A. Sharaiha

Equivalent circuit model for multi-electrode semiconductor optical amplifiers and analysis of inline photodetection in bidirectional transmissions

A rate equation model for static and dynamic behavior for bidirectional transmission in a multisection semiconductor optical amplifier (SOA) is presented. The rate equations for each section have been implemented on an electrical simulator. Here, we have used the model to study the inline photodetection in presence of bidirectional transmission. Small signal photodetection response in presence of co- and contrapropagating signals is given. The photodetection crosstalk expression in bidirectional transmission has also been reported. Simultaneous bidirectional photodetection experiments using a three-electrode SOA show good agreement between measured crosstalk and simulated results obtained by harmonic balance method. A photodetection response nearly free of crosstalk has been obtained for certain operating conditions due to the cross gain modulation between contrapropagating signals.

Wideband Time-Domain Transfer Matrix Model Equivalent Circuit for Short Pulse Propagation in Semiconductor Optical Amplifiers

A general time-domain transfer matrix model is presented which is able to handle waves perturbed by a locally uniform medium and which is particularly well adapted to equivalent circuit implementations. We use this model for the simulation of a picosecond pulse propagating through a semiconductor optical amplifier (SOA). The signal propagation through the SOA is described by an envelope propagation equation, taking into account the optical carriers wavelength evolution (modulated wavelenght division multiplexing spectrum consideration). We present the SOA equivalent circuit and its implementation under a commercially available software. The SOA is described through the wideband definition of all parameters which makes it comparable to a real component. Simulations have been validated with experimental results over at least 60 nm. We simulate both amplitude and phase evolutions of a picosecond pulse and a continuous-wave probe at various pulses optical carrier wavelengths. We show a strong influence of the imaginary part of the complex time delay on the phase variations, and as a consequence on the additional spectral red or blue shift.

All-optical inverted and noninverted wavelength conversion using two-cascaded semiconductor optical amplifiers

A two-cascaded semiconductor optical amplifier configuration in a counterpropagating topology is proposed for an all-optical wavelength conversion operation. The attractive issue of the proposed method is that the converted signal can be obtained simultaneously with an inverted and noninverted signal. The all-optical noninverted wavelength conversion feasibility is also demonstrated delivering an extinction ratio higher than 7 dB over a wide range of wavelengths.

Experimental Validation of Numerical Simulations and Performance Analysis of a Coherent Optical-OFDM Transmission System Employing a Semiconductor Optical Amplifier

In this paper, a numerical model of Semiconductor Optical Amplifiers (SOA) is experimentally validated in terms of the Alpha Factor (αH) and the Four-Wave Mixing (FWM). Besides, a Coherent Optical-Orthogonal Frequency Division Multiplexing (CO-OFDM) simulation platform is used to confirm the good agreement between the measured and the simulated Error Vector Magnitude (EVM) of a received signal amplified by the studied SOA in an optical transmission link. In addition, the performance of the SOA on the amplification of a 10.94 Gb/s QPSK CO-OFDM signal is numerically analyzed with respect to the Amplified Spontaneous Emission (ASE) noise, the Alpha Factor, the output saturation power of the SOA and the bit rate.

Harmonic and intermodulation distortion analysis by perturbation and harmonic balance methods for in-line photodetection in a semiconductor optical amplifier

Harmonic and intermodulation distortion in a semiconductor laser amplifier (SOA) used as an in-line photodetector is predicted, by using the harmonic balance technique and the perturbation method. Experimental and theoretical results are presented up to the third order.

Analysis of the sign reversal of the photodetected signal response in a multielectrode semiconductor optical amplifier

We present a theoretical analysis and experimental results for a two-electrode (200 /spl mu/m/spl times/300 /spl mu/m) 1.5-/spl mu/m semiconductor optical amplifier (SOA) used in photodetection. The experimental results show that at a particular operating point regarding current and optical input power, a sign reversal of the photodetected signal response, and a frequency bandwidth shape modification are obtained at the SOA front contact. These results are confirmed by simulation and explained by the developed theoretical photodetection expression obtained by small signal analysis from the rate equation.

Semiconductor Optical Amplifiers in Coherent Optical-OFDM Systems

Experimental results of using a semiconductor optical amplifier (SOA) for amplification of a coherent optical-orthogonal frequency-division-multiplexing (CO-OFDM) transmission system are presented. The impact of the SOA nonlinearities on the amplification of a 10.94-Gb/s quadrature phase-shift keying CO-OFDM signal with respect to the input power, the signal wavelength, and the number of subcarriers is investigated.

Distortion analysis of the photodetection and gain spectral responses of a semiconductor optical amplifier

Theoretical and experimental results regarding harmonics photodetection and cavity power gain spectrum responses are presented. The derived analytical expressions establish the link between photodetection and cavity power gain. Second-order distortions are analyzed against the input wavelength and the average input power.

Optical Radiofrequency Signal Mixing by All-Optical Sampling Based on a Semiconductor Optical Amplifier Mach–Zehnder Interferometer

Experimental performances analysis of an optical radiofrequency signal mixer based on a semiconductor optical amplifier Mach-Zehnder Interferometer utilizing an all-optical sampling method is presented. An optical pulse source generating 21-ps width pulses at a repetition rate of 7.8 GHz samples an intensity-modulated optical carrier carrying an electrical subcarrier at the intermediate frequency 1 GHz. The efficiency of the all-optical radiofrequency mixer is evaluated in terms of mixing conversion gain and third-order input intercept point. The conversion gain varies from 14.4 dB to 20.3 dB according to the chosen frequency. In addition, the electrical subcarrier modulated by a Quadrature phase shift keying (QPSK) and a 16-quadrature amplitude modulation (QAM) signal at a data rate of 1 MSymb/s has been frequency up-converted up to 40 GHz with an error vector magnitude of 11.68% for the QPSK modulation and 10.94% for the 16-QAM.

Analysis of an Optically Controlled Nonlinear Directional Coupler

An optically controlled nonlinear directional coupler (NLDC) to be useful in optical integrated circuits has been analyzed. The optical control is achieved through the interactions between a laser beam and surrounding semiconductor medium. The effect of plasma density, laser beam wavelength and waveguide with on the performance of the coupler including critical power has been thoroughly investigated. A far better performance compared to a simple NLDC has been achieved.