Adonis Bogris

Implementation of 140 Gb/s true random bit generator based on a chaotic photonic integrated circuit

In the present work a photonic integrated circuit (PIC) that emits broadband chaotic signals is employed for ultra-fast generation of true random bit sequences. Chaotic dynamics emerge from a DFB laser, accompanied by a monolithic integrated 1-cm long external cavity (EC) that provides controllable optical feedback. The short length minimizes the existence of external cavity modes, so flattened broadband spectra with minimized intrinsic periodicities can emerge. After sampling and quantization--without including optical de-correlation techniques and using most significant bits (MSB) elimination post-processing--truly random bit streams with bit-rates as high as 140 Gb/s can be generated. Finally, the extreme robustness of the random bit generator for adaptive bit-rate operation and for various operating conditions of the PIC is demonstrated.

First demonstration of all-optical QPSK signal regeneration in a novel multi-format phase sensitive amplifier

We propose a novel black-box optical phase sensitive amplifier (PSA) configuration and describe its application to the regeneration of multi-level phase encoded signals. The concept is demonstrated with a 10 Gbaud quadrature phase shift keyed (QPSK) input.

Chaos-on-a-chip secures data transmission in optical fiber links.

Security in information exchange plays a central role in the deployment of modern communication systems. Besides algorithms, chaos is exploited as a real-time high-speed data encryption technique which enhances the security at the hardware level of optical networks. In this work, compact, fully controllable and stably operating monolithic photonic integrated circuits (PICs) that generate broadband chaotic optical signals are incorporated in chaos-encoded optical transmission systems. Data sequences with rates up to 2.5 Gb/s with small amplitudes are completely encrypted within these chaotic carriers. Only authorized counterparts, supplied with identical chaos generating PICs that are able to synchronize and reproduce the same carriers, can benefit from data exchange with bit-rates up to 2.5Gb/s with error rates below 10(-12). Eavesdroppers with access to the communication link experience a 0.5 probability to detect correctly each bit by direct signal detection, while eavesdroppers supplied with even slightly unmatched hardware receivers are restricted to data extraction error rates well above 10(-3).

Full characterization of the signal and idler noise figure spectra in single-pumped fiber optical parametric amplifiers.

For the first time, four different noise sources, which are amplified quantum noise, Raman phonon seeded excess noise, pump transferred noise (PTN), and pump residual noise, are considered simultaneously to model the wavelength-dependent noise figure in a single-pumped fiber optical parametric amplifier. An asymmetric signal NF spectrum induced by both Raman phonon seeded excess noise and Raman gain modified PTN is measured in the electrical domain. Theoretical results agree very well with the experimental data. The idler NF spectrum is also analyzed and measured, which shows a more symmetric profile.

RZ-DPSK signal regeneration based on dual-pump phase-sensitive amplification in fibers

All-optical regeneration of differential phase-shift keying signals by means of a phase-sensitive amplification scheme solely based on highly efficient four-wave mixing in fibers is theoretically and numerically studied. The analytical and numerical investigation demonstrates almost ideal phase regeneration accompanied with enhanced amplitude noise suppression in the regime of pump depletion

Feedback Phase in Optically Generated Chaos: A Secret Key for Cryptographic Applications

The feedback phase in a chaotic system consisting of a semiconductor laser subject to delayed optical feedback is considered for the first time as a secret key for secure chaotic communications not exclusively based on hardware uniqueness. Extensive numerical simulations illustrate that the feedback phase is of extreme importance as far as synchronization is concerned. The ability of an eavesdropper to attack the intensity-modulated message when a pseudorandom variation of the feedback phase is imposed at the transmitters side is numerically quantified by bit-error-rate calculations. The analysis demonstrates that the eavesdropper is not able to synchronize and hence to extract the message when he is not aware of the phase variations even if he is equipped with an identical chaotic device.

Modeling and measurement of the noise figure of a cascaded non-degenerate phase-sensitive parametric amplifier.

Semi-classical noise characteristics are derived for the cascade of a non-degenerate phase-insensitive (PI) and a phase-sensitive (PS) fiber optical parametric amplifier (FOPA). The analysis is proved to be consistent with the quantum theory under the large-photon number assumption. Based on this, we show that the noise figure (NF) of the PS-FOPA at the second stage can be obtained via relative-intensity-noise (RIN) subtraction method after averaging the signal and idler NFs. Negative signal and idler NFs are measured, and <2 dB NF at >16 dB PS gain is estimated when considering the combined signal and idler input, which is believed to be the lowest measured NF of a non-degenerate PS amplifier to this date. The limitation of the RIN subtraction method attributed to pump transferred noise and Raman phonon induced noise is also discussed.

FWM-based wavelength conversion of 40 Gbaud PSK signals in a silicon germanium waveguide

We demonstrate four wave mixing (FWM) based wavelength conversion of 40 Gbaud differential phase shift keyed (DPSK) and quadrature phase shift keyed (QPSK) signals in a 2.5 cm long silicon germanium waveguide. For a 290 mW pump power, bit error ratio (BER) measurements show approximately a 2-dB power penalty in both cases of DPSK (measured at a BER of 10(-9)) and QPSK (at a BER of 10(-3)) signals that we examined.

Numerical Investigation of a 160-Gb/s Reconfigurable Photonic Logic Gate Based on Cross-Phase Modulation in Fibers

A simple reconfigurable all-optical logic gate based on cross-phase modulation in highly nonlinear fibers is numerically demonstrated. Fine performance at 160 Gb/s is obtained for five logic functions (xor, or, nand, nor and not). The implementation simplicity and the high-bit-rate operation make the proposed device suitable for ultrafast applications in the emerging all-optical networks

Optical properties of silicon germanium waveguides at telecommunication wavelengths

We present a systematic experimental study of the linear and nonlinear optical properties of silicon-germanium (SiGe) waveguides, conducted on samples of varying cross-sectional dimensions and Ge concentrations. The evolution of the various optical properties for waveguide widths in the range 0.3 to 2 µm and Ge concentrations varying between 10 and 30% is considered. Finally, we comment on the comparative performance of the waveguides, when they are considered for nonlinear applications at telecommunications wavelengths.