P. Lemieux

Suppression of Turbulence-Induced Scintillation in Free-Space Optical Communication Systems Using Saturated Optical Amplifiers

A laboratory-simulated free-space optical link under various turbulence levels is implemented to propose and experimentally demonstrate the use of saturated optical amplifiers as a simple and efficient approach for suppression of scintillation due to atmospheric turbulence. The use of erbium-doped fiber amplifier (EDFA) or semiconductor optical amplifier (SOA) requires the received signal be coupled into a fiber. The system performance of receiver structures employing a saturated EDFA and a SOA (in saturation and conversion modes) are measured and compared to that of fiberless direct detection (DD). It is shown that in higher turbulence levels, where no data transmission can be achieved by DD, remarkable eye opening results when using saturated amplifiers

Fast and Efficient Dynamic WDM Semiconductor Optical Amplifier Model

A novel state-variable model for semiconductor optical amplifiers (SOAs) that is amenable to block diagram implementation of wavelength division multiplexed (WDM) signals and fast execution times is presented. The novel model is called the reservoir model, in analogy with similar block-oriented models for Raman and erbium-doped fiber amplifiers (EDFAs). A procedure is proposed to extract the needed reservoir model parameters from the parameters of a detailed and accurate space-resolved SOA model due to Connelly, which was extended to cope with the time-resolved gain transient analysis. Several variations of the reservoir model are considered with increasing complexity, which allow the accurate inclusion of scattering losses and gain saturation induced by amplified spontaneous emission. It is shown that at comparable accuracy, the reservoir model can be 20 times faster than the Connelly model in single-channel operation; much more significant time savings are expected for WDM operation. The model neglects intraband SOA phenomena and is thus limited to modulation rates per channel not exceeding 10 Gb/s. The SOA reservoir model provides a unique tool with reasonably short computation times for a reliable analysis of gain transients in WDM optical networks with complex topologies

Error-free transmission for incoherent broad-band optical communications systems using incoherent-to-coherent wavelength conversion

A new method is presented to exploit the cross-gain modulation mechanism in semiconductor optical amplifiers to reduce the intensity noise of spectrum-sliced communications systems via conversion of the modulated incoherent optical signal into a coherent signal before the detection process. Wavelength-division-multiplexed networks using broad-band sources have performance limited by intensity noise; conversion from an incoherent to a coherent signal reduces the intensity noise and enables the elimination of the bit-error-rate floor.

SOA gain recovery wavelength dependence: simulation and measurement using a single-color pump-probe technique.

Measurements to date of the wavelength dependency of gain recovery time in semiconductor optical amplifiers (SOAs) have mostly used pump-probe techniques with a pump and probe operated on distinct wavelengths. Choice of pump wavelength, and its relative proximity to the probe wavelength, could influence measurements and impede unambiguous observation of wavelength dependence on recovery dynamics. We use a single-color pump-probe measurement technique to directly access the wavelength dependence of the gain recovery time in bulk InGaAsP SOAs. We used ultrashort pulses from a single mode locked laser to measure unambiguously the spectral dependency and temporal behavior of SOAs. Simulation results using a model that takes into account intra-band and inter-band contributions to SOA saturation, as well as experimental results for the SOA tested, show recovery rate dependency similar to gain spectrum.

Optimal SOA-based Noise Reduction Schemes for Incoherent Spectrum-Sliced PONs

We experimentally compare noise reduction of incoherent spectrum-sliced light using a SOA in both direct amplification and incoherent-to-coherent conversion. Results show conversion is more efficient when using fast gain recovery SOAs.

Incoherent-to-coherent wavelength conversion using semiconductor optical amplifier

This paper reports for the first time an all-optical wavelength conversion of an incoherent optical signal to a coherent optical signal using the cross-gain modulation in semiconductor optical amplifiers. Wavelength division multiplexed networks using broadband sources have performance limited by beat noise; conversion from a noncoherent to a coherent signal eliminates beat noise and enables the elimination of the bit error rate floor.

A Reservoir Dynamic Model for Linear Optical Amplifiers

A novel state-variable dynamic model for semiconductor linear optical amplifiers (LOA) is used to describe gain dynamics and stabilization properties of LOAs. Results from the model are verified against experiments

New gain parameterization for fast semiconductor optical amplifier model

Numerical simulations of semiconductor optical amplifiers (SOA) often are time consuming. Making simplifying assumptions, we obtain a fast model based on the reservoir, representing the total number of useful carriers. In this paper, we explain how this model is developed and how the gain is parameterized. We demonstrate that the scattering losses, dropped in the derivation of the reservoir model, can be re-introduced by applying a simple transformation to the gain coefficient. In this way, the accuracy of the model is greatly increased, but its level of complexity remains low.

A Novel Model for SOAs in WDM Networks

We present a novel state-variable model for semiconductor optical amplifiers, amenable to block diagram implementation, and with fast execution times

Intensity noise in incoherent-to-coherent wavelength conversion in SOAs

We examine a noise reduction scheme exploiting cross-gain modulation in SOAs to convert the incoherent received signal to a coherent signal before the detection process, thus reducing the bit error rate (BER) floor. We present experimental results on the effect on the intensity noise in a spectrum-sliced incoherent light system incorporating semiconductor optical amplifier (SOA) based noise reduction of the following key parameters: optical bandwidth, electrical bandwidth and the incoherent received power.