Coherent secure communication based on optical intensity-modulation injected semiconductor lasers

In this paper, we propose a coherent chaotic communication scheme based on optical chaos generated by a semiconductor laser subject to intensity-modulated injection, where the chaos has no time delay signature, which intrinsically exists in the widely adopted external-cavity laser configuration. The generated chaos is employed to drive and synchronize two slave lasers. The experimental results demonstrate that optical chaos with a bandwidth of more than 28 GHz can be obtained and synchronized with high quality. The scheme features a relatively low cost since it does not require RF signal generators with extremely high frequencies for broadband chaos generation. Then, secure communication of 25 Gb/s quadrature phase-shift keying signals is achieved after transmission over 80 km of standard single-mode fiber. Furthermore, the security and sensitivity are evaluated by analyzing the bit error ratio versus the system parameters such as the masking coefficient and the received power.