Enhancement of chaotic carrier bandwidth in a semiconductor laser transmitter using self-phase modulation in an optical fiber external round cavity

A novel method to enhance the bandwidth of a chaotic carrier from a delayed feedback semiconductor laser transmitter is pre- sented using self-phase modulation (SPM) in an optical fiber external round cavity. A physical model of the laser dynamics is established under the condition of optical feedback light with the SPM effect in the fiber path. A formula for frequency detuning of the optical dual-feedback under SPM is theoretically deduced. The results show that the nonlinear phase shift caused by SPM has an impact on the gain and bandwidth enhancement factor of the laser. The second-order nonlinear effect of the fiber enriches the variety of the amplitudes and phases of the laser while the nonlinear phase shift produces a number of new frequencies, which can spread the bandwidth. Numerical results reveal that with the SPM effect, the bandwidth can be enhanced 4 times more than the bandwidth without it, and the relaxation oscillation frequency of the chaotic laser is increased to 2.56 times more than that of the laser without the fiber path. The enhancement of the chaotic bandwidth can be extended by increasing the optical fiber length, the coupling-feedback ratio, the mirror reflectance and the second order nonlinear coefficient affect.

Control of chaos in an external-cavity multi-quantum-well laser subjected to dual-wedges and optical dual-feedback

A multi-parameter chaos-control method used to control chaos in an external cavity multi-quantum-well (MQW) laser via the dual-wedges and external delayed optical dual-feedback is presented. The physical model of the laser dynamic is established under the conditions of the dual-wedges and dual-feedback light control. The frequency detuning and stable ranges of the control system are theoretically demon-strated. The optical-length of the feedback light may be adjusted by shifting horizontally or sliding the dual-wedges relatively in the external optical road, which will alter the delaying time and feedback in-tensity of the dual-feedback light. Accordingly, the multi-parameter chaos-control of the optical dual-feedback may be achieved physically. The numerical simulations approve that the chaotic laser may be controlled into a stable state, a single-periodic state and multi-periodic states, and the con-trolled periodic pulse power may be increased.

Chaotic laser synchronization and its application in optical fiber secure communication

In this paper, optical fiber chaotic secure communication is proposed bycoupling chaotic laser synchronous system with optical fiber propagation channel.Feedback synchronous system of chaotic semiconductor lasers is presented andsynchronous error and decoding formulae are demonstrated. Synchronization betweentwo chaotic laser systems with distributed feedback semiconductor lasers at wavelengthof 1.31 μm is simulatively achieved with almost zero synchronous error. Parametermismatch, synchronous transient response and noise effect on the system are studied.Robustness of synchronization and anti-perturbation can increase by increasing thefeedback coefficient of the system. Influence of group-velocity-dispersion and self-phasemodulation of optical fiber on chaotic laser signal and synchronization are analyzed, and itis found that group-velocity-dispersion affects pulse shape, synchronization and decoding,and limits optical fiber propagation distances, and self-phase modulation does not affectpulse shape, while its product of nonlinear phase shift can affect synchronization anddecoding, and restrict propagation distances of optical fiber chaotic communicationsystem and hence the maximum optical power formula is educed. Injecting parametermodulation and amplitude modulation are numerically simulated in long-haul optical fibersecure communication systems.