Based on chaos synchronization between two 1550 nm response vertical-cavity surface-emitting lasers (R-VCSELs), we propose and numerically investigate a bidirectional dual-channel chaotic secure communication system. Under delayed dual-path chaotic signal injections from the injection VCSEL (I-VCSEL) with polarization-preserved optical feedback, a driving VCSEL (D-VCSEL) can generate an optimized chaotic signal, which can drive two R-VCSELs to output polarization-resolved chaotic signals with wide bandwidth about 35 GHz and low TDS below 0.1 in a relatively large parameter range. Moreover, high-quality isochronal chaos synchronization between the corresponding linear polarization components of two R-VCSELs can be achieved. In contrast, the synchronization quality between D-VCSEL and arbitrary one R-VCSEL is inferior. On this basis, through the polarization-division-multiplexing technique in conjunction with the chaos modulation (CM) method, this proposed system can realize security-enhanced bidirectional dual-channel message transmission of 30 Gbps bipolar non-return-to-zero signals over a 140 km fiber link with Q-factors above six. After adopting four-level pulse amplitude modulation, 60 Gbps signals can be successfully transmitted over a 60 km fiber link with Bit-Error-Rates (BERs) below the hard-decision forward error correction (HD-FEC) threshold of 3.8×10-3.
KEYWORDS: Logic, Signal to noise ratio, Vertical cavity surface emitting lasers, Simulations, Quantum optical ring resonators, Microresonators, Signal intensity, Polarization, Optical resonators, Fire
In this paper, we propose an all optical JK flip-flop system consisting of three vertical-cavity surface-emitting lasers with embedded saturable absorber (VCSEL-SAs) is proposed and numerically simulated. Also, the effects of injection intensity, delay and noise on the JK flip-flop are numerically analyzed. The results show that, based on the spiking dynamics of excited VCSEL-SA, the proposed all-optical JK flip-flop model can perform all the fundamental functions of conventional JK flip-flop under suitable bias current, injection intensity and perturbation delay between two trigger signals. Moreover, the noise has a little effect on the performance of JK flip-flop, but the proposed system has good robustness to the noise. The results provide a feasibility for the application of VCSEL-SA devices in the future ultrafast neuromorphic computing systems.
KEYWORDS: Field programmable gate arrays, Heterodyning, Laser frequency, Digital filtering, Simulink, Process modeling, Feedback control, Tunable filters, Signal generators, Signal filtering
Heterodyne Optical Phase-Locked Loop (HOPLL) is an important technology for laser frequency stabilization. In this work, a digital HOPLL system for realizing frequency offset locking of a Distributed Feedback Semiconductor Laser (DFB-SL) is designed and implemented. The system is composed of a Frequency Synthesizer (FS), a passive third-order loop filter and an adjustable gain module. The effectiveness of the system is tested by measuring the frequency offset locking of DFB-SL. The results show that the designed system provides a cost-effective, sensitive, and reliable way to lock the DFB-SL with suitable parameters, and the drift caused by environmental variations can be suppressed effectively.
We experimentally investigated multi-channel chaos synchronization characteristics based on two asymmetrical mutually coupled Weak-Resonant-Cavity Fabry-Perot Laser Diodes (WRC-FPLDs). Experimental results show that, through adjusting the center wavelength of the Tunable Optical Filter (TOF) and the injection power, different modes can be selected and induced into chaotic state with wideband. Under proper asymmetrical injection power and frequency detuning, stable leader-laggard chaos synchronization with the maximal correlation coefficient about 0.90 between two asymmetrical mutually coupled WRC-FPLDs can be achieved. In addition, the effects of injection power and frequency detuning between the two lasers on chaos synchronization performance have also been discussed.
Based on a vertical-cavity surface-emitting laser with saturated absorber (VCSEL-SA) subject to optical injection, we proposed an ultrafast pattern recognition scheme of four-bit binary data and theoretically investigated the recognition performances. The results show that, patterns recognition of different four-bit binary data at Gb/s rate can be realized by adjusting the injection weight of each bit number and optimal weight values can be determined. Although noise has some influences on the patterns recognition speed and accuracy, this proposed system has a certain robustness to noise on the whole. These results provide a promising application prospect for VCSEL-SA based ultrafast photonic neuromorphic system in pattern recognition field.
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