range, as such the complexities of the chaotic signals are considerably high. Thirdly, the correlation coefficient between these two simultaneously-generated chaotic signals is smaller than 0.1. The proposed scheme provides an attractive solution for parallel multiple chaos generation, and shows great potential for multiple channel chaos communications and multiple random bit generations.