Generation Of Wideband Chaos Research Articles

Wideband chaos generation using a VCSEL with intensity modulation optical injection for random number generation

Wideband chaos generation using a VCSEL with intensity modulation optical injection for random number generation

Generation of Wideband Chaos With Time-Delay Signature Suppression in Semiconductor Lasers by Asymmetrical Mutual Injection

Generation of Wideband Chaos With Time-Delay Signature Suppression in Semiconductor Lasers by Asymmetrical Mutual Injection

Generation of Wideband Chaos Without Time-Delay Signature via Cascaded Chirped Fiber Bragg Grating Feedback

Generation of Wideband Chaos Without Time-Delay Signature via Cascaded Chirped Fiber Bragg Grating Feedback

Generation of wideband chaos without time delay signature using the microlaser with dispersive optical feedback

We propose and numerically demonstrate a method of generating wideband chaos laser without time delay signature by using a circular-side hexagonal resonator (CSHR) microlaser with optical feedback from a chirped fiber Bragg grating (CFBG). The theoretical model of the circular-side hexagonal resonator microlaser with chirped fiber Bragg grating feedback is established according to the Lang-Kobayashi equations. The effects of bias current, feedback strength and CFBG dispersion on the bandwidth of the chaos laser and the feedback time delay signature are investigated. The results show that the CFBG-feedback CSHR microlaser can generate a wideband chaos without feedback time-delay signature under the condition of high bias current with a wideband and flat small-signal modulation response and the bandwidth can reach 14 GHz.

Wideband chaos generation based on a dual-mode microsquare laser with optical feedback

We propose and demonstrate the generation of wideband chaos based on a dual-mode microsquare semiconductor laser with optical feedback. By adjusting the dual-mode intensity ratio and the feedback strength, wideband chaos covering more than 50 GHz in the RF spectrum is achieved. The standard and effective bandwidths of the chaotic signal are 31.3 GHz and 30.7 GHz with the flatness of 8.3 dB and 6.1 dB, respectively.

Generation and synchronization of wideband chaos in semiconductor lasers subject to constant-amplitude self-phase-modulated optical injection.

We propose a novel wideband chaos generation scheme by using an external-cavity semiconductor laser (ECSL) subject to optical-electronic hybrid feedback. In this scheme, the output of ECSL is photo-detected and used to modulate the output of a continuous wave laser by an electro-optical phase modulator, the constant-amplitude self-phase-modulated light is then injected back into the ECSL. The experimental results indicate that, compared with the chaos generation with conventional optical feedback (COF), significant bandwidth enhancement is achieved in the proposed scheme. The effective bandwidth of generated chaos is increased from a few GHz to over 20 GHz, and moreover, the spectrum flatness and the complexity of generated chaos are also considerably improved. Furthermore, we propose a wideband chaos synchronization system based on the proposed chaos generation scheme. It is experimentally demonstrated that high-quality synchronization between two wideband chaos signals with an effective bandwidth greater than 20 GHz is achieved. This work simultaneously achieves the generation and the synchronization of wideband chaos, which shows valuable potential in chaos-based secure communication, such as enhancing the transmission capacity and improving the security.

Wideband Time Delay Signature-Suppressed Chaos Generation Using Self-Phase-Modulated Feedback Semiconductor Laser Cascaded With Dispersive Component

We propose a wideband chaos generation scheme that shows significant bandwidth enhancement and excellent time delay signature (TDS) suppression, by introducing self-phase modulation in the feedback loop of external-cavity semiconductor laser (ECSL) and passing the ECSL-generated chaos through a dispersive component. Proof-of-concept experiment and thorough complementary numerical simulations are carried out to study the efficient bandwidth and TDS characteristics of the generated chaos. The results demonstrate that with the joint contributions of self-phase modulation and dispersion, the efficient bandwidth of chaos can be enhanced by several times and the spectrum gets much flatter. Simultaneously, the TDS can be completely suppressed, in a wide operation parameter range. The proposed wideband chaos generation scheme shows great potential for the applications of fast random bit generation, high-resolution chaotic radar, and high-speed chaos communication.

Chaotic optical communications over 100-km fiber transmission at 30-Gb/s bit rate

For the first time, to the best of our knowledge, we experimentally demonstrate a successful 30-Gb/s signal transmission of a duobinary message hidden in a chaotic optical carrier over 100-km fiber. Thanks to the duobinary modulation format with high spectral efficiency, the 30-Gb/s signal can be encrypted by a 10-GHz-wide chaotic carrier. A digital signal processing technique can be used to convert duobinary data into binary data on the receiver side. This proposal lowers the requirement for wideband chaos generation and synchronization in high-speed long-distance chaotic optical communications, and fiber dispersion compensation can also be simplified, which has potential to be used in high-speed long-distance secure optical communications.

Passive Chaos Bandwidth Enhancement Under Dual-Optical Feedback with Hybrid III–V/Si DFB Laser

The chaotic dynamics of a DFB laser are studied experimentally under a combination of short and long feedbacks. Chaos bandwidth enhancement is demonstrated using a hybrid III–V/Si DFB laser with a large relaxation oscillation frequency (ROF) of 14 GHz. The impact of short feedback on the ROF is studied and an increase of 2 GHz is observed. Under long feedback, the route to chaos of the device and its dependence on the short feedback dynamics are studied. The short feedback allows tuning the chaotic dynamics obtained under long feedback, and the increase of the ROF translates into an enhancement of the chaos bandwidth to above 16 GHz. This configuration can allow generation of wideband chaos using a single laser source in a photonic integrated circuit.

Generation of flat wideband chaos with suppressed time delay signature by using optical time lens.

We propose a flat wideband chaos generation scheme that shows excellent time delay signature suppression effect, by injecting the chaotic output of general external cavity semiconductor laser into an optical time lens module composed of a phase modulator and two dispersive units. The numerical results demonstrate that by properly setting the parameters of the driving signal of phase modulator and the accumulated dispersion of dispersive units, the relaxation oscillation in chaos can be eliminated, wideband chaos generation with an efficient bandwidth up to several tens of GHz can be achieved, and the RF spectrum of generated chaotic signal is nearly as flat as uniform distribution. Moreover, the periodicity of chaos induced by the external cavity modes can be simultaneously destructed by the optical time lens module, based on this the time delay signature can be completely suppressed.

Generation of wideband chaos with suppressed time-delay signature by delayed self-interference

We demonstrate experimentally and numerically a method using the incoherent delayed self-interference (DSI) of chaotic light from a semiconductor laser with optical feedback to generate wideband chaotic signal. The results show that, the DSI can eliminate the domination of laser relaxation oscillation existing in the chaotic laser light and therefore flatten and widen the power spectrum. Furthermore, the DSI depresses the time-delay signature induced by external cavity modes and improves the symmetry of probability distribution by more than one magnitude. We also experimentally show that this DSI signal is beneficial to the random number generation.

Wideband chaos generation using a delayed oscillator and a two-dimensional nonlinearity induced by a quadrature phase-shift-keying electro-optic modulator

We present a new optoelectronic architecture intended for chaotic optical intensity generation. The principle relies on an electro-optic nonlinear delay dynamics, where the nonlinearity originates from an integrated four-wave optical interferometer, involving two independent electro-optic modulation inputs. Consequently, the setup involves both two-dimensional nonlinearity and dual-delay feedback dynamics, which results in enhanced chaos complexity of particular interest in chaos encryption schemes. The generated chaos observed with large feedback gains has a bandwidth ranging from 30 kHz to 13 GHz and is confirmed by numerical simulations of the proposed dynamical model and bifurcation diagram calculation.