Kyriakos E. Zoiros

Ultrafast pattern-operated all-optical Boolean XOR with semiconductor optical amplifer-assisted Sagnac switch

All-optical Boolean XOR operation is demonstrated on pseudo-data patterns at 20 Gb/s with a three optical input semiconductor optical amplifier-assisted Sagnac switch. Bit pattern switching has been achieved with low energies of the incoming clock and data pulses and low pattern dependence on the switched-out pulses.

Numerical simulation of semiconductor optical amplifier assisted sagnac gate and investigation of its switching characteristics

The switching characteristics of a semiconductor optical amplifier (SOA)-assisted Sagnac gate are analyzed in terms of their critical performance parameters for full duty cycle operation from 10 to 40 GHz. Within this frame, the influence of the control pulse width, as well as of the SOA gain recovery time on the switching energy and the contrast ratio, is examined through numerical simulation. The obtained results show that full switching operation at 40 GHz or higher is feasible either by deploying gain recovery reduction techniques in bulk SOAs, or other alternative technologically advanced optical devices, such as quantum-dot SOAs.

All-Optical XOR Gate Using Single Quantum-Dot SOA and Optical Filter

In this paper, we propose to implement an all-optical XOR gate for 160 Gb/s return-to-zero data signals using a single quantum-dot semiconductor optical amplifier (QD-SOA) assisted by a detuned optical filter (OF). These two elements are connected in series in a probe-dual pump configuration. By conducting numerical simulations, we thoroughly investigate and assess the impact of the critical performance parameters on the Q2-factor. The analysis of the obtained results against this metric enables us to specify the data signals peak power, QD-SOA small signal gain, current density, electron relaxation time from the excited state to the ground state and linewidth enhancement factor, and OF detuning, bandwidth and shape, for which the XOR logic is executed at the target data format and rate both with logical correctness and high quality. The confirmation of its design feasibility combined with its simplicity and ultrafast capability makes the XOR gate scheme promising for exploitation in all-optical signal processing and switching applications.

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.

On the Feasibility of 320 GB/S All-Optical and Gate Using Quantum-Dot Semiconductor Optical Amplifier-Based Mach-Zehnder Interferometer

The feasibility of realizing an all-optical AND gate for 320Gb/s return-to-zero data by incorporating quantum-dot semiconductor optical ampliflers (QD-SOAs) in a Mach-Zehnder interferometer (MZI) is theoretically investigated and demonstrated. The proposed scheme employs the QD-SOA-based MZI in a conflguration where the QD-SOA in one MZI arm is subject to the flrst data sequence, the QD-SOA in the other MZI arm receives no such input but is constantly held in the small signal gain regime, and the second data stream is inserted from the common MZI port acting as enabling or disabling signal. Compared to other approaches adopted for the same purpose this implementation is more general, direct, ∞exible and afiordable as only one strong data signal is required to control switching. By conducting numerical simulation the impact of the critical parameters on the Q-factor is thoroughly assessed. The obtained results are interpreted with the help of a complete characterization of the QD-SOA response to an ultrafast data pulse stream. This allows to specify the requirements that the critical parameters must satisfy to achieve acceptable performance. The extracted design rules are technologically realistic and ensure AND operation both with logical correctness and high quality. The outcome of the numerical treatment extends the range of Boolean functions executed with the QD-SOA-MZI module at sub-Tb/s data rates.

Design Analysis and Performance Optimization of a Lyot Filter for Semiconductor Optical Amplifier Pattern Effect Suppression

In this paper, we analyze in detail, based on numerical modeling, the use of a Lyot filter to suppress the semiconductor optical amplifier (SOA) pattern effect. By formulating a robust design strategy, which is based on defining appropriate figures of merit and making the necessary tradeoffs between them, the filter performance can be optimized in terms of the wavelength spacing and detuning of its spectral response. The results obtained from this design procedure agree with experiment and enable us to accurately quantify to what degree the Lyot filter can resolve the SOA pattern effect problem.

Performance investigation of all-optical clock recovery circuit based on Fabry-Pérot filter and semiconductor optical amplifier assisted Sagnac switch

A theoretical model is developed and exploited for characterizing the behavior of an all-optical circuit that deploys a Fabry-Perot filter (FPF) and a semiconductor optical amplifier (SOA)-assisted Sagnac switch driven by an intense continuous wave (cw) holding beam to extract the clock signal from a received ultra-fast data stream. The role of each unit is thoroughly studied, and its understanding allows us to identify the critical operational parameters, which include the cw power, the energy of the data pulses, the SOA small signal gain, carrier lifetime and linewidth enhancement factor, the Sagnac loop asymmetry, and the finesse of the FPF. By means of numerical simulation, an extensive set of diagrams is derived, and from their interpretation the impact of these key factors on the amplitude modulation of the extracted clock pulses is investigated and evaluated. This process enables us to appropriately select and combine them to ensure enhanced performance concerning the defined quality metric, first at 10 Gb/s and then at 40 Gb/s. The final outcome demonstrates the technological feasibility and effectiveness of the proposed clock recovery scheme. The obtained results may be useful for theoretically addressing various all-optical signal processing tasks, whose proper execution relies decisively on clock recovery.

Necessary temporal condition for optimizing the switching window of the semiconductor-optical-amplifier-based ultrafast nonlinear interferometer in counter-propagating configuration

A comprehensive theoretical model of the semiconductor optical amplifier (SOA)-based ultrafast nonlinear interferometer (UNI) in counter-propagating configuration is presented. The model consists of a set of equations that describe the gain and phase dynamics of an SOA deployed as the nonlinear element in an interferometric switch. By undertaking an extensive numerical analysis, the transmission response of the UNI is calculated with respect to the key temporal parameters of the SOA transit time, the time delay between the two copies of the clock signal to be switched, and the width of the control pulses that alter the SOA properties. The obtained simulation results allow us to investigate the simultaneous influence of these parameters on the switching window and effectively correlate them to derive an operational condition that must necessarily hold in order to achieve satisfactory operation. The thorough study of this condition enables us to specify the restrictions imposed on each involved parameter and extract useful design rules concerning their proper selection and combination so as to ensure optimum performance. The proposed model can provide the framework for studying more complex, combinatorial all-optical circuits of enhanced functionality in which the UNI is the core switching module.

Performance investigation of semiconductor optical amplifier-based ultrafast nonlinear interferometer in nontrivial switching mode

The feasibility of operating the semiconductor optical amplifier (SOA)–based ultrafast nonlinear interferometer (UNI) in nontrivial switching mode is methodically investigated and demonstrated. For this purpose, a comprehensive model that simulates the dynamical behavior of an SOA subject to an ultra-high-speed pseudorandom binary sequence is appropriately adapted to the case of the specific configuration. By undertaking a detailed theoretical treatment, the impact of the most important SOA parameters on the fully loaded Q-factor is thoroughly analyzed and assessed, enabling us to extract useful design rules for their proper selection so as to ensure enhanced error-free performance at the desired output port of the considered interferometric arrangement. The outcome of this effort may assist the study and implementation of all-optical circuits and subsystems of nontrivial functionality, in particular with feedback, in which the UNI employing a SOA as the nonlinear element is the core logical module.

10-GHz all-optical recirculating shift register with semiconductor optical amplifier (SOA)-assisted Sagnac switch and SOA feedback

An all-optical recirculating shift register with inverter that uses entirely semiconductor optical amplifiers (SOAs) is demonstrated operating at 10 GHz. SOAs provide nonlinear switching in a Sagnac interferometer as well as feedback amplification. The device could hold arbitrary pattern profiles recirculating stably for hours. This demonstration also proves the cascadability of the SOA-assisted Sagnac switch up to 10 GHz.