Implementation of full-adder and full-subtractor based on electro-optic effect in Mach–Zehnder interferometers

Interferometric devices have drawn a great interest in all-optical signal processing for their high-speed photonic activity. Quantum-dot semiconductor optical amplifier (QD-SOA)-based gate has added a new momentum in this field to perform all-optical logic and algebraic operations. In this paper, a new and alternative scheme for all-optical half adder using two QD-SOA-based Mach-Zehnder interferometers is theoretically investigated and demonstrated. The proposed scheme is driven by the pair of input data streams for one switch between which the Boolean xor function is to be executed to produce sum-bit. Then the output of the first switch and one of the input data are utilized to drive the second switch to produce carry-bit. The impact of the peak data power as well as of the QD-SOAs current density, small signal gain, and QD-SOAs length on the ER and Q-factor of the switching outcome are explored and assessed by means of numerical simulation. The operation of the system is demonstrated with 160 Gbit/s.

Ultrafast All-Optical Half Adder Using Quantum-Dot Semiconductor Optical Amplifier-Based Mach-Zehnder Interferometer

The feasibility of implementing an ultrafast NOT gate by means of a two-input Mach–Zehnder interferometer (MZI) that employs quantum-dot semiconductor optical amplifiers (QD-SOAs) is theoretically explored and shown. For this purpose a numerical treatment is conducted by modeling the propagation of strong pulses through a QD-SOA and the resultant change of the QD-SOA gain dynamics. This procedure allows to evaluate the impact of the critical parameters on the MZI complementary output port and find which is the most appropriate way to be selected and combined. The analysis of the simulation results reveals that with the non-data driven QD-SOA constantly held in the linear gain regime, the other QD-SOA, which is perturbed by the data to be logically inverted, must be operated in a nonlinear regime. This is defined by the drop of the specific QD-SOA gain by approximately 5.5 dB from its unsaturated value, which is caused by a data peak power being 4 dB higher than its saturation input power. Moreover, in order for the design to be complete, both QD-SOAs must be of medium length, provide a maximum modal gain such that their net gain exceeds by two orders of magnitude that at transparency, be biased at moderate current density and exhibit an electron relaxation time from the excited state to the ground state as fast as possible. Provided that these conditions are satisfied then a more than adequate extinction ratio can be obtained, which ensures that Boolean NOT logic is executed at 160 Gb/s both with logical correctness and high quality using QD-SOAs in a structurally simple, power efficient and operationally flexible version of the MZI.

On the design of ultrafast all-optical NOT gate using quantum-dot semiconductor optical amplifier-based Mach–Zehnder interferometer

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.

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

With high-bandwidth and on-demand applications continuing to emerge, next-generation core optical networks will likely require significant improvements in reconfigurability and ultra-fast operations Optical signal processing overcomes the electronic bandwidth limitations with the advantages in terms of transparency and scalability We review recent progresses in all-optical signal processing potentially for ultrahigh speed systems and networks Starting from a brief overview of optical signal processing in high-speed optical systems and networks, we highlight a few key network functionalities, including optical logic operations, reconfigurable add/drop multiplexing, optical regeneration, wavelength conversion, format conversion, and phase-sensitive amplification Different techniques are investigated and discussed, employing a wide range of devices and various nonlinearities Some of experimental results are presented in both single polarization systems and polarization-division multiplexing systems

All-Optical Signal Processing for UltraHigh Speed Optical Systems and Networks

The performance of an ultrafast all-optical logic gate based on quantum-dot semiconductor optical amplifier (QD-SOA) has been theoretically analyzed in this paper. We introduce a novel approach to accelerate the gain recovery process with a control pulse (CP) using the cross-gain modulation (XGM) effect. It is shown that the optical XOR gate in a Mach-Zehnder interferometer-based structure is feasible at Tb/s speeds with proper quality factor. The operation capability at 2.5 Tb/s with a Q-factor of 4.9 and 2 Tb/s with a Q -factor of 8.8 is reported for the first time. This capability indicates great potential for ultrafast all-optical signal processing and switching.

H. Nejad

Papers

Tb/s Optical Logic Gates Based on Quantum-Dot Semiconductor Optical Amplifiers