This paper numerically demonstrates synchronization and bidirectional communication without delay line by using two semiconductor lasers with strong mutual injection in a face-to-face configuration. These results show that both of the two lasers＇ outputs synchronize with their input chaotic carriers. In addition, simulations demonstrate that this kind of synchronization can be used to realize bidirectional communications without delay line. Further studies indicate that within a small deviation in message amplitudes of two sides （±6%）, the message can be extracted with signal-noise-ratio more than 10 dB; and the signal-noise-ratio is extremely sensitive to the message rates mismatch of two sides, which may be used as a key of bidirectional communication.
This paper presents a novel approach to extract the periodic signals masked by a chaotic carrier. It verifies that the driven Duffing oscillator is immune to the chaotic carrier and sensitive to certain periodic signals. A preliminary detection scenario illustrates that the frequency and amplitude of the hidden sine wave signal can be extracted from the chaotic carrier by numerical simulation. The obtained results indicate that the hidden messages in chaotic secure communication can be eavesdropped utilizing Duffing oscillators.
We propose a wavelength conversion scheme for chaotic optical communications（COC） based on a Fabry-Perot （FP） laser diode.The FP laser,as a wavelength converter,is injection-locked at one of longitudinal modes by an external continuous-wave（CW） light.The simulation results demonstrated that the chaos masked signal at wavelengthλ_1,which corresponds to the other longitudinal mode of FP laser,can be converted to the injection-locked mode（wavelengthλ_2） based on cross-gain modulation in a closed-loop COC link.A 1.2-GHz chaos masked sinusoidal signal is successfully decoded with signal-to-noise ratio （SNR） beyond 8 dB in 15-nm wavelength conversion range,and the effects of SNR on the signal frequency and conversion span are also investigated.
