Michael J. Connelly

Wideband semiconductor optical amplifier steady-state numerical model

A wideband steady-state model and efficient numerical algorithm for a bulk InP-InGaAsP homogeneous buried ridge stripe semiconductor optical amplifier is described. The model is applicable over a wide range of operating regimes. The relationship between spontaneous emission and material gain is clarified. Simulations and comparisons with experiment are given which demonstrate the versatility of the model.

All-optical AND gate with improved extinction ratio using signal induced nonlinearities in a bulk semiconductor optical amplifier

An all-optical AND gate based on optically induced nonlinear polarization rotation of a probe light in a bulk semiconductor optical amplifier is realized at a bit rate of 2.5Gbit/s. By operating the AND gate in an up and inverted wavelength conversion scheme, the extinction ratio is improved by 8dB compared with previously published work.

Wide-Band Steady-State Numerical Model and Parameter Extraction of a Tensile-Strained Bulk Semiconductor Optical Amplifier

A wide-band steady-state model of a tensile-strained bulk InGaAsP semiconductor optical amplifier is described. An efficient numerical algorithm of the steady-state model and a parameter extraction algorithm based on the Levenberg-Marquardt method are described. The parameter extraction technique is used to determine the material Auger recombination coefficient, effective intraband lifetime, the average strain and molar fraction of Arsenic in the active region. Simulations and comparisons with experiment are given which demonstrate the accuracy and versatility of the model

Signal-induced birefringence and dichroism in a tensile-strained bulk semiconductor optical amplifier and its application to wavelength conversion

Signal-induced birefringence and dichroism in a tensile-strained bulk semiconductor optical amplifier (SOA) are demonstrated in a counterpropagation scheme. The polarization azimuth rotation and the change of ellipticity angle of the probe light are presented on the Poincare/spl acute/ sphere and can be calculated by the Stokes parameters. All-optical wavelength conversion (inverted/noninverted and upconversion/downconversion) based on cross polarization modulation (XPolM) in SOAs are investigated. It is shown that a bit error rate (BER) of <10/sup -9/ can be achieved and an extinction ratio of > 9 dB can be obtained at a bit rate of 2.488 Gb/s with a 2/sup 31/-1 non-return-to-zero (NRZ) pseudorandom bit sequence (PRBS). Because of the larger birefringence effect induced by the pump light in the longer wavelength range, upconversion shows better performance than downconversion. Compared with the noninverted case, inverted wavelength conversion shows better performance due to the positive contribution from cross gain modulation (XGM), which takes place simultaneously with XPolM.

Comprehensive Finite-Difference Time-Dependent Beam Propagation Model of Counterpropagating Picosecond Pulses in a Semiconductor Optical Amplifier

In this paper, we present a numerical model to study counter pulse propagation in semiconductor optical amplifiers. An improved finite-difference beam propagation method for solving the modified nonlinear Schrodinger equation is applied for the first time in the counterpropagation regime. In our model, group velocity dispersion, two-photon absorption, ultrafast nonlinear refraction, and the change in the gain peak wavelength with carrier density are included, which have not been considered simultaneously in previous counterpropagation models. The model is applied to demonstrate how a subpicosecond and picosecond probe pulse shape and spectrum can be modified by a counterpropagating pump pulse. Based on the results obtained by this model, while subpicosecond probe pulses can be compressed by in this scheme, their time-bandwidth product are also improved significantly. Furthermore, the effects of several parameters are analyzed to obtain the proper probe spectral peak shift using counterpropagating probe pulses. The accuracy and computational efficiency of the new scheme are assessed through numerical examples and are shown to be superior to previously published approaches.

A Poincaré approach to investigate nonlinear polarization rotation in semiconductor optical amplifiers and its Application to all- optical wavelength conversion

Nonlinear polarization rotation (NPR) in semiconductor optical amplifiers (SOAs) is initially investigated. The changes of ellipticity angle of the probe light in a counter-propagation scheme are presented on the Poincaré sphere, and agree with the numerical simulations. All-optical wavelength conversions based on NPR in SOAs are realized at a bit rate of 2.5Gbit/s.

Digital synthetic-heterodyne interferometric demodulation

Synthetic-heterodyne demodulation is a very useful technique for signal detection in interferometric sensors. The demodulation process is usually accomplished using analogue circuits. Improved functionality can be obtained by using a digital signal processor. In this paper, an expression is derived for the sensor sensitivity where both laser phase noise and signal acquisition quantization noise are considered. The demodulation technique requires modulation of the laser frequency, usually accomplished by modulation of the laser current. An expression is derived for the second-harmonic distortion caused by the laser power modulation. The detection scheme was implemented on a digital signal processor and used to detect dynamic pressure signals with a bandwidth of 550 Hz.

Semiconductor Optical Amplifier Pattern Effect Suppression Using a Birefringent Fiber Loop

The capability of a birefringent fiber loop to suppress the pattern effect in a semiconductor optical amplifier is experimentally demonstrated. The results verify that compared to direct signal amplification this scheme achieves reduced amplitude modulation, enhanced eye diagram extinction ratio, pulse reshaping, tolerance to long string of spaces, low power penalty, and extended input power dynamic range.

40 Gb/s NRZ-DQPSK Data All-Optical Wavelength Conversion Using Four Wave Mixing in a Bulk SOA

Differential quadrature phase shift keying (DQPSK) modulation has become particularly attractive in high-speed optical communications because of its resistance to fiber nonlinearities and its more efficient use of fiber bandwidth. Because of its wavelength conversion ability, semiconductor optical amplifier (SOA) four wave mixing effect has attracted much attention. We experimentally study the FWM wavelength conversion of 40 Gb/s (20 GBd) NRZ-DQPSK data. A bulk SOA with 21 dB gain and 10 dBm output saturation power is used. The Q-factors of the input and wavelength converted signal are measured. Some signal regeneration properties are shown. A Q-factor improvement up to 1.7 dB is observed.

Reflective Semiconductor Optical Amplifier Pulse Propagation Model

A simple time-domain model for optical pulse propagation in a reflective semiconductor optical amplifier (RSOA) is described. The RSOA saturation energy, effective carrier lifetime, and spectral hole-burning parameters used in the model are determined using experimental measurements of the input and output pulse temporal profiles to the RSOA and least mean-square fitting. The model accurately predicts the propagation of 39.6 ps pulsewidth variable energy pulses in the RSOA. The model is used to predict the RSOA gain dynamics, spatial dependence of the pulse shape, and dynamic chirp.