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Taking the broadband chaotic output from a weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) under filtered feedback as a chaotic entropy source, we propose and experimentally demonstrate a scheme for generating fast physical random bits (PRBs) at a rate up to 240 Gbits/s. First, we investigate the dependence of the dynamical properties of the filtered feedback WRC-FPLD on the system parameters, and determine the optimized parameter region for generating wavelength-tunable and broadband chaotic signals. Second, a broadband chaotic signal with a bandwidth beyond 20 GHz output from the WRC-FPLD is sampled and transferred to a digital bit sequence by an 8-bit analog-to-digital converter at a rate of 40 GS/s. Finally, by utilizing multi-bit post-processing method, PRBs is generated at a rate up to 240 Gbits/s, which can pass all the 15 NIST statistics tests and meet the strict criteria of the statistical bias and the serial correlation coefficient.

We present our recent progress in the realization of heterogeneously integrated InP-on-silicon wavelength-tunable lasers that allow for fast, electronic wavelength tuning. Experimental demonstrations of discretely tunable arrayed waveguide grating lasers with filtered feedback and continuously tunable twin-guide (TTG) distributed feedback lasers are discussed. Excellent static and dynamic laser characteristics are achieved, with mW-level waveguide-coupled output powers, single-mode operation across the tuning range and direct modulation above 10 Gb/s. Measured wavelength switching times are less than a few nanoseconds, providing interesting prospects for optical packet switching applications. It is furthermore shown that a novel TTG distributed Bragg reflector laser design could further improve the wavelength tuning ranges and efficiencies obtained so far. [ABSTRACT FROM AUTHOR]

The synthesis of wavelength-tunable broadband chaotic signals is experimentally demonstrated by using a weak-resonant-cavity Fabry–Perot laser diode (WRC-FPLD) subject to filtered feedback. To perform the broadband tunability from 1544 to 1556 nm, a tunable optical filter is used for providing filtered feedback to drive the laser into chaos. With adjusting the central wavelength of the filter, about 20 longitudinal modes of the WRC-FPLD can individually realize the chaotic output within the tunable range of the filter. Moreover, by suitably selecting the feedback power, the chaos signal with a flat power spectrum and broad bandwidth up to ~30.0 GHz can be achieved. [ABSTRACT FROM PUBLISHER]

We experimentally and numerically characterize the wavelength switching speed of a tunable semiconductor ring laser using filtered optical feedback. The feedback is realized employing two arrayed-waveguide gratings to split/recombine light into different wavelength channels. The wavelength tuning and switching is controlled by changing the currents injected in semiconductor optical amplifiers in the feedback section. A wavelength switching speed of a few nanoseconds is achieved. We investigate also the effect of the feedback parameters and noise strength on the wavelength switching speed. [ABSTRACT FROM PUBLISHER]

A novel discretely tunable laser based on filtered feedback is presented. The semiconductor device consists of a Fabry--Perot laser with deeply etched broadband distributed Bragg reflector mirrors. Single-mode operation is achieved by using feedback from an integrated filter. This filter contains an arrayed waveguide grating wavelength router and a semiconductor optical amplifier gate array. Design, simulation, and the first characterization results of this new integrated filtered-feedback tunable laser device are presented. It shows a combination of a simple and robust switching algorithm with good wavelength stability. A rate equation model predicts that a properly designed device can switch within 1 ns. The fast switching and reduced control complexity makes the device very promising for various advanced applications in optical telecommunication networks. [ABSTRACT FROM PUBLISHER]

Abstract: The emission characteristics of a vertical-cavity surface-emitting laser (VCSEL) operated in a single-transverse mode and coupled to an external cavity with a diffraction grating as a frequency-selective element are analyzed experimentally, numerically and analytically. The experiments yield a rather abrupt turn-on of the VCSEL to a high-amplitude emission state and hysteresis phenomena. The experimental results are explained by numerical simulations and analytical calculations demonstrating the possibility of bistability between lasing and non-lasing states close to threshold. Hence, the scheme might be useful in all-optical photonic switching applications. A detailed bifurcation analysis near threshold is given by superimposing the numerical results with analytical steady-state curves. The mode selection and switching behavior obtained in the simulations can be interpreted from the point of view of the preference of states with the minimal total losses. [Copyright &y& Elsevier]

We report experimental results on the nonlinear dynamical response of a semiconductor laser subjected to time-delayed (>5 ns), frequency selective, optical feedback from a Fabry-Pe´rot interferometer type of filter. Three regimes of interest, based on the relative value of the filter bandwidth with respect to the relevant laser parameters (relaxation oscillation frequency and external cavity mode spacing), are identified, viz. a wide filter case, an intermediate filter width case, and a narrow filter case. The dynamical response of the laser is shown to be quite different in each of these regimes. The principal results are 1) the laser's linewidth enhancement factor, coupled with the nonlinear response of the filter, can be exploited to induce nonlinear dynamics in the instantaneous optical frequency of the laser light on a time scale related to the time-delay of the feedback, 2) a mode mismatch effect which arises from a detuning between the filter center frequency and the nearest external cavity mode and manifests itself in a reduction of the maximum light available for feedback, and 3) a reduction in, or even disappearance of, relaxation oscillations in the laser dynamics when a filter of appropriate width is chosen. More generally, it is observed that certain dynamics that occur due to unfiltered optical feedback may be suppressed when the feedback light is spectrally filtered. [ABSTRACT FROM PUBLISHER]