Flat broadband chaotic carrier generation and synchronization

The chaotic carrier with smooth spectrum and broad bandwidth is generated by a distributed feedback （DFB） semiconductor laser subject to unidirectional fiber ring optical feedback. The smooth spectrum of the obtained chaotic carrier hides the external cavity resonance frequency peak，therefore the security of the system is enhanced. By unidirectional coupling，we implement the stable chaos synchronization when the chaotic light is injected into a solitary DFB laser diode. The correlation coefficient of synchronization is 0.84. The effects of injection strength and optical frequency detuning on synchronization are investigated experimentally. The results show that in conditions of strong injected locking the synchronization can be achieved in a large range of frequency detuning，and the stronger injection corresponds to the larger range of frequency detuning in which chaos synchronization maintains. The synchronization quality improves with the injection strength increasing.