Optical chaotic communication using correlation demodulation between two synchronized chaos lasers

Abstract This paper theoretically investigates the scheme of optical chaotic communication based on correlation demodulation between two synchronized semiconductor lasers. In the scheme, a semiconductor laser (SL) system, which is subject to phase conjugation and electro-optical phase modulation feedback, generates optical chaos with high-complexity, simultaneously, the time-delay (TD) signature can be well concealed. We use the digital signal “0” and “1” to control the chaotic signal’s switching between two arms of electro-optical (E-O) switch to indirectly achieve spreading spectrum. Concretely, for the “0” bit, at the cross arm the waveform of the optical chaotic signal is reversed by utilizing the cross gain modulation (XGM) effect of semiconductor optical amplifier (SOA); for the “1” bit, the chaotic signal is exchanged from the cross arm into the through arm. Based on the four-wave mixing (FWM) effect of optical parameter amplifier (OPA), the optical chaotic signal is converted to the same center wavelength as SOA’s output, and then two chaotic sequences are coupled into a channel in turn, as a results, the power of the signal of 5 Gbit/s is uniformly distributed and expanded to about 23.45 GHz bandwidth, thus its power spectrum density (PSD) becomes very low. We numerically demonstrate that this chaotic dynamics between the transmitter and the receiver can be identically synchronized due to coupling. The results indicate that the novel correlation-demodulation-based optical chaotic communication scheme can tolerate a higher noise level, and it can achieve a high-quality communication under lower signal-to-noise ratio (SNR). Compared with the scheme of synchronized error monitor, the correlation demodulation way has better ability for anti-noise interference.