Generation of synchronized wideband complex signals and its application in secure optical communication

We propose and demonstrate a novel secure optical communication scheme, in which the message signal is encrypted and decrypted by two synchronized wideband complex signals. In our scheme, the wideband complex signals are generated by two private chaotic driving signals which are obtained from two local conventional external-cavity semiconductor lasers (ECSLs) subject to a common injection. Both the experimental and simulation results show that, the effective bandwidths of the chaotic driving signals are significantly improved and the time-delay signatures are completely suppressed, in virtue of the spectral broadening effect of chaotic phase-modulation and the phase-to-intensity conversion effect of dispersive components. Furthermore, the generated wideband complex signals are used as the optical carriers for achieving secure transmission. The message signal with a bit rate up to 10 Gb/s can be well hidden into the carrier, and cannot be recognized by the eavesdropper. The high-quality synchronization ensures that the message signal can be correctly recovered at the receiver.