عدنان صبار عباس العارضي

This paper introduces a new topology of multilevel inverter, which is able to operate at high performance. This proposed circuit achieves requirements of reduced number of switches, gate-drive circuits, and high design flexibility. In most cases fifteen-level inverters need at least twelve switches. The proposed topology has only ten switches. The inverter has a quasi-sine output voltage, which is formed by level generator and polarity changer to produce the desired voltage and current waveforms. The detailed operation of the proposed inverter is explained. The theoretical analysis and design procedure are given. Simulation results are presented to confirm the analytical approach of the proposed circuit. A 15-level and 31-level multilevel inverters were designed and tested at 50 Hz.

A comprehensive analysis is performed in this paper to address the effect of state of polarizations (SOPs) of associated waveforms on the performance of a dual-pump highly nonlinear fiber-based optical phase conjugation (HNLF-OPC). The analysis starts with a set of coupled nonlinear Schrödinger equations (NLSEs) for each of the two orthogonal SOPs. Approximate analytical solutions are developed under the assumption that the pumps powers control the fiber nonlinearity. This leads to approximate analytical expressions describing both fiber parametric gain and conversion efficiency due to four-wave mixing (FWM) nonlinear process.For comparison purposes, results related to the ideal case where the waveforms have the same SOP are also given. The results reveal that using equal-power orthogonal pumps will lead to polarization insensitive HNLF-OPC.

Abstract In this paper, multiple optical phase conjugation (OPC) devices were used along the optical link to improve the performance of an 8×256 Gbps polarization-division multiplexing 16-state quadrature amplitude modulation signaling, producing total bit rate of 2.048 Tbps. A 50-GHz spaced, eight-channel wavelength division multiplexing (WDM) communication system was considered using 912 km dispersion-unmanaged standard single-mode fiber link with backward distributed Raman pumps. The performance of a dual-pump highly nonlinear fiber-based OPC was investigated analytically using a set of eight nonlinear Schrödinger equations taking into account the effect of polarization. Simulation results were compared with the case of mid-span optical phase conjugation (MS-OPC) compensation scheme showing better performance in terms of achievable Q-factor, optimal signal launched power, and the total length of the transmission link. In 256 Gbps, single-channel scenario, a Q-factor improvement of 1.35 dB was achieved and the nonlinear threshold was increased by∼4 dB compared to the case of MS-OPC. Moreover, using multiple OPC led to increase the length of the transmission link by 30.7% compared with the case of MS-OPC. In 2.048 Tbps WDM system, a maximum Q-factor of 9.27 dB over the same link was obtained showing an improvement of 0.62 dB over the MS-OPC case. The simulation results were compared with published analogous experimental data showing very good agreement.