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.
Based on two Response Vertical-Cavity Surface-Emitting Lasers (R-VCSELs) subject to identical chaos optical injection with phase modulation and dispersion compensation, we propose and numerically investigate a high-speed bidirectional chaotic secure communication system. The driving VCSEL (D-VCSEL) is used to generate the injected chaotic signals to two R-VCSELs. After introducing the phase modulation and dispersion compensation into injection path, the bandwidth of chaotic carrier from the linear polarization components of R-VCSEL1 and R-VCSEL2 can be extended to 45GHz, and corresponding Time Delay Signatures (TDSs) can be suppressed to about 0.15. Moreover, high-quality chaos synchronization between corresponding polarization components of two R-VCSELs but very low correlation between the D-VCSEL and any R-VCSEL can be achieved. On this basis, the bidirectional dual-channel information transmission of 30 Gbit/s over 100 km fiber link is successfully realized.
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.
We proposed a reconfigurable all-optical logic gate (AND, OR) based on a vertical-cavity surface-emitting laser with saturated absorber (VCSEL-SA) subject to dual pulse injection and numerically investigated the effects of injection delay, injection strength and bias current on the system performance. The results show that, through adjusting bias current, the pulse injection strength and the injection delay between two pulses, the reconfigurable all-optical logic gate (AND, OR) can be realized. For a suitable injection intensity, all-optical logic AND and OR gates can be implemented within a certain bias current range. Moreover, both AND and OR gates have good robust to noise under suitable injection strength. These results are expected to open a new window for future ultra-fast neuromorphic computing systems to solve complex classification and decision-making tasks
In this paper, we propose and numerically demonstrate a security-enhanced high-speed chaotic communication system by introducing phase modulation and phase-to-intensity conversion. The driving laser (DL) with delayed optical feedback can be used to generate the chaotic driving signal, which is simultaneously injected into two response lasers (RLs) through a phase modulator (PM) and a dispersion component (De). The simulated results show that, due to the phase modulation and phase-tointensity conversion, TDS of injected chaos signal from DL can be effectively suppressed and its bandwidth can be increased to 39.6 GHz under suitable parameter conditions. Simultaneously injecting the chaos signal into two identical RLs, high-quality chaos signals with weakened TDS and enhanced bandwidth between two RLs can be achieved even under certain parameter mismatches, but the synchronization quality between DL and any one of RLs is extremely bad. Based on the system synchronization, secure transmission of 20 Gbit/s messages can be realized and the transmission distance can be over 200km.
Based on a slave vertical-cavity surface-emitting laser (S-VCSEL) simultaneously driven by dual chaotic optical injection (DCOI) from two master VCSELs (M-VCSELs) with double optical feedback (DOF), an unpredictability-enhanced broadband chaotic signal generation scheme is proposed and numerically investigated. The unpredictability degree (UD) and bandwidth of chaotic signals are evaluated by the peak value (σ) of self-correlation function (SF) at the feedback time and the effective bandwidth (EBW), respectively. The results show that, M-VCSEL with DOF can generate chaos signals with lower time delay signature (TDS) than that with single optical feedback (SOF). Under suitable injection strength and frequency detuning, both two orthogonal polarization components (X-PC and Y-PC) of the S-VCSEL can be driven to generate unpredictability-enhanced broadband chaotic signals with suppressed TDS (σ < 0.1) and wide EBW (EBW < 50GHz). Moreover, a relatively large parameter space to achieve this high-quality chaos signals can be determined.
Based on vertical-cavity surface-emitting lasers (VCSELs) with optical injection and polarization-rotated optical feedback, we propose and numerically demonstrate a scheme for generating synchronized random bit sequences (SRBS) for two legal users at different locations. For the scheme, the chaotic signal generated by a driving VCSEL (D-VCSEL) subject to chaotic optical injection are utilized to simultaneously drive two VCSELs (A-VCSEL and B-VCSEL) with polarization-rotated feedback, then the chaotic outputs from A (B)-VCSEL are used as physical entropy sources to generate SRBS. The simulated results show that, the SRBS at a rate up to 400 Gbits/s can be achieved after adopting suitable post-processing method. The security of this scheme can be ensured by a high-quality synchronization between A-VCSEL and B-VCSEL while relatively low-quality synchronization between D-VCSEL and A (B)-VCSEL. Moreover, the BER and the randomness of generated SRBS are also discussed.
We theoretically investigate the propagation characteristics of inhibited spiking dynamics between two unidirectionally coupled VCSEL-based photonic neurons. The results show that, the inhibition of spiking regimes in a transmitter VCSEL (T-VCSEL), in response to the arrival of external perturbation, can be propagated to another receiver VCSEL (R-VCSEL) and two VCSEL-based photonic neurons have similar responses to the external perturbation. With increasing perturbation strength, the spikes with higher amplitude and lower oscillation frequency can be observed during the perturbation time. The spikes can be entirely suppressed for enough perturbation strength. Additionally, the spiking inhibition window can be controlled through adjusting perturbation duration.
Under suitable filtered optical feedback, a weak-resonant cavity Fabray-Perot laser diode (WRC-FPLD) is rendered into chaotic state, and the central wavelength of chaotic output can be tuned through varying the central wavelength of filter. The output chaotic signal with wavelength-tunability is unidirectionally injected into another WRC-FPLD and drives it into chaotic state, and then wavelength-tunability chaos synchronization can be realized. The experimental results demonstrate that, under suitable injection strength and frequency detuning, chaos synchronization between two unidirectionally coupled WRC-FPLDs with maximal correlation coefficient about 0.900 can be achieved under different wavelengths.
A bandwidth-enhanced chaos synchronization communication system is proposed and its communication performance is investigated numerically. The results show that, using a bandwidth-enhanced chaotic signal from a driving vertical cavity surface-emitting laser (D-VCSEL) to drive two mutually coupled VCSELs (MC-VCSELs), the high-quality isochronal chaos synchronization with over 30GHz bandwidth between two corresponding LP modes in the two MCVCSELs can be obtained. Taking two LP modes as two different communication channels and adopting chaos masking (CMS) encryption scheme, this system can realize the bidirectional dual-channel high-speed chaos communication at 10Gbits/s transmission rate. Moreover, the parameters mismatches tolerance of this communication system and the influence of message transmission rate on the communication performance also are discussed.
A bidirectional chaos communication system, composed of 1550nm semiconductor lasers (SLs) and fiber links, is
experimentally and numerically investigated. Based on the robust chaos synchronization between two authorized SLs,
0.5Gbits/s pseudo-random data bidirectional message transmission between the two SLs has been preliminarily realized
experimentally. Moreover, related theoretical simulations are also given, which basically conforms to our experimental
observations.
We experimentally and numerically investigate the chaos synchronization characteristics of mutually coupled system
consisted of two semiconductor lasers (SLs) with asymmetrical bias currents. The results show that, for the case of the
two SLs with identical free running oscillation frequencies, the mutually coupled system can achieve excellent chaos
synchronization under relatively large asymmetrical bias currents. Frequency detuning Δ (Δ=1-2, where 1, 2 are the
free running frequencies of SL1 and SL2, respectively) has obvious influence on the synchronization performance. For
the case of the SL1 biased at a relatively much larger current compared with that of SL2, the synchronization
performance will be degraded with the increase of the positive frequency detuning (1>2), while the synchronization
performance can be further improved with suitable negative frequency detuning. The simulated results are basically
consistent with experimental results.
In this paper, the total output power features and the mode power characteristics of the extremely short external cavity
semiconductor lasers (ESECSLs) have been investigated experimentally and theoretically, and a new type of variation of
ESECSL's mode power is reported. The results show that with the variation of the external cavity length at the order of
lasing wavelength, the total output power and the mode power of ESECSLs will hop periodically, and the different mode
presents diverse power characteristics. Especially, some modes, locating at the material gain center of ESECSL, present
unique double peak characteristics. Moreover, the primarily theoretical simulations and the physics explanation about
these double peak characteristics have been given. The theoretical simulation results agree well with the experimental
results. These new type characteristics of ESECSL's mode power may be useful in improving the sensitivity of all-optical
sensors and developing the new type of optical data read-write head.
In this paper, after taking into account two situations that the polarization of the injection light is parallel or orthogonal
with the solitary vertical-cavity surface-emitting laser (VCSEL) output light, the nonlinear dynamic characteristics of an
optical injection VCSEL are investigated numerically. The simulated results show that VCSEL can exhibit periodic
oscillations, deterministic chaos and other complex instabilities under optical injection. For parallel or orthogonal optical
injection, the same injection coefficients have different effects on the output of VCSEL. By properly adjusting the
injection strength or detuning frequency, the dynamical state of the laser output can be controlled to a fixed state, and the
polarization of the VCSEL output light can also be controlled.
After taking into account the multiple reflections of light in external cavity, the influence of the optical feedback on the large signal modulation characteristics of the external cavity semiconductor laser (ECSL) has been theoretically investigated. The numerical simulations show that, with the increase of the modulation index, the peak photon number of the ECSL tends to higer level on the whole. When the optical feedback is strong or weak, the peak photon number of the ECSL shows single period. However, the peak photon number exhibits bifurcation or chaos for different modulation index when the optical feedback is intermediate.
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