Sensitive seismic sensors based on microwave frequency fiber interferometry in commercially deployed cables.

The use of fiber infrastructures for environmental sensing is attracting global interest, as optical fibers emerge as low cost and easily accessible platforms exhibiting a large terrestrial deployment. Moreover, optical fiber networks offer the unique advantage of providing observations of submarine areas, where the sparse existence of permanent seismic instrumentation due to cost and difficulties in deployment limits the availability of high-resolution subsea information on natural hazards in both time and space. The use of optical techniques that leverage pre-existing fiber infrastructure can efficiently provide higher resolution coverage and pave the way for the identification of the detailed structure of the Earth especially on seismogenic submarine faults.

Observation of flat chaos generation using an optical feedback multi-mode laser with a band-pass filter.

We demonstrate experimentally that flat and broadband chaotic signals can be easily generated by combining a multi-mode laser diode subject to optical feedback with a band-pass filter. Measurements are made of the RF spectra of multi-mode and single-mode outputs from an external cavity Fabry-Perot (FP) semiconductor laser before and after the filtering procedure. In this way it is found that in the chaos regime the low-frequency energy of the single-mode output is enhanced by about 25 dB comparing with that of the multi-mode output.

Parallel optical random bit generator.

We present an optical approach for high-speed parallel random bit generation based on stochastic pulse-to-pulse fluctuation in the supercontinuum (SC). Through spectrally demultiplexing the SC pulse sequence into different wavelength channels, we simultaneously extract multiple independent fast random bit streams from each SC pulse subsequence via associated comparators in parallel. Proof-of-concept experiments demonstrate that using our method, four 10 Gb/s random bit streams are obtained from a SC pulse source with verified randomness.

Towards precise one-way fiber-based frequency dissemination using phase-sensitive amplification.

In this Letter, we conceptually demonstrate the potential of a phase-sensitive amplifier to operate as an active detector of stochastic phase changes in fiber-based frequency dissemination systems with two orders of magnitude better sensitivity than state-of-the-art one-way systems relying on two-wavelength dissemination schemes. Theoretical and experimental analyses show that these stochastic phase changes (caused by environmental changes, e.g.

Artificial Neuron Based on Integrated Semiconductor Quantum Dot Mode-Locked Lasers.

Neuro-inspired implementations have attracted strong interest as a power efficient and robust alternative to the digital model of computation with a broad range of applications. Especially, neuro-mimetic systems able to produce and process spike-encoding schemes can offer merits like high noise-resiliency and increased computational efficiency. Towards this direction, integrated photonics can be an auspicious platform due to its multi-GHz bandwidth, its high wall-plug efficiency and the strong similarity of its dynamics under excitation with biological spiking neurons.

Broadband telecom to mid-infrared supercontinuum generation in a dispersion-engineered silicon germanium waveguide.

We demonstrate broadband supercontinuum generation (SCG) in a dispersion-engineered silicon-germanium waveguide. The 3 cm long waveguide is pumped by femtosecond pulses at 2.4 μm, and the generated supercontinuum extends from 1.

High-speed all-optical pattern recognition of dispersive Fourier images through a photonic reservoir computing subsystem.

In this Letter, we present and fully model a photonic scheme that allows the high-speed identification of images acquired through the dispersive Fourier technique. The proposed setup consists of a photonic reservoir-computing scheme that is based on the nonlinear response of randomly interconnected InGaAsP microring resonators. This approach allowed classification errors of 0.

Two-mode injection-locked FP laser receiver: a regenerator for long-distance stable fiber delivery of radio-frequency standards.

We propose and experimentally validate a new cost-effective optical receiver-regenerator scheme for long-distance microwave-frequency standard dissemination, based on the properties of dual-wavelength injection locked Fabry-Perot (FP) lasers. The regenerator FP laser is injection locked to one of its longitudinal modes by the incoming intensity-modulated light carrying the microwave-frequency standard. The light of a local CW laser is also injected in the regenerator FP, locking it to an adjacent mode.

Towards nonlinear conversion from mid- to near-infrared wavelengths using Silicon Germanium waveguides.

We demonstrate the design, fabrication and characterization of a highly nonlinear graded-index SiGe waveguide for the conversion of mid-infrared signals to the near-infrared. Using phase-matched four-wave mixing, we report the conversion of a signal at 2.65 µm to 1.

All-optical demultiplexing of 16-QAM signals into QPSK tributaries using four-level optical phase quantizers.

The potential of four-level optical phase quantizers toward coherent processing of advanced modulation formats, such as 16-QAM, is proposed and numerically demonstrated. The work shows that phase quantization achieved in fiber-based phase-sensitive amplifiers can demultiplex 16-QAM into two quadrature phase shift keying (QPSK) signals, enabling subchannel switching. The numerical study highlights the impact of the quantizer transfer function on the performance of the demultiplexing process and numerically calculates the bit error rate for each QPSK tributary after the demultiplexing procedure.

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.

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.

Phase synchronization scheme for a practical phase sensitive amplifier of ASK-NRZ signals.

We present a phase locking scheme that enables the demonstration of a practical dual pump degenerate phase sensitive amplifier for 10 Gbit/s non-return to zero amplitude shift keying signals. The scheme makes use of cascaded Mach Zehnder modulators for creating the pump frequencies as well as of injection locking for extracting the signal carrier and synchronizing the local lasers. An in depth optimization study has been performed, based on measured error rate performance, and the main degradation factors have been identified.

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.

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.

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.

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.

Hurst exponents and cyclic scenarios in a photonic integrated circuit.

We experimentally report the cyclic scenario of birth and annihilation of periodic orbits in a photonic integrated circuit as the feedback phase of the electric field varies. The latter is also shown to result in minimal alterations in the statistical properties of the chaotic attractor, with simultaneously transiting the Hurst exponent H , erratically, below and above the critical value of H=0.5 that indicates regular Brownian motion.

Subcarrier modulation in all-optical chaotic communication systems.

The enhancement of the encryption properties of chaotic signals generated by a semiconductor laser subject to optical feedback is numerically demonstrated by applying subcarrier modulation. The numerical analysis shows that the message can be very efficiently encrypted when the radio frequency carrier is within the frequency range where the chaos power density is maximized. Decoding performance is also numerically assessed considering both open- and closed-loop schemes at the receiver side.