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.
We propose a scheme to generate wavelength-tunable broadband Optical Frequency Combs (OFCs) based on an optical injection gain-switched Weak-Resonant-Cavity Fabry-Perot Laser Diode (WRC-FPLD). Firstly, a sinusoidal signal with frequency of 1.6 GHz and power of 19 dBm is utilized to drive the WRC-FPLD into the gain-switched state. Then, external optical injection is introduced into the gain-switched WRC-FPLD for generating wavelength-tunable broadband OFCs. The experimental results demonstrate that, when the wavelength of injected light is in the middle of the two modes, the OFCs with larger bandwidth can be obtained. When the wavelength and power of the injection light are 1545.6522 nm and 3.397 μW, respectively, the maximum bandwidth of generated OFC can arrive at 76.8 GHz (49 comb lines), and the single sideband phase noise for the fundamental frequency of the beat signal is as low as -125.5 dBc/Hz@10 kHz. The coherence of comb lines increases with the decrease of modulation frequency. Through varying the wavelength of injection light and selecting the matched injection power, the central wavelength of OFC can be adjusted within the range of (1525 nm, 1565 nm).
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 propose and experimentally demonstrate a wideband multi-channel chaotic source using a Weak Resonator Cavity Fabry-Perot Laser Diode (WRC-FPLD) with Self-Phase Modulated Optical Feedback (SPMOF), in which, phase modulation is introduced into the external optical feedback loop to improve the bandwidth of the generated multi-channel chaotic signals. The experimental results show that under appropriate optical feedback intensity, WRC-FPLD with SPMOF can generate wideband multi-channel chaotic signals, when the feedback intensity is in the range of -45 dB to -15 dB, the lasing modes in the range of 1530 nm to 1570 nm can be simultaneously driven into chaos state. In addition, the Time Delay Signature (TDS) characteristics of the generated multi-channel chaotic signals are also investigated. To highlight the advantages of the proposed scheme, we also conducted comparative experiments on the conventional optical feedback scheme without phase modulation. Using SPMOF scheme, the obtained bandwidth of multi-channel chaotic signals is improved obviously, the standard bandwidth reaches 11.5 GHz, the TDS of chaotic signal is suppressed to an indistinguishable level. Relative to traditional Fabry-Perot laser diode, WRC-FPLD used in the experiment has a smaller front reflectance, about 1/90 of the rear reflectance, and a longer cavity, so it can excite more lasing modes. The proposed scheme can generate wideband multi-channel chaotic signals with a small mode spacing, which is an ideal light source for the chaotic optical communication system using wavelength division multiplexing technology.
We propose and experimentally demonstrate a stable and tunable PT-symmetric single-longitudinal-mode (SLM) fiber ring laser using a nonreciprocal Sagnac loop. To suppress multiple-longitudinal-mode oscillation, the Sagnac loop only including a 3-dB optical coupler (OC) and a polarization controller (PC) is incorporated into the fiber ring cavity, which induces nonreciprocal light transmission and coupling between the frequency-degenerate clockwise (CW) and counterclockwise (CCW) resonator modes. The two light paths traveling along the CW and CCW directions in the Sagnac loop are defined as the gain loop and loss loop, respectively. By adjusting the polarization states of the two light waves, when the gain and loss coefficients are larger than the coupling coefficient, the PT symmetry is broken, singlemode lasing is thus generated in the fiber laser cavity.
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.
Based on a weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) with dispersive optical feedback provided by a linearly chirped fiber Bragg grating (LCFBG), we propose a scheme for simultaneously generating multi-channel chaotic signal with time delay signature (TDS) suppression. The experimental results show that under LCFBG feedback, 45 longitudinal modes within a 30-dB amplitude variation in the WRC-FPLD can be simultaneously driven into chaotic states. With the increase of feedback strength, the effective bandwidth of the generated chaotic signal gradually increases while the TDS value firstly decreases and then increases. For feedback strength from -35 dB to -15 dB, the generated chaotic signals by WRC-FPLD under LCFBG feedback possess lower TDS compared with those under mirror feedback or ring cavity feedback. Under an optimized feedback strength of -32.88 dB, the TDS value is about 0.01, which means the TDS is almost completely suppressed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.