Ammar Sharaiha

All-optical logic NOR gate using two-cascaded semiconductor optical amplifiers

The authors present a novel all-optical logic NOR gate using two-cascaded semiconductor optical. amplifiers (SOAs) in a counterpropagating feedback configuration. This configuration accentuates the gain nonlinearity due to the mutual gain modulation of the two SOAs. The all-optical NOR gate feasibility has been demonstrated delivering an extinction ratio higher than 12 dB over a wide range of wavelength.

Performances of a Photonic Microwave Mixer Based on Cross-Gain Modulation in a Semiconductor Optical Amplifier

The key goal of this paper consists of a theoretical and an experimental performances analysis of a photonic microwave mixer used as a signal down- and up-converter based on cross-gain modulation in a semiconductor optical amplifier (SOA). We give, by a small-signal analysis approach, the analytical equations of the output optical power carrying the down- and up-converted signal. Simplified formulas are developed, relating the mixing conversion gain to the modeling parameters of the SOA. The efficiency of the photonic microwave mixer based on an SOA has been evaluated in terms of mixing conversion gain, third-order input intercept point, and electrical phase noise. In addition, a subcarrier modulated by a QPSK, a 16 quadratic-amplitude modulation (QAM) and a 64 QAM at a data rate of 270 ksymb/s has been down converted from 1 GHz to 100 MHz with a low error vector magnitude of about 3.5%.

Spectral properties of amplified spontaneous emission in semiconductor optical amplifiers

We present a theoretical investigation of the spectral properties of spontaneous emission in semiconductor optical amplifiers. We use an extended (3/spl times/3) transfer matrix formalism to derive in the spectral domain an expression for the total longitudinally averaged internal field, which is valid regardless of the levels of optical input and bias current. The material parameters are saturated not only by the monochromatic signal, but also by the amplified spontaneous emission, filtered into the resonance modes of the structure, and integrated over its whole spectral range.

Semiconductor optical amplifier used as an in-line detector with the signal DC-component conservation

We present in this paper a dc-coupled in-line optical detector based on a multisection semiconductor optical amplifier (SOA). The key principle is to use a voltage reference correlated with the bias voltage level by the way of a two-section or a three-section SOA. So, by means of the differential detection, the signal dc-component is kept with reduced sensitivity to temperature and bias current fluctuations. Experimental and theoretical results are presented when a two-section SOA is used and performance predictions when a three-section is employed. The obtained responsivity is -63 VNV at 40 mA and over -110 VNV at 50 mA when the input optical power, measured within the fiber, is -13 dBm. When the SOA is biased at 40 mA, the detection bandwidth is over 1 GHz when the input optical power is -4 dBm.

Semiconductor Optical Amplifier Studies Under Optical Injection at the Transparency Wavelength in Copropagative Configuration

We experimentally and theoretically demonstrate the semiconductor optical amplifier (SOA) gain recovery-time (RT) dependence on the probe signal wavelength and power when injecting a continuous-wave high-power assist light in the device. In our paper, pump, probe, and assist-light waves are all copropagative. Experimental and numerical results show that the gain RT is significantly reduced over a wideband of probe wavelengths due to the assist-light use. The reduction is more pronounced for low probe powers. A theoretical evaluation of the transparency-wavelength dependence on both the probe wavelength and power is presented. Then, a study on assist-light power effects on the SOA dynamics as well as pump- and probe-wavelength effects on SOA gain RT is performed

Experimental and Simulation Analysis of the Third-Order Input Interception Point in an All-Optical RF Mixer Based on a Semiconductor Optical Amplifier

We present an experimental and computing analysis of the nonlinear distortions of an all-optical radiofrequency mixer based on cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA). Such an all-optical mixer is well suited for radio-over-fiber (RoF) applications. The simulation results are based on a SOA model developed under ADS™ software and are compared to experimental results in various cases. The good correlation between experimental and simulation results permits to demonstrate the ability of our SOA model to study mixing phenomenon by using a Harmonic Balance (HB) simulation method. Optical third-order input intercept point (IIP3) and its electrical equivalent are determined experimentally and by simulation with a good concordance. An optical IIP3 of -5 dBm and a spurious free dynamic range (SFDR) of 85.7 dB/Hz are obtained for a radiofrequency signal at 1 GHz. Moreover, simulations show that the IIP3 increases, all other parameters being equal, when the SOA active zone is shortened.

Theoretical investigations of quantum-dot semiconductor optical amplifier enabled intensity modulation of adaptively modulated optical OFDM signals in IMDD PON systems

Extensive explorations are undertaken, for the first time, of the feasibility of utilizing quantum-dot semiconductor optical amplifier intensity modulators (QD-SOA-IMs) in cost-sensitive intensity-modulation and direct-detection (IMDD) passive optical network (PON) systems based on adaptively modulated optical orthogonal frequency division multiplexing (AMOOFDM). A theoretical QD-SOA-IM model is developed, based on which optimum QD-SOA-IM operating conditions are identified together with major physical mechanism considerably affecting the system performance. It is shown that, in comparison with previously reported SOA-IMs in similar transmission systems, QD-SOA-IMs cannot only considerably improve the AMOOFDM transmission performance but also broaden the dynamic range of optimum operating conditions. In particular, for achieving signal bit rates of >30Gb/s over >60km single mode fiber (SMF), QD-SOA-IMs offer a 10dB reduction in CW optical input powers injected into the modulators. In addition, QD-SOA-IMs can also be employed to compensate the chromatic dispersion effect.

Towards energy-proportional clouds partially powered by renewable energy

With the emergence of the Future Internet and the dawning of new IT models such as cloud computing, the usage of data centers (DC), and consequently their power consumption, increase dramatically. Besides the ecological impact, the energy consumption is a predominant criterion for DC providers since it determines the daily cost of their infrastructure. As a consequence, power management becomes one of the main challenges for DC infrastructures and more generally for large-scale-distributed systems. In this paper, we present the EpoCloud prototype, from hardware to middleware layers. This prototype aims at optimizing the energy consumption of mono-site Cloud DCs connected to the regular electrical grid and to renewable-energy sources.

The EPOC project: Energy proportional and opportunistic computing system

With the emergence of the Future Internet and the dawning of new IT models such as cloud computing, the usage of data centers (DC), and consequently their power consumption, increase dramatically. Besides the ecological impact, the energy consumption is a predominant criteria for DC providers since it determines the daily cost of their infrastructure. As a consequence, power management becomes one of the main challenges for DC infrastructures and more generally for large-scale distributed systems. In this paper, we present the EPOC project which focuses on optimizing the energy consumption of mono-site DCs connected to the regular electrical grid and to renewable energy sources.

Pulse shape pre-distortion for improving the power efficiency of SOA-based IR-UWB over fiber systems

With the view to achieve a reach extension, the use of a Semiconductor Optical Amplifier (SOA) is investigated here for Impulse Radio Ultra Wide Band (IR-UWB) over fiber systems. Due to the nonlinear effects occurring when the amplifier operates in its saturated region, designing pulse shapes appears to be challenging for such systems. By calibrating the key parameters of some Gaussian pulses based on the photo-detected spectrum, and by considering a highly accurate SOA model, we show that a significant power efficiency improvement can be achieved. In particular, it is demonstrated that an efficiency greater than 50% can be reached with Abrahas linear sum of modified doublets, while operating at a strongly saturated point (0 dBm input power). Moreover, we examine the benefits of the proposed pre-distortion scheme in presence of 1.6 Gbps-OOK and 0.8 Gbps-PPM modulation formats, significant performance gains being obtained over a large transmission distance.